Assessment and Improvement of SALASALA Private Decentralized fecal sludge Management System

ASSESSMENT AND IMPROVEMENT OF SALASALA PRIVATE DECENTRALIZED

FAECAL SLUDGE MANAGEMENT SYSTEM

A dissertation

Submitted to the graduate faculty of Environmental Engineering of Ardhi University in partial

fulfillment of the requirements for the graduate degree of Bachelor of Science in Environmental

engineering

By

ULOTU GERALD

July 2012.

ENVIRONMENTAL ENGINEER DEPARTMENT

SCHOOL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY (SEST)

ARDHI UNIVERSITY

P.O.BOX 35176

Dar es Salaam

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|COPYRIGHT

iii

COPYRIGHT

This dissertation is a copyright material protected under Berne Convention, the Copyright Act

1999 and other International and National enactments in that behalf, on intellectual property. It

may not be reproduced by any means in full or in part, except for extracts in fair dealing, for

research or private study, critical scholarly review or discourse with an acknowledgement,

without written permission of the Directorate of Undergraduate Studies, on behalf of both the

Author and the Ardhi University

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|ABSTRACT

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ABSTRACT

This research set out to assess the Salasala privately operated decentralized faecal sludge

management system which located at Tegeta Dar es Salaaam and to critically analyze the

improvements which are needed to make it suitable a faecal sludge management system with a

potential for citywide adoption. Currently the Salasala privately faecal sludge management

facility is the only facility that is used to manage faecal sludge from on-site sanitation facilities

of the whole area of Tegeta Boko, Bunju, Ununio, Wazo Hill, Salasala, KunduchiMtongani,

Kunduchi, Africana and part of Mikocheni neighborhoods.

Wastewater samples was taken from the sludge pond (i.e. at the inlet, middle and outlet), and

outlet of constructed wetland system. The sludge volume of the pond was measured by

configuring onsite offshore coordinate system along the breadth and span of the pond and the

sludge depth was taken with a tape at each point X, Y of orthogonal projection and volume

computation was done by using a Spot height method of Earth work computation. Sludge

samples was taken from five sampling points, two points of three samples taken vertically down

along the sludge depth and three points of single samples in the sludge pond. Analysis of

physicochemical characteristics such Color, Turbidity, Total suspended solid and ammonia

nitrogen of system wastewater was observed to be not within the minimum permissible amounts

(i.e. TBS and WHO).The parameters of effluent wastewater that observed to be far away from

the standards was Color, 900Pt-Co/L where’s TBS standards is 300Pt-Co/L, Turbidity 500NTU

(TBS standards 300) and TSS 251.5 mg/L (TBS standards 100 mg/L). Chemical parameters,

Ammonia-nitrogen (NH3-N) was 200mg/l where’s TBS standards is 6mg/L, and a phosphate

PO4 129.67 mg/L where’s TBS standards is 15 mg/L. Biological characteristic of effluent

wastewater such as COD, BOD5, Faecal coliform and total coliforms was totally not within either

TBS or WHO standards. COD and BOD5 was 636.67 mg/L and 318.33 mg/L where’s TBS

standards are 60 and 30 mg/L respectively. Faecal coliforms and Total coliforms was 16 × 106

and 22 × 106 count/100 mL where’s TBS standards are 1000 and 10000 count/100mL

respectively. For sludge volume and stability test, it was observed that the pond have a sludge

volume of 252 m3 and the sludge have not yet stabilized enough. The system looks economical,

as it makes a profit of about 51,840,000 Tsh/= per year, However the system improvements

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|TABLE OF CONTENTS

vii

should be made to increase its performance in wastewater and sludge treatment as well a

profit/year as per analysis, it does not effective recovers all resources suitably obtained through

sludge treatment.


viii

TABLE OF CONTENTS

CERTIFICATION......................................................................................................................... i

DECLARATION........................................................................................................................... ii

COPYRIGHT............................................................................................................................... iii

DEDICATION.............................................................................................................................. iv

ACKNOWLEDGEMENTS ......................................................................................................... v

ABSTRACT.................................................................................................................................. vi

TABLE OF CONTENTS .......................................................................................................... viii

LIST OF FIGURES ................................................................................................................... xiii

LST OF TABLES....................................................................................................................... xiv

LIST OF PLATES ...................................................................................................................... xv

ACRONYMS AND ABBREVIATION.................................................................................... xvi

CHAPTER ONE ........................................................................................................................... 1

1.0 GENERAL INTRODUCTION............................................................................................. 1

1.1 Justification and Motivation.................................................................................................. 3

1.2 Research problem.................................................................................................................. 3

1.3 Objective of the Study........................................................................................................... 4

1.3.1 Specific objectives .......................................................................................................... 4

1.4 Scope ..................................................................................................................................... 4

1.5 Expected output..................................................................................................................... 4

CHAPTER TWO .......................................................................................................................... 5

LITERATURE REVIEW............................................................................................................ 5

2.1 Fecal Sludge .......................................................................................................................... 5

2.1.1 Sewage sludge ................................................................................................................ 5


ix

2.1.2 Faecal sludge characteristics .......................................................................................... 6

2.1.3 Nutrients in sludge.......................................................................................................... 7

2.2 Domestic wastewater............................................................................................................. 9

2.2.1 Domestic waste Water Characteristics ......................................................................... 11

2.3 Faecal Sludge Treatment..................................................................................................... 14

2.3.1 Solids/liquid separation ................................................................................................ 15

2.3.2 Gravity solids/liquid separation.................................................................................... 15

2.3.3 Mechanical solids/liquid separation ............................................................................. 16

2.3.4 Digestion....................................................................................................................... 17

2.3.5 Anaerobic Decomposition ............................................................................................ 17

2.4 Wetlands and sludge treatment ........................................................................................... 18

2.4.1 Natural wetland............................................................................................................. 18

2.4.2 Constructed wetland ..................................................................................................... 19

2.5 Biological processes in CWs............................................................................................... 27

2.6 Chemical processes ............................................................................................................. 28

2.7 Physical processes ............................................................................................................... 28

2.8 Process rates ........................................................................................................................ 28

2.9 Hydrological limitations...................................................................................................... 28

2.10 Wetland nitrogen processes............................................................................................... 29

2.11 Wetland in Phosphorus removal ....................................................................................... 30

2.12 CWs in Suspended solids removal .................................................................................... 31

2.13 CWs in Pathogen removal................................................................................................. 31

2.14 CWs in Heavy metal removal ........................................................................................... 31

2.15 Abiotic Factors and their Influence on Wetlands.............................................................. 32

2.15.1 Oxygen........................................................................................................................ 32


x

2.15.2 pH ............................................................................................................................... 32

2.15.3 Temperature................................................................................................................ 32

2.16 Sludge drying .................................................................................................................... 33

2.16 Sludge composting ............................................................................................................ 34

2.16.1 Advantages of composting ......................................................................................... 35

CHAPTER THREE.................................................................................................................... 36

MATERIALS AND METHODS.............................................................................................. 36

3.0 Location of the study area ............................................................................................... 36

3.1 Climatic condition ........................................................................................................... 38

3.2 Existing situation ............................................................................................................. 38

3.2.1 System description........................................................................................................ 39

3.3 Materials.............................................................................................................................. 43

3.3.1Sludge depth measurements .......................................................................................... 43

3.3.2 Wastewater Sampling ................................................................................................... 43

3.3.3 Faecal sludge sampling................................................................................................. 44

3.3.3 Equipment’s used ......................................................................................................... 45

3.3.4 Reagents used ............................................................................................................... 45

3.4 Methods............................................................................................................................... 46

3.4.1 Site visits and interview................................................................................................ 46

3.4.2 Experimental setup for sludge stability ........................................................................ 46

3.4.3 Analysis ........................................................................................................................ 47

3.4.3.1 Physical parameters ................................................................................................... 47

3.4.3.2 Chemical parameters ................................................................................................. 47

3.4.3.3 Chemical Oxygen Demand........................................................................................ 49

3.4.3.4 Faecal and Total coliforms (FC &TC) ...................................................................... 49


xi

3.4.3.5 Data analysis and computations ................................................................................ 49

CHAPTER FOUR....................................................................................................................... 50

DATA RESULTS AND DISCUSSION ................................................................................... 50

4.1 Wastewater characteristics .................................................................................................. 50

4.1.1 Physical Characteristics ................................................................................................ 50

4.1.2 Chemical characteristics ............................................................................................... 57

4.1.3 Biological characteristics.............................................................................................. 59

4.2 Pond Sludge stability and volume....................................................................................... 62

4.2.1Pond Sludge stability ..................................................................................................... 62

4.2.2 Sludge volume determination ....................................................................................... 64

4.3 Economic aspect of Salasala faecal sludge management system........................................ 66

4.4 Aesthetics assessment ......................................................................................................... 68

4.4.1Solid waste management................................................................................................... 68

4.4.2 Odor and smell.............................................................................................................. 68

4.4.3 Surrounding Land Use.................................................................................................. 69

4.4.4 Insect Attraction ........................................................................................................... 69

4.4.5 Personal protective equipment’s (PPE’s) ..................................................................... 70

4.5 System improvements required........................................................................................... 71

4.5.1General improvements................................................................................................... 71

4.5.1.1 Land use round system plant. .................................................................................... 71

4.5.1.2 Solid waste management at the system plant ............................................................ 71

4.5.1.3 Unit of sludge dewatering.......................................................................................... 71

4.5.1.4 Aesthetic and beauty of the surroundings system environment ................................ 71

4.5.1.5 Improvement’s to make Salasala faecal sludge management system cost effective . 72

4.5.2 Specific improvements..................................................................................................... 73

ARDHI UNIVERSITY Dissertation by Ulotu Gerald |LISTOF FIGURES

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4.5.2.1 Constructed wetland system improvements .............................................................. 73

4.5.2.2 Sludge pond improvements ....................................................................................... 73

CHAPTER FIVE ........................................................................................................................ 75

5.0 CONCLUSION ................................................................................................................... 75

5.1 RECOMMENDATION .......................................................................................................... 76

REFERENCES............................................................................................................................ 77

REFERENCES............................................................................................................................ 78

APPENDIXES............................................................................................................................. 80

Appendix 01: AVERAGE PHYSICAL CHARACTERISTICS OF WASTEWATER........ 81

Appendix 02: AVERAGE CHEMICAL CHARACTERISTICS OF WASTEWATER...... 82

Appendix 03: AVERAGE BIOLOGICAL CHARACTERISTICS OF WASTEWATER .. 83

Appendix 04: GAS VOLUME IN mL OF SLUDGE STABILITY TEST............................. 84

Appendix 05: SALASALA POND SLUDGE DEPTH AND VOLUME RESULTS............. 85

Appendix 06: RAW DATA OF PHYSICOCHEMICAL PARAMETERS ........................... 86

Appendix 07: LONGITUDINAL SLUDGE PROFILE OF THE POND...…………….…...88

Appendix 08: CROSS SECTIONAL SLUDGE PROFILE OF THE POND……………….89

Appendix 09: PICTURES DURING WASTEWATER ANALYSIS ..................................... 90

ARDHI UNIVERSITY Dissertation by Ulotu Gerald |LISTOF FIGURES

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LIST OF FIGURES

Figure 2.1: Factors influencing FS characteristics.......................................................................... 6

Figure 2.3: Emergent macrophytes treatment system with surface flow...................................... 20

Figure 2.4: Emergent macrophytes treatment system with horizontal sub surface flow .............. 21

Figure 2.5: Section through Horizontal surface Flow Constructed Wetland................................ 25

Figure 3.0: Topographical map of the study area…………………………………………..……24

Figure 3.1 Schematic diagrams of Salasala Faecal sludge treatment system ............................... 38

Figure 3.2 Wastewater sampling points………………………………………………………….44

Figure 3.3 Faecal sludge sampling points................................................................................... 44

Figure 3.4 Schematic diagram of typical experimental setup....................................................... 46

Figure 4.1 PH variations along the treatment plant. ..................................................................... 53

Figure 4.2 Temperature variations along the treatment plant ....................................................... 53

Figure 4.3 TDS variation along the treatment plant ..................................................................... 54

Figure 4.5 Conductivity variations along the treatment plant....................................................... 55

Figure 4.6 Salinity variations along the treatment plant ............................................................... 55

Figure 4.8 Colour variations along the treatment plant ................................................................ 56

Figure 4.9 Turbidity variations along the treatment plant ............................................................ 56

Figure 4.10 Ammonia-nitrogen variations along the treatment plant........................................... 58

Figure 4.11 Phosphate variations along the treatment plant ......................................................... 58

Figure 4.12 BOD5 variations along the treatment plant ............................................................... 60

Figure 4.14 Total coliforms variations along the treatment plant................................................. 61

Figure 4.15 Faecal coliforms variations along the treatment plant............................................... 61

Figure 4.16 Sludge stability progress for different sludge sample ............................................... 63

Figure 4.17 Cumulative gas volume of the sludge sample ........................................................... 64

Figure 4.18 Pond coordinate configuration .................................................................................. 65

ARDHI UNIVERSITY Dissertation by Ulotu Gerald |LSTOF TABLES

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LST OF TABLES

Table 2.1: Characteristics of faecal sludge’s .................................................................................. 7

Table 2.2 Human excreta per capita quantities and their resource value........................................ 8

Table 2.3 Typical composition of untreated domestic wastewater ................................................ 9

Table 2.4 Composition of human faeces and urine ...................................................................... 11

Table 2.5 Vegetation type and water column contact in constructed wetlands ............................ 21

Table 2.6 Pollutant removal mechanisms in constructed wetlands ............................................. 22

Table 2.7 Wetland zones and their associated components .......................................................... 24

Table 2.8: Overview of pollutant removal mechanisms ............................................................... 25

Table: 4.5 Economic analysis of salasala faecal sludge management system.............................. 67

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LIST OF PLATES

Plate 3.1Orthophotographic map of the case study area .............................................................. 37

Plate 3.2 Screen chamber .............................................................................................................. 39

Plate 3.3 Salasala Faecal sludge pond........................................................................................... 40

Plate 3.7 Depth measurement ....................................................................................................... 43

Plate 3.7: Spectrophotometer ........................................................................................................ 45

Plate 3.5 Laboratory Sample analysis for physical parameter ...................................................... 48

Plate 3.8 Laboratory sample dilution for of chemical parameters analysis .................................. 48

Plate 3.9 Dumped Solid waste from screen .................................................................................. 68

Plate 3.6 Area used for grazing..................................................................................................... 69

Plate 3.7: Faecal sludge disposing activity conducted by worker wears PPE .............................. 70

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|ACRONYMS AND ABBREVIATION

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ACRONYMS AND ABBREVIATION

BOD Biochemical Oxygen Demand

COD Chemical Oxygen Demand

CW Constructed Wetland

FC Faecal Coliforms

FS Faecal Sludge

M+O Maintenance and operation cost

NH3-N Ammonia Nitrogen

NH4-N Ammonium Nitrogen

SS Suspended Solids

TBS Tanzania Bureau of Standards

TDS Total dissolved solids

TKN Total Kjeldahl Nitrogen

TOC Total Organic Carbon

TS Total Solids

TSh Tanzania Shillings

TVS Total Volatile Solids

WHO World Health Organization

WSP Waste Stabilization Ponds

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|CHAPTER ONE

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CHAPTER ONE

1.0 GENERAL INTRODUCTION

In Dar es Salaam, it has been estimated to have a population of about 3.5 million people

of which 70% of the population lives in 40 unplanned settlements. The total number of

households is about 547,000 with an average size of 6.4 persons. Only15% of the

households is connected to the old and degenerated sewerage system which discharges to

the 8 oxidation ponds of which only 4 of the ponds are considered to be operating,

University of Dar-es- Salaam Kurasini Mikocheni and Vingunguti

The sewerage system covers only an area of City Center, parts of Sinza, Ubungo and

Vingunguti. 80% of the households in the rest of Dar es Salaam depends on-site

sanitation facilities such as septic tanks, soak-away pits or pit latrines for wastewater

treatment. With interval of 2-3 years, the faecal sludge of onsite sanitation facilities needs

to be dislodged

Fecal sludge (FS) is defined as the sludge of variable consistency collected from on-site

sanitation systems and is comprised of varying concentrations of settle able or settled

solids (Heinss et al., 1998).

From early, it has been know that, the managing of faecal sludge from local community

is the municipal responsibility, however the current condition and fast expansion of Dar

es salaam metropolitan, has cause the current system of wastewater and faecal sludge

treatment to fail to satisfy the needs. Later, the circumstance has creates opportunity for

local and private entrepreneurs to make money through treatment and disposal of faecal

sludge. Most of private entrepreneurs lack knowledge of proper treatment, handling and

disposal of faecal matter. Uncontrolled and indiscriminate dumping of FS removed from

on-site or other faecal sludge treatment systems creates the potential risks for human

health through human contact with untreated FS and the potential for drinking water

contamination (Van oven, 2004).

Faecal sludge treatment pools a great demand especially in developing countries, there

are different methods used to treat Faecal sludge, each methods has its merits and

demerits.


2

Whereas there are great demands of treating and disposing faecal sludge in sprawling

areas, final application or disposal challenges ascend. The widely and suitable option

used is the land application. The constraints on the land application of sludge vary

according to the treatment to which the sludge has been subjected and the crops which

are produced subsequent to the sludge application. The constraints apply particularly to

conventionally treated sludge’s where there is a greater risk of pathogens being present.

The constraints have to be more stringent the greater the risk to the consumer. For

example there is a much higher risk when fruit and vegetables are eaten raw, as with

salads, than from processed cereals from arable land. In reality, sludge would not be used

on land growing salad crops and this guidance would apply in situations where a farmer

growing, for instance, arable crops fertilized with sludge plans to change the land use to

salad crops without sludge. Evidence to justify the 10-month no-harvest recommendation

for vegetables in ground contact was presented by Carrington et al. (1998)

While the major output of the treatment system is wastewater and bio solids, Wastewater

from treatment system also can presents a source of hazards to public health and

environment. Watercourses when contaminated then utilized by man either as a source of

portable water or for washing or bathing would present potential risk of transmission of

large number of water related diseases (Horan, 1991)

Therefore in order to achieve the goal of public health prevention and environmental

protection, care must be taken while treating faecal sludge as well as wastewater before

disposing to the land or to reuse for agriculture activities.


3

1.1 Justification and Motivation

Dar es Salaam is the metropolitan city with each day increases in population. It has more

than 2,500,000 populations in which large number of population depends on on-site

sanitation facilities such as septic tanks, soak-away pits or pit latrines for wastewater

treatment. In course of time, essentially 2-3 years the systems usually are emptied of

sludge for final treatment and disposal. The Salasala Private Faecal sludge management

systems receives the faecal sludge from on-site sanitation facilities of the whole area of

Tegeta Boko, Bunju, Ununio, Wazo Hill, Salasala, KunduchiMtongani, Kunduchi,

Africana and part of Mikocheni neighborhoods with hesitant from people around the

facility and organization such as NEMC and OSHA about its performance and suitability

in managing and treating faecal sludge. Uncontrolled and indiscriminate dumping of FS

removed from faecal related management systems creates the potential risks for human

health and environment’s as well.

1.2 Research problem

The performance and aptitude of Salasala decentralized faecal sludge management

system located at Tegeta Kinondoni Dar es salaam, in polishing Septic tank and pit

latrine as a pre-treated domestic wastewater basically from Tegeta, Boko, Bunju and

Kunduchi neighborhoods has been one of the big issue among the people and

organizations such as NEMC and OSHA. The grievances here are “If the system is

suitable for management of faecal sludge hauled from septic tank and pit latrine though

private cesspit emptier, and also, if the effluent comply with the required standards, i.e.

TBS and WHO for treating domestic wastewater to meet irrigation purpose which is the

current activity performed by the treatment owner with plant final effluent. Disposing of

untreated or partial treated wastewater to the Environment, threaten and cause damage to

Public health and Environments, especially if it does not comply with the required

standards.


4

1.3 Objective of the Study

The general objective of this study was to assess Salasala privately operated decentralized

Faecal sludge management system and critical analyze the improvements which are

needed to make it suitable (cost effective) faecal sludge management system with a

potential for citywide adoption

1.3.1 Specific objectives

The specific objectives of this study were the following:

Technical assessment of Salasala private operated decentralized faecal sludge

management system,

Assessment of aesthetic and land scape quality of Salasala private operated

decentralized faecal sludge management system,

Economic assessment of Salasala private operated decentralized faecal sludge

management system,

Analysis of the improvements needed to make the Salasala decentralized system a

suitable faecal sludge management system,

1.4 Scope

This study is limited to assess the performance of existing private decentralized faecal

sludge management system located at, Tegeta-Dar es salaam and offer improvements

which are needed to make it suitable faecal sludge management system with a potential

for citywide adoption

1.5 Expected output

The expected output involves a well writer report with the critical improvements needed

to make Salasala private decentralized faecal sludge management system suitable faecal

sludge management system with a potential for citywide adoption.

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|CHAPTER TWO

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CHAPTER TWO

LITERATURE REVIEW

2.1 Fecal Sludge

Faecal sludge is defined by as Sludges of variable consistency collected from on-site

sanitation systems, such as latrines, non-sewered public toilets, septic tanks and aqua

privies (Heinss et al. (1998). The faecal sludge comprises varying concentrations of

settable or settled faecal solids as well as of other, non faecal matter.

Fecal Sludge is a highly variable, organic material with considerable levels of grease,

grit, hair, and debris. In addition to its variable nature, FS tends to foam upon agitation,

resists settling and dewatering and serves as a host for many disease-causing viruses,

bacteria, and parasites (USEPA, 1999).

The helminthes eggs, ammonium, and organic and solids concentrations in fecal sludge

are typically higher by a factor of ten or more than in wastewater (Montangero and

Strauss, 2002).The criteria and procedures for the treatment of fecal sludge’s, therefore,

differ from those used for domestic wastewater. As fecal sludge contains a variety of

fertilizers, including nitrogen and phosphorus and is low in chemical contaminants, it

tends to lend itself well to agricultural use. Prior to disposal of fecal sludge or land

application for agricultural use, however, it must be stabilized to reduce levels of

pathogenic organisms, lower the potential for putrefaction, and reduce odors (CWRS,

1999).

2.1.1 Sewage sludge

Common value for sewage sludge is a solids content of around 2%. Anaerobically

digested sludge generally has higher solids content, while aerobic sludge has lower solids

content (De Maeseneer, 1997). In general, the nutrient concentrations of sewage sludge

are lower than in human excreta and faecal sludge


6

2.1.2 Faecal sludge characteristics

The physical characteristics of fecal sludge (FS) vary significantly due, among other

factors, to climate, tank emptying technology and pattern, storage duration (months to

years), performance of tank, additional components of FS including grease, kitchen/solid

waste, and potential groundwater intrusion (Montangero and Strauss, 2002).Compared to

sludge’s from wastewater treatment plants or to municipal wastewaters characteristics

differ widely according to location (from household to household, from city district to

city district, from city to city).The factor’s influencing faecal sludge characteristics are

illustrated in Figure 2.1

Figure 2.1: Factors influencing FS characteristics. (Source: Heinss et al., 1998)

General Characteristics of faecal sludge characteristics are given by SANDEC (1997)

(Table 2.1).Concentrations of COD, ammonium, SS and helminth eggs in FS are much

higher than in sewage due to the lower water contents.


7

Public toilet

sludge

Septage Sewage

Characterization Highly

concentrated,

mostly fresh FS;

stored for days or

weeks only

FS of low

concentration;

usually stored for

several years

;more stabilized

than public toilet

sludge

Sewage for

comparison

Tropical sewage

COD (mg/l) 20-50000 < 10000 500--2,500

COD/BOD 2:1-5:1 5:110:1 2:1

NH4-N (mg/l) 2,-5000 < 1000

TS ≥ 3.5% < 3% 30 - 70

SS (mg/l) ≥ 30,000 = 7000 < 1%

Helminth eggs

(no/litre)

20,-6000 = 4000 200 - 700

Table 2.1: Characteristics of faecal sludge’s (source: Heinss et al., 1998)

2.1.3 Nutrients in sludge

Table 2.2 contains relevant characteristics and per capita quantities of human excreta,

including its resource elements, viz. organic matter, along with phosphorus, nitrogen and

potassium as major plant nutrients. Average nutrient contents of plant matter and cattle

manure are also included for comparison’s sake. Faecal Sludges, if adequately stored or

treated otherwise, may be used in agriculture as soil conditioner to restore or maintain the

humus layer or as fertilizer.


8

Faces Urine Excreta

Quality and consistence

Gram/cap. Day (wet) 250 1200 1450

Gram/cap. Day (dry) 50 60 110

Including 0.35 litres

for anal cleansing

gram/ cap. Day (wet)

1800

m3/cap.year (upon

storage and digestion

for>1 year in pits or

vault in hot climate

0.04-0.07

Water content % 50-95

Chemical

composition

% of dry solids

Organic matter 92 75 83

C 48 13 29

N 4-7 14-18 9-12

P 2 O5 4 3.7 2.7

K20 1.6 3.7 2.7

For comparison

sake

% of dry solids

N P 2 O5 K20

Human excreta 9-12 3.8 2.7

Plant matter 1-11 0.5-2.8 1.1-11

Pig manure 4-6 3-4 2.5-3

Cow manure 2.5 1.8 1.4

Table 2.2 Human excreta per capita quantities and their resource value (Strauss 1985)


9

2.2 Domestic wastewater

Domestic wastewater is the water that has been used by a community and which contains

all the materials added to the water during its use. It is thus composed of human body

wastes (faeces and urine) together with the water used for flushing toilets, and sullage,

which is the wastewater resulting from personal washing, laundry, food preparation and

the cleaning of kitchen utensils. The typical composition of domestic wastewater is

presented in table 2.3 bellow.

Content(all in mg/l exceptsettle able solids)

Weak Medium Strong

Alkalinity 50 100 200

Ammonia (free) 10 25 50

BOD5 (as O2) 100 200 300

Chloride 30 50 100

COD (as O2) 250 500 1000

Total suspendedsolids (TSS)

120 210 400

Volatile (VSS) 95 160 315

Fixed 25 50 85

Settle able solidsml/L

5 10 20

Sulfates 20 30 50

Total dissolvedsolids (TDS)

200 500 1000

Total Kjeldahlnitrogen (TKN) (asN)

20 40 80

Toatal organiccarbon (TOC) (asC)

75 150 300

TotalPhosphorus(as P)

5 10 20

Table 2.3 Typical composition of untreated domestic wastewater (Metcalf and eddy2003)


10

Fresh wastewater is a grey turbid liquid that has an earthy but inoffensive odor. It

contains large floating and suspended solids (such as faeces, rags, plastic containers, and

maize cobs), smaller suspended solids (such as partially disintegrated faeces, paper, and

vegetable peel) and very small solids in colloidal (ie non-settleable) suspension, as well

as pollutants in true solution. It is objectionable in appearance and hazardous in content,

mainly because of the number of disease-causing (‘pathogenic’) organisms it contains. In

warm climates wastewater can soon lose its content of dissolved oxygen and so become

‘stale’ or ‘septic’. Septic wastewater has an offensive odor, usually of hydrogen sulphide.

The composition of human faces and urine is given in Table 2.4. The organic fraction of

both is composed principally of proteins, carbohydrates and fats. These compounds,

particularly the first two, form an excellent diet for bacteria, the microscopic organisms

whose voracious appetite for food is exploited by public health engineers in the

microbiological treatment of wastewater. In addition to these chemical compounds, faces

and, to a lesser extent, urine contains many millions of intestinal bacteria and smaller

numbers of other organisms. The majority of these are harmless – indeed some are

beneficial– but an important minority is able to cause human disease. Sullage contributes

a wide variety of chemicals: detergents, soaps, fats and greases of various kinds,

pesticides, anything in fact that goes down the kitchen sink, and this may include such

diverse items as sour milk, vegetable peelings, tea leaves, soil particles (arising from the

preparation of vegetables) and sand (used to clean cooking utensils).


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Quantities Faces urine

Quantity (wet) per personper day

135–270 g 1.0-1.3kg

Quantity (dry solids) perperson per day

35–70 g 50-70g

Approximate composition (%)Moisture 66–80 44–55 4.5Organic matter 88–97 15-19Nitrogen 5.0–7.0 2.5-5.0Phosphorus (as P 2 O5) 1.0–2.5 3.0-4.5Carbon 44–55 11–17Calcium (as CaO) 4.5 4.5–6.0

Table 2.4 Composition of human faeces and urine (Source: Gotaas 1956)

2.2.1 Domestic waste Water Characteristics

Wastewater is mainly comprised of water (99.9%) together with relatively small

concentrations of suspended and dissolved organic and inorganic solids which are highly

hazardous in nature and may cause pollution of stream, underground water and lakes. So

it is important to know the characteristics of wastewater which will give the idea of

degree pollution and method of treatment to be adopted for safe disposal. These

characteristics are divided into three classes i.e. physical, chemical and biological.

(Chatterjee, 1973)

2.2.1.1 Physical Characteristics

i. Temperature

The temperature of wastewater is usually higher because of the addition of warm water

from domestic use. Wastewater temperature is important for two reasons.

Biological processes are temperature dependent and

Chemical reactions and reaction rates and aquatic life are all temperature

sensitive.

The best temperatures for wastewater treatment range from 15o C to 45o C


12

ii. Solids

Solid materials in wastewater can consist of organic and/or inorganic materials

and organisms. The solids must be significantly reduced by treatment otherwise

they can increase BOD levels when discharged to receiving waters. Solids are

classified as;

Total solids

Suspended solids

Dissolved solids

Settable solids

Fixed solids

2.2.1.2 Chemical characteristics

i. Inorganic

Inorganic minerals, metals, and compounds, such as sodium, potassium, calcium,

phosphorus, nitrogen, magnesium, cadmium, copper, lead, nickel, and zinc are

common in domestic wastewater. Phosphorus and nitrogen are the most

environmental significant elements in wastewater for causing eutrophication. Most

of these inorganic substances are relatively stable and cannot be broken down easily

by organisms in wastewater.

ii. Phosphorus

Phosphorus exists in wastewater in many forms and includes soluble

orthophosphate ion (PO4-3), organically-bound phosphate, and other

phosphorus/oxygen forms, calcium phosphate.

Effects of Phosphorous and Nitrogen (Nutrients)

Increases algal photosynthesis (eutrophication) i.e. increased plant life on

surface, Reduces light in lower levels.

Organic nitrogen and ammonia are converted to nitrates in water

Nitrates are converted to nitrites in digestive system


13

Nitrites are assimilated into blood stream where they are converted by

respired oxygen to nitrates

May cause suffocation (blue baby syndrome)

iii. Oil and grease

Oil and grease is the term given to the combination of fats, oils, waxes, and other related

constituents found in wastewater. When large amounts of oils and greases are discharged to

receiving waters from community systems they increase BOD level.

iv. pH

The pH is the measure of the inverse concentration of hydrogen ions. The acidity or alkalinity of

wastewater affects both treatment and the environment.

v. Organic matter

Organic materials in wastewater originate from plants, animals, or synthetic organic

compounds, and may enter in wastewater through human wastes, paper products, detergents,

cosmetics, foods, and from agricultural, commercial, and industrial sources.

vi. BOD – biochemical oxygen demand

The BOD test measures the amounts of dissolved oxygen which is consumed by microorganisms

in decomposing organic matter.

Effect of BOD

Depletes dissolved oxygen from streams, lakes and oceans

May cause death of aquatic organisms

Increases anoxicity in receiving water bodies


14

vii. Gases

Methane, Hydrogen sulfide, Carbon dioxide and ammonia are common gases emitted from waste

water. These gases are toxic and can cause odors. Ammonia as a dissolved gas in wastewater is

dangerous to aquatic life beyond acceptable levels

2.2.1.3 Biological characteristics

Pathogens

Possible pathogens likely to be found in wastewater include viruses, parasites, and bacteria. Total

Coliforms and Fecal Coliforms are indicators of pathogens and level of biological pollution in

wastewater

2.3 Faecal Sludge Treatment

Unlike digested sludge produced in mechanized biological wastewater treatment facilities or in

other types of wastewater treatment works (e.g. waste stabilization ponds, oxidation ditches), the

organic stability of FS attains varying levels. This variability is due to the fact that the anaerobic

degradation process, which takes place in onsite sanitation systems, depends on several factors

like ambient temperature, retention period and the presence of inhibiting substances. As the

faecal matter is not being mixed or stirred, this impairs the degradation process (Koottatep et al.,

2003). The choice of a FS treatment option depends primarily on the characteristics of the FS

generated in a particular town or cities, budget availability, land availability and the treatment

objectives (Montangero and Strauss, 2004). The widely varying quality and quantity of FS

requires a careful selection of appropriate treatment options Primary treatment may encompass

solids liquid separation or biochemical stabilization if the

FS is still fresh but has undergone partial degradation during on-plot storage and prior to

collection.


15

Figure 2.2 Overview of the modest faecal treatment options ( Montangero & Strauss 2004)

2.3.1 Solids/liquid separation

Dewatering or the separation of the solids and liquids of the sludge is primarily meant to reduce

the volume of the sludge and to increase the dry matter content. Most of the processes described

in this paragraph are normally used for the treatment of (primary and secondary) sewage sludge,

except the composting and vermi-composting processes which are also used for treatment or

handling of other organic wastes.

2.3.2 Gravity solids/liquid separation

Gravity dewatering makes use of sedimentation. Also, evaporation processes increased by wind

and solar energy contribute to the reduction of the water content of the sludge.

2.3.2.1 Sedimentation tanks

Using lagoons or sedimentation basins for sewage sludge dewatering a TS contents of 10 -35%

and a volume reduction of 40 - 50% (and even more when one starts with a solids content of 2 -

5 %) can be achieved (NVA, 1994; Strauss, 1999). In sedimentation tanks sedimentation and


16

flotation of solid material separate the water and sludge. Heinss et al. (1997) reported about a FS

sedimentation/thickening basin, in which a thickening concentration TS = 15% could be attained.

2.3.2.2 Drying beds without plants

Gravity dewatering can also take place in (unplanted) drying beds. Similar to lagoons, drying

beds also require much space. Dewatering is attained both by evaporation and seepage.

According to Heinss et al. (1997) 40 - 70% TS content in the dewatered faecal sludge may be

attained within 8-12 days, with loading rates of 100 - 200 kg TS/m2·yr. These loading rates are

considerably lower than, for example, the loading rates that can be applied in sedimentation

tanks, which results in a larger area per capita (0,05 m2/cap). However, the effluent of drying

beds needs less polishing than the effluent of sedimentation tanks.

Based on a questionnaire and visits to wastewater treatment plants in the USA, Kim and Smith

(1997) reported that the type of sludge influences the loading rates that can be applied on sand-

drying beds without plants. Using different drying bed criteria, the solid loading rates for open

sand-drying bed range from 64 to 113 kg/m2·yr. For anaerobic sludge, the EPA recommended

100 to 160 kg/m2·yr. as sand drying bed design criteria. These conventional unplanted sand-

drying beds are simple to operate and maintain, and are inexpensive to build. Some

disadvantages are, however, that dewatering can take 2 to 4 weeks (depending on the climate,

soil type etc.), the removal of the dried sludge requires intensive labor and there is always the

danger of clogging or low dewater ability potential with undigested or only partly dewatered

Sludges.

2.3.3 Mechanical solids/liquid separation

Mechanical dewatering methods have low area requirement and the TS content of the solid

fraction can be controlled precisely. Mechanical methods are characterized by high capital costs,

high-energy consumption (1 - 10 kWh/m3) (STORA, 1981) and the need for adding chemicals

for conditioning. Most common processes applied are:

Vacuum filtering

Filter pressing

(Chemical added) centrifuging

Belt filter pressing


17

The TS content that can be achieved by mechanical dewatering processes is comparable with

natural dewatering processes: 15 - 45% (NVA, 1994).

2.3.4 Digestion

The digestion of faecal sludge is not primarily meant for solid / liquid separation. During the

digestion process the organic material is decomposed. The biogas produced during the process

can be collected and used for cooking or heating, while the effluent of the digesters can be used

for plant fertilization and soil amendment purposes. The sludge that remains in the digester has

to be removed and usually needs some further treatment e.g. drying, composting, land

application or incineration. Zhao Xihui reports about four different types of digesters that are

used in China for night soil treatment (Xihui, 1988). These digesters can achieve a high parasitic

ova reduction: > 93%.The effluent of the digesters needs a post treatment before discharging into

surface water or sewer systems. The application of biogas digesters resulted in a reduced

prevalence of infectious diseases and also the density of flies decreased remarkably. In

Guatemala dome-shaped Chinese type digesters have been tested. Latrines fed the digesters. The

experiments made clear that the low temperatures and the low air pressure had a negative effect

on the treatment process. The underground-type Chinese digester used as a latrine produced

biogas, solids and a relatively clear effluent. The solids and effluent can be used as fertilizer as

the effluent contains high concentrations of nitrogen, phosphorus and potassium. The pathogen

concentration in the effluent was acceptable for reuse in agriculture and fishponds (Estrada et al.,

1986).

2.3.5 Anaerobic Decomposition

In order to achieve anaerobic decomposition, molecular oxygen and nitrate must not be present

as terminal electron acceptors. Sulfate (S4O2), carbon dioxide, and organic compounds that can

be reduced serve as terminal electron acceptors. The reduction of sulfate results in the production

of equally odoriferous organic sulfur compounds called mercaptans and hydrogen sulfide (H2 S).

The anaerobic decomposition (fermentation) of organic matter generally is considered to be a

three-step process. In the first step, waste components are hydrolyzed. In the second step,

complex organic compounds are fermented to low molecular weight fatty acids (volatile acids)

.In the third step, the organic acids is converted to methane. Carbon dioxide serves as the

electron acceptor.


18

Anaerobic decomposition yields carbon dioxide, methane, and water as the major end products.

Additional end products include ammonia, hydrogen sulfide, and mercaptans. As a consequence

of these last three compounds, anaerobic decomposition is characterized by highly objectionable

odors.

Because only small amounts of energy are released during anaerobic oxidation, the amount of

cell production is low. Thus, sludge production is low. This fact is used in wastewater treatment

to stabilize and reduce the volume of Sludges produced during aerobic and anoxic

decomposition.

Typically, direct anaerobic decomposition of wastewater is not used for dilute municipal

wastewater. The optimum growth temperature for the anaerobic bacteria is at the upper end of

the mesophilic range. Thus, to get reasonable biodegradation, the temperature of the culture must

be elevated. For dilute wastewater, this is not practical. For concentrated wastes (BOD greater

than1, 000 mg/L) and sludge treatment, anaerobic digestion is quite appropriate.

2.4 Wetlands and sludge treatment

Wetlands are parts of the earth’s surface between true terrestrial and aquatic systems. Thus

shallow lakes, marshes, swamps, bogs, dead riverbeds, borrow pits, are all wetlands irrespective

of their extent and degree of human interventions. Wetlands are generally shallow and thus

differentiated from deep water bodies. Wetlands often include three main components. These are

the presence of water, unique soils differing from those of uplands and presence of vegetation

adapted to wet conditions. Gosh (1995)

2.4.1 Natural wetland

Natural wetlands are in many developing countries in use for the treatment of domestic and even

industrial wastewater. In Tanzania, natural wetlands occupy over 7% of the country's surface

area. Most natural wetland takes the form of swamps with macrophytes vegetation typical to

such areas including reeds, bulrushes, cattails, and sedges. Some wetlands are naturally seasonal

in nature and the controlled discharge of effluent from WSP or constructed wetlands can both

maintain the natural swam through the dry season and allow it to polish the effluent before this

reaches the watercourse. Compared to other wastewater treatment technologies they are a cheap


19

and appropriate solution against water pollution. However, the controlled use of natural wetlands

for water pollution may become a problem, especially when the wetlands are used for other

purposes, for example as a clean water source. So the use of natural wetlands for wastewater

treatment may conflict with important issues as wetland bio-diversity and the sustainable

development of natural resources (Denny, 1997). Constructed wetlands may be more

controllable alternatives, which are appropriate and may be cost-effective solutions.

2.4.2 Constructed wetland

Constructed Wetlands (CW) is a biological wastewater treatment technology designed to mimic

processes found in natural wetland ecosystems. These systems use wetland plants, soils and their

associated microorganisms to remove contaminants from wastewater. Application of constructed

wetlands for the treatment of municipal, industrial and agricultural wastewater as well as storm

water started in the 1950s and they have been used in different configurations, scales and

designs. CWs are receiving increasing worldwide attention for wastewater treatment and

recycling due to the following major advantages:

Use of natural processes

Simple and relatively inexpensive to construct (can be constructed with local materials)

Simple operation and easy to maintain

Cost-effectiveness (low construction and operation costs)

Process stability i.e. relatively tolerant of fluctuating hydrologic and contaminant loading

rates

Provide effective and reliable wastewater treatment

Provide indirect benefits such as green space, wildlife habitats and recreational and

educational areas.

Research studies have shown that wetland systems have great potential in controlling water

pollution from domestic, industrial and non-point source contaminants. As it has been widely

recognized as a simple, effective, reliable and economical technology compared to several other

conventional systems, it can be a useful technology for wastewater treatment. However CWs has

the following disadvantages


20

The land requirements (cost and availability of suitable land)

Current imprecise design and operation criteria

Biological and hydrological complexity and our lack of understanding of important

process dynamics.

The costs of gravel or other fills, and site grading during the construction period.

Possible problems with pests. Mosquitoes and other pests could be a problem for an

improperly designed and managed SSF. The system may be used for small communities

and, therefore, may be located close to the users. The dependence of wetland community

on hydrologic patterns is most obvious in the change in species composition resulting

from alterations in water depths and flows.

There are various types of constructed wetland systems for treating wastewater based on the type

of plants used, type of media used and flow dynamics.

2.4.2.1 Types of Constructed Wetlands

Constructed wetlands for wastewater treatment can be categorized as either Free Water Surface

(FWS) or Subsurface Flow (SSF) systems. In FWS systems, the flow of water is above the

ground, and plants are rooted in the sediment layer at the base of water column (Figure 2.3) In

SSF systems, water flows through a porous media such as gravels or aggregates, in which the

plants are, rooted (Figure 2.4). Table2.5 illustrates the type of wetlands, vegetation types and

water column contacts in constructed wetlands.

Figure 2.3: Emergent macrophytes treatment system with surface flow


21

Figure 2.4: Emergent macrophytes treatment system with horizontal sub surface flow

Constructed wetland type Type of vegetation Section in contact with water

column

Free water surface (FWS) Emergent Stem, limited leaf contact

Floating Root zone, some stem tubers

Submerged Photosynthetic part, possibly root zone

Sub-surface flow (SSF) Emergent Rhizome and root zone

Table 2.5 Vegetation type and water column contact in constructed wetlands

SSF systems are most appropriate for treating primary wastewater, because there is no direct

contact between the water column and the atmosphere. There is no opportunity for vermin to

breed, and the system is safer from a public health perspective. The system is particularly useful

for treating septic tank effluent or grey water, landfill leachate and other wastes that require

removal of high concentrations organic materials, suspended solids, nitrate, pathogens and other

pollutants. The environment within the SSF bed is mostly either anoxic or anaerobic Oxygen is

supplied by the roots of the emergent plants and is used up in the Biofilm growing directly on the

roots and rhizomes, being unlikely to penetrate very far into the water column itself. SSF


22

systems are good for nitrate removal (denitrification), but not for ammonia oxidation

(nitrification), since oxygen availability is the limiting step in nitrification.

Constructed wetlands remove pollutants from wastewater through various physical, chemical and

biological mechanisms. Some of the main pollutant removal mechanisms in constructed wetlands

are presented in table 2.6 below:

Wastewater characteristics Removal mechanism

Suspended solids Sedimentation

Filtration

Soluble organics Aerobic microbial degradation

Anaerobic microbial degradation

Phosphorous Matrix sorption

Plant uptake

Nitrogen Ammonification followed by microbial

nitrification

Denitrification

Plant uptake,

Matrix adsorption

Ammonia volatilisation (mostly in SF system)

Metals Adsorption and cation exchange

Complexation

Precipitation

Plant uptake

Microbial oxidation/reduction

Pathogens Sedimentation

Filtration

Natural die-off

Predation

UV irradiation (SF system)

Excretion of antibiotics from roots of macrophytes

Table 2.6 Pollutant removal mechanisms in constructed wetlands (source: cooper et al., 1996)


23

2.4.2.2 Configuration, Zones and components of constructed wetlands

Influents to constructed wetland can range from raw wastewater to secondary effluents. Most

constructed wetlands have the following zones: inlet zone, macrophytes zone, and littoral zone

and outlet zones. The components associated in each zones are as shown in Table 2.7 and can

include substrates with various rates of hydraulic conductivity, plants, a water column,

invertebrate and vertebrates, and an aerobic and anaerobic microbial population. The water flow

is maintained approximately 15 – 30 cm below the bed surface. Plants in wastewater systems

have been viewed as nutrient storage compartments where nutrient uptake is related to plant

growth and production. Harvesting before senescence may permanently remove nutrients from

the systems. Within the water column, the stems and roots of wetland plants significantly provide

the surface area for the attachment of microbial population. Wetland plants have the ability to

transport atmospheric oxygen and other gases down into the root to the water column. Most

media used include crushed stones, gravels, and different soils, either alone or in combination.

Most beds are underlain by impermeable materials to prevent water seepage and assure water

level control. Wastewater flows laterally, being purified during contact with media surface and

vegetation roots. The sub-surface zone is saturated and generally anaerobic, although excess DO

conveyed through the plant root system supports aerobic microsites adjacent to the root and

rhizomes.

Zones Components Functions

Inlet zone Inlet structure, splitter box

Flow distribution across the full width at a

minimum of 3 – 5 m interval

Macrophyte zone

Porous bed/substrate, open

water, vegetation, island,

mixing baffles, flow diversion

To provide the substrate with high hydraulic

conductivity; to provide surface for the

growth of Biofilm; to aid in the removal of

fine particles by sedimentation or filtration; to

provide suitable support for the development

of extensive root and rhizome system for

emergent plants.

Reduce short circuiting by re-orienting flow

path; reduce stagnant areas by allowing for

mixing by wind; enable UV disinfections of


24

Deep water zone Usually deeper, non-vegetated bacteria and other pathogens; provide habitat

for waterfowl.

Littoral zone Littoral area

Littoral vegetation protects embankment from

erosion; littoral vegetation serves to break up

wave action.

Outlet zone Collection devices, spillway,

weir, outlet structures

Control the depth of the water in the wetland;

collect the effluent water without creating of

dead zones in the wetlands; provide access for

sampling and flow monitoring.

Table 2.7 Wetland zones and their associated components

2.4.2.3 Processes in Sub-surface Flow Constructed Wetlands (SSFCW)

Wetland can effectively remove or convert large quantities of pollutants from point sources

(municipal, industrial and agricultural wastewater) and non-point sources (mines, agriculture and

urban runoff), including organic matter, suspended solids, metals and nutrients. The focus on

wastewater treatment by constructed wetlands is to optimize the contact of microbial species

with substrate, the final objective being the bioconversion to carbon dioxide, biomass and water.

Wetlands are characterized by a range of properties that make them attractive for managing

pollutants in water. These properties include high plant productivity, large adsorptive capacity of

the sediments, high rates of oxidation by micro flora associated with plant biomass, and a large

buffering capacity for nutrients and pollutants (Cooper, 1990). Table 2.8 provides an overview of

pollutant removal mechanisms in constructed wetlands.

Pollutant Removal Processes

Organic material (measured as BOD) Biological degradation, sedimentation,

microbial uptake

Organic contaminants (e.g., pesticides) Adsorption, volatilization, photolysis, and

biotic/abiotic degradation

Suspended solids Sedimentation, filtration

Nitrogen Sedimentation, nitrification/denitrification,


25

microbial uptake, volatilization

Phosphorous Sedimentation, filtration, adsorption, plant and

microbial uptake

Pathogens Natural die-off, sedimentation, filtration,

predation, UV degradation, adsorption

Heavy metals Sedimentation, adsorption, plant uptake

Table 2.8: Overview of pollutant removal mechanisms

2.4.2.4 Horizontal surface Flow Constructed Wetland (SFCW)

A Horizontal surface Flow Constructed Wetland is large gravel and sand-filled channel that is

planted with aquatic vegetation. As wastewater flows horizontally through the channel, the filter

material filters out particles and microorganisms degrade organics.

The water level in a Horizontal surface Flow Constructed Wetland is maintained at 5 to 15cm

below the surface to ensure subsurface flow. The bed should be wide and shallow so that the

flow path of the water is maximized (figure 2.5). A wide inlet zone should be used to evenly

distribute the flow. Pre-treatment is essential to prevent clogging and ensure efficient treatment.

Figure 2.5: Section through Horizontal surface Flow Constructed Wetland


26

The bed should be lined with an impermeable liner (clay or geotextile) to prevent leaching.

Small, round, evenly sized gravel (3–32mm in diameter) is most commonly used to fill the bed to

a depth of 0.5 to 1m. To limit clogging, the gravel should be clean and free of fines. Sand is also

acceptable, but is more prone to clogging. In recent years, alternative filter materials such as PET

have been successfully used.

The removal efficiency of the wetland is a function of the surface area (length multiplied by

width), while the cross-sectional area (width multiplied by depth) determines the maximum

possible flow. A well-designed inlet that allows for even distribution is important to prevent

short-circuiting. The outlet should be variable so that the water surface can be adjusted to

optimize treatment performance.

The filter media acts as both a filter for removing solids, a fixed surface upon which bacteria can

attach, and a base for the vegetation. Although facultative and anaerobic bacteria degrade most

organics, the vegetation transfers a small amount of oxygen to the root zone so that aerobic

bacteria can colonize the area and degrade organics as well. The plant roots play an important

role in maintaining the permeability of the filter.

Any plant with deep, wide roots that can grow in the wet, nutrient-rich environment is

appropriate.

2.4.2.4.1 Adequacy of surface flow constructed wetlands

Clogging is a common problem and therefore the influent should be well settled with primary

treatment before flowing into the wetland. This technology is not appropriate for untreated

domestic waste water (i.e. blackwater). This is a good treatment for communities that have

primary treatment (e.g. Septic Tanks or WSPs) but are looking to achieve a higher quality

effluent. This is a good option where land is cheap and available, although the wetland will

require maintenance for the duration of its life.

Depending on the volume of water, and therefore the size, this type of wetland can be

appropriate for small sections of urban areas, peri-urban and rural communities. They can also be

designed for single households.

Horizontal Subsurface Flow Constructed Wetlands are best suited for warm climates but they

can be designed to tolerate some freezing and periods of low biological activity.


27

2.4.2.4.2 Health Aspects/Acceptance

The risk of mosquito breeding is reduced since there is no standing water compared to the risk

associated with Free-Water Surface Constructed Wetlands. The wetland is aesthetically pleasing

and can be integrated into wild areas or parklands.

2.4.2.4.3 Maintenance of surface flow constructed wetlands

With time, the gravel will clog with accumulated solids and bacterial film. The filter material

will require replacement every 8 to 15 or more years. Maintenance activities should focus on

ensuring that primary treatment is effective at reducing the concentration of solids in the

wastewater before it enters the wetland. Maintenance should also ensure that trees do not grow in

the area as the roots can harm the liner.

2.5 Biological processes in CWs

There are six major biological reactions involved in the performance of constructed wetlands,

including photosynthesis, respiration, fermentation, nitrification, denitrification and microbial

phosphorus removal (Cooper, 1990). Photosynthesis is performed by wetland plants and algae,

with the process adding carbon and oxygen to the wetland. Both carbon and oxygen drive the

nitrification process. Plants transfer oxygen to their roots, where it passes to the root zones

(rhizosphere). Respiration is the oxidation of organic carbon, and is performed by all living

organisms, leading to the formation of carbon dioxide and water. The common microorganisms

in the CW are bacteria, fungi, algae and protozoa. The maintenance of optimal conditions in the

system is required for the proper functioning of wetland organisms. Fermentation is the

decomposition of organic carbon in the absence of oxygen, producing energy-rich compounds

(e.g., methane, alcohol, volatile fatty acids). This process is often undertaken by microbial

activity. Nitrogen removal by nitrification/denitrification is the process mediated by

microorganisms. The physical process of volatilization also is important in nitrogen removal.

Plants take up the dissolved nutrients and other pollutants from the water, using them to produce

additional plant biomass.


28

2.6 Chemical processes

Metals can precipitate from the water column as insoluble compounds. Exposure to light and

atmospheric gases can break down organic pesticides, or kill disease-producing organisms (EPA,

1995). The pH of water and soils in wetlands exerts a strong influence on the direction of many

reactions and processes, including biological transformation, partitioning of ionized and un-

ionized forms of acids and bases, cation exchange, solid and gases solubility.

2.7 Physical processes

Sedimentation and filtration are the main physical processes leading to the removal of

wastewater pollutants. The effectiveness of all processes (biological, chemical, physical) varies

with the water residence time (i.e., the length of time the water stays in the wetland). Longer

retention times accelerate the remove of more contaminants, although too-long retention times

can have detrimental effects.

2.8 Process rates

The chemical and biological processes occur at a rate dependent on environmental factors,

including temperature, oxygen and pH. Metabolic activities are decreased by low temperature,

reducing the effectiveness of pollutant uptake processes relying on biological activity. Low

oxygen concentrations limit the processes involving aerobic respiration within the water column,

and may enhance anaerobic processes, which can cause further degradation of water quality.

Many metabolic activities are pH-dependent, being less effective if the pH is too high or low.

2.9 Hydrological limitations

The capacity of wetlands to treat wastewater is limited, both in terms of the quantity of water,

and the total quantity of the pollutants. Hydraulic overloading occurs when the water flow

exceeds the design capacity, causing a reduction in water retention time that affects the rate of

pollutant removal. Pollutant overloading occurs when the pollutant input exceeds the process

removal rates within the wetland (Metacalf., 1991). Hydraulic overloading may be compensated

for by using surcharge mechanisms, or the design may be based on a flush principle, whereby

large water flows bypass the wetland when used for storm water treatment Mashauri, 1993).


29

Inflow variations are typically less extreme for wetlands treating municipal wastewaters, with

incoming pollutant loads also being more defined and uniform.

2.10 Wetland nitrogen processes

The most important nitrogen species in wetlands are dissolved ammonia (NH+

4), nitrite (NO

-

2),

and nitrate (NO-

3). Other forms include nitrous oxide gas (N

2O), nitrogen gas (N

2), urea

(organic), amino acids and amine (Kadlec & Knight, 1996). Total nitrogen in any system is

referred to as the sum of organic nitrogen, ammonia, nitrate and nitrous gas (Organic-N + NH+

4+

NO-

3+ N

2O). The various nitrogen forms are continually involved in transformations from

inorganic to organic compounds, and vice-versa.

NH+

4,+ O

2

+NitrosomonasH

++ NO

-

2+ H

2O

The nitrite produced is oxidized aerobically by nitrobacteria bacteria, forming nitrate as follows:

NO-

2+ O

2

NitrobacterNO

-

3

The first reaction produces hydroxonium ions (acid pH), which react with natural carbonate to

decrease the alkalinity (Metcalf, 1991). In order to perform nitrification, the nitrosomonas must

compete with heterotrophic bacteria for oxygen. The BOD of the water must be less than 20 mg/l

before significant nitrification can occur (Reed et al., 1995). Temperatures and water retention

times also may affect the rate of nitrification in the wetland. Denitrification is the process in

which nitrate is reduced in anaerobic conditions by the benthos to a gaseous form. The reaction

is catalyzed by the denitrifying bacteria Pseudomonas spp. and other bacteria, as follows:

NO-

3+ Organic-C

Denitrifying BacteriaN

2(NO &N

2O)

(G)+ CO

2(G)+ H

2O (3.4)

Denitrification requires nitrate, anoxic conditions and carbon sources (readily biodegradable).

Nitrification must precede denitrification, since nitrate is one of the prerequisites. The process of

denitrification is slower under acidic condition. At a pH between 5-6, N20 is produced. For a pH


30

below 5, N2

is the main nitrogenous product (Nuttall et al., 1995). NH+

4is the dominant form of

ammonia-nitrogen at a pH of 7, while NH3

(present as a dissolved gas) predominates at a pH of

12. Nitrogen cycling within, and removal from, the wetlands generally involves both the

translocation and transformation of nitrogen in the wetlands, including sedimentation

(resuspension), diffusion of the dissolved form, litter fall, adsorption/desorption of soluble

nitrogen to soil particles, organism migration, assimilation by wetland biota, seed release,

ammonification (mineralisation) (Orga-N – NH+

4), ammonia volatilization (NH

+

4– NH

3(gas)),

bacterially-mediated nitrification/denitrification reactions, nitrogen fixation (N2, N

2O (gases –

organic-N)), and nitrogen assimilation by wetland biota (NH+

4, Nox organic – N, with NO

x

usually as NO-

3). Precipitation is not a significant process due to the high solubility of nitrogen,

even in inorganic form. Organic nitrogen comprises a significant fraction of wetland biota,

detritus, soils, sediments and dissolved solids (Kadlec , 1996).

2.11 Wetland in Phosphorus removal

Phosphorus is an essential requirement for biological growth. An excess of phosphorus can have

secondary effects by triggering eutrophication within a wetland, and leading to algal blooms and

other water quality problems. Phosphorus may enter a wetland in dissolved and particulate

forms. It exits wetlands in outflows, by leaching into the sub-soil, and by removal by plant and

animals. Phosphorus removal in wetlands is based on the phosphorous cycle, and can

Involve a number of processes. Primary phosphorus removal mechanisms include adsorption,

filtration and sedimentation. Other processes include complexation/precipitation and

assimilation/uptake. Particulate phosphorus is removed by sedimentation, along with suspended

solids. The configuration of constructed wetlands should provide extensive uptake by Biofilm

and plant growth, as well as by sedimentation and filtration of suspended materials. Phosphorus

is stored in the sediments, biota, (plants, Biofilm and fauna), detritus and in the water. The

interactions between compartments depend on environmental conditions such as redox

chemistry, pH and temperature. The redox status of the sediments (related to oxygen content)

and litter/peat compartment is a major factor in determining which phosphorus cycling processes

will occur. Under low oxygen conditions (low redox potential), phosphorus is liberated from the


31

sediments and soils back into the water column, and can leave the wetland if the anaerobic

condition is not reversed (Okun 1979).

2.12 CWs in Suspended solids removal

Solids may be derived from outside a wetland (e.g., inflows and atmospheric inputs), and from

within a wetland from plankton (zooplankton and phytoplankton), and plant and animal detritus.

With low wetland water velocities and appropriate composition of influent solids, suspended

solids will settle from the water column within the wetland. Sediment resuspension not only

releases pollutants from the sediments, it increases the turbidity and reduces light penetration.

The physical processes responsible for removing suspended solids include sedimentation,

filtration, adsorption onto Biofilm and flocculation/precipitation. Wetland plants increase the

area of substrate available for development of the Biofilm. The surface area of the plant stems

also traps fine materials within its rough structure.

2.13 CWs in Pathogen removal

Pathogens are disease-causing organisms (e.g., bacteria, viruses, fungi, protozoa, helminthes).

Wetlands are very effective at removing pathogens, typically reducing pathogen number by up to

five orders of magnitude from wetland inflows (Reed at al., 1995). The processes that may

remove pathogens in wetlands include natural die-off, sedimentation, filtration, ultra-violet light

ionization, unfavorable water chemistry, temperature effects, predation by other organisms and

pH (Kadlec & knight 1996).They showed that vegetated wetlands seem more effective in

pathogen removal, since they allow a variety of microorganisms to grow which may be predators

to pathogens.

2.14 CWs in Heavy metal removal

Heavy metals is a collective name given to all metals above calcium in the Periodic Table of

Elements, which can be highly toxic, and which have densities greater that 5g/cm3

(Skidmore ,

1983). The main heavy metals of concern in freshwater include lead, copper, zinc, chromium,

mercury, cadmium and arsenic. There are three main wetland processes that remove heavy

metals; namely, binding to soils, sedimentation and particulate matter, precipitation as insoluble

salts, and uptake by bacteria, algae and plants (Kadlec, 1996). These processes are very effective,


32

with removal rates reported up to 99% (Reed et al., 1995). A range of heavy metals, pathogens,

inorganic and organic compounds present in wetlands can be toxic to biota. The response of

biota depends on the toxin concentration and the tolerance of organisms to a particular toxin.

Wetlands have a buffering capacity for toxins, and various processes dilute and break down the

toxins to some degree.

2.15 Abiotic Factors and their Influence on Wetlands

2.15.1 Oxygen

Oxygen in wetland systems is important for heterotrophic bacterial oxidation and growth. It is an

essential component for many wetland pollutant removal processes, especially nitrification,

decomposition of organic matter, and other biological mediated processes. It enters wetlands via

water inflows or by diffusion on the water surface when the surface is turbulent. Oxygen also is

produced photosyntheticcally by algae. Plants also release oxygen into the water by root

exudation into the root zone of the sediments. Many emergent plants have hollow stems to allow

for the passage of oxygen to their root tissues. The oxygen-demand processes in wetlands

include sediment-litter oxygen demand (decomposition of detritus), respiration (plants/animals),

dissolved carbonaceous BOD, and dissolved nitrogen that utilizes oxygen through nitrification

processes (Kadlec & Knight, 1996). The oxygen concentration decreases with depth and distance

from the water inflow into the wetland. It is typically high at the surface, grading to very low in

the sediment –water interface.

2.15.2 pH

The pH of wetlands is correlated with the calcium content of water (pH 7 = 20 mg Ca/L).

Wetland waters usually have a pH of around 6-8 (Kadlec and Knight, 1996). The biota of

wetlands especially can be impaired by sudden changes in pH.

2.15.3 Temperature

Temperature is a widely-fluctuating abiotic factor that can vary both diurnally and seasonally.

Temperature exerts a strong influence on the rate of chemical and biological processes in

wetlands, including BOD decomposition, nitrification and denitrification.


33

2.16 Sludge drying

All types of emergent macrophytes systems contain at least one species of rooted emergent

aquatic macrophytes planted in some type of medium (usually soil, grave, or sand).Many plant

systems e.g. Typha, Phragmites,and Scirpus (Schoenoplectus), are capable of not only becoming

readily established in the various materials but also grow efficiently and assist in the treatment of

the various systems. (Alexander & Wood (1987)

Emergent macrophytes systems are, amongst other systems, in use for the dewatering of Sludges.

The main reason for dewatering of the sludge is that it will decrease the transport and handling

costs. Other reasons are that the high water content will be a problem when sludge is used for

(co)-composting and also when the sludge is incinerated or disposed of to a landfill. Reed beds

are used for dewatering and mineralization purposes as reed is expected to improve the treatment

performance. The sludge is dried and together with the reed finally turned into compost, which

can, for example, be applied as soil amendment or as landfill cover. The reed bed for the

dewatering of sludge is composed of selected media supporting emergent vegetation and the

flow path for liquid is vertical. The sludge is spread over the system and accumulates there for a

period of considerable period of time - up to 8-10 years (depending on the loading rate, the

capacity of the system and the mineralization rate).The pollutants are removed through a

combination of physical, chemical, and biological processes including sedimentation,

precipitation, adsorption to soil particles, assimilation by the plant issue, and microbial

transformations (Brix, 1994).The penetration of the stems of the plants (reed) through the

different layers of sludge maintains adequate drainage pathways; evaporation takes place over

the whole reed bed area and the plant contributes directly to dewatering through

evapotranspiration. The root system of the vegetation absorbs water from the sludge, which is

then lost to the atmosphere via evapotranspiration. For European and US conditions it is

estimated that during the warm season the evapotranspiration can account for up to 40 percent of

the liquid applied to the bed.

Aerobic conditions in the soil or filter medium are maintained through the combination of root

rhizome penetration, oxygen transfer which boosts the population and activity of naturally

occurring micro-organisms and the mechanical effect of the tall reeds rocking in the wind. This

will result in aerobic conditions on or near the root surfaces in an otherwise anaerobic

environment which will enable different complementary microbiological processes to take place


34

in the soil of the reed bed (Reed et al., 1994). The reeds fed with wastewater or sludge grows

rapidly in the nutrient-rich medium and absorbs some of the minerals and water. Heinss et al.

(1998) assumes that reed beds are a feasible treatment option for faecal sludge treatment.

Compared to unplanted sludge drying beds, from which require dewatered of dried sludge

removal every few weeks or months, the sludge and reeds may have to be removed after several

years, as the root rhizome maintains the permeability of the filter and the increasing sludge layer.

Not much is known about the application of reed bed systems for the treatment and resource

recovery of the nutrients, organic matter and water present in faecal sludge. There is, however,

quite some experience with macrophytes systems used for the mineralization of sewage sludge

from activated sludge plants. Sewage sludge is to some extent comparable with faecal sludge as

argued in chapter 2. Therefore, examples of sewage sludge treatment may also represent the

possibilities for faecal sludge treatment.

Most popular for application in dewatering beds is the common reed (Phragmites) which is

usually planted in centres of 30 cm. Reed et al. (1994) mention that reed beds are not suitable for

the application of raw sludge (and thus not for FS as well) due to the high organic content which

will overwhelm the oxygen-transfer capacity of the plants. Strauss et al. (1999a), however, report

that the treatment of faecal sludge is possible when a ventilation system is installed, which

increases the oxygen input into the filter bed. A design criterion of 2.5 m2/p.e. for a minimal

planted surface is given by Boutin (1987) based on one population equivalent of 40g of BOD,

100g of COD and 150 litres (what means that it has a sewage character). Usually an area of 4 -

10 m systems for wastewater treatment.52/p.e is used for macrophytes

2.16 Sludge composting

The objective of sludge composting is to biologically stabilize putrescible organics, destroy

pathogenic organisms, and reduce the volume of waste (Tim Evance 2003). During composting

organic material undergoes biological degradation, resulting in a 20 to 30 percent reduction of

volatile solids (Imhoff Karl et al 1971).

In composting, aerobic microorganisms convert much of the organic matter into carbon dioxide

leaving a relatively stable odor free substance which has some value as a fertilizer (J.Jeffrey

pierce.et al 1998). Eccentric micro-organisms are also destroyed due to the rise in temperature of

the compost.


35

Composting includes the following operation:

a. Mixing dewatered sludge with a bulking agent.

b. Aerating the compost pile by mechanical turning or the addition of air.

c. Recovery of the bulking agent.

d. Further curing and storage.

e. Final disposal.

The resulting end product is stable and may be used as a soil conditioner in agricultural

applications. Aerobic composting is more commonly used than anaerobic composting (Tim

Evance 2003) the aerobic composting process is exothermic and has been used at the household

level as a means of producing hot water for home heating. The major advantage of this is

compost is a very good fertilizer but it is not much used yet (J.Jeffrey pierce.et al 1998)

2.16.1 Advantages of compostingComposting is an important treatment process for many organic wastes and residues, including

animal manure, municipal and industrial sludge, and solid or semisolid crop residues.

Major Advantages of Composting

• It produces a biochemically stable product that has low odor and good physical properties, and

it attracts few flies.

• It significantly reduces the volume of material that must be stored, transported, disposed of, or

used.

• It is a forgiving, robust and simple process that can be done on-site without a tremendous

investment in heavy infrastructure.

The improved physical properties of compost include low moisture content (usually below 35

percent by mass), more uniform particle size, friable texture, reduced volume and reduced

weight. These propertieslower the hauling costs per unit of active ingredient and make it easier to

spread the material uniformly. Aerobic, thermophilic composting also inactivates or kills most

pathogens and weed seeds.Phosphorus, potassium and other mineral elements are retained in

composted material. While ammonia nitrogen may be volatilized, or lost to the atmosphere as a

gas, total nitrogen usually remains stable as a proportion of total dry matter. Because of those

advantages, there is greater market potential for compost than for un-stabilized organic wastes.

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|CHAPTER THREE

36

CHAPTER THREE

MATERIALS AND METHODS

Abstract

This chapter gives detail information on materials and methods used in the accomplishment of

this study. This includes Laboratory analysis of Wastewater for Physicochemical and biological

parameters which conducted at Ardhi university laboratory, Field activity of sludge depth

measurement and experiment study of Sludge stability test which was carried out at Ardhi

university research center.

3.0 Location of the study area

The Salasala faecal sludge management system is located at coordinates 6°40ʹ58.16ʺS, 39°

11ʹ30.11ʺE, Tegeta ward, Kinondoni municipal, Dar es Salaam-Tanzania, and is elevated about

47m above the sea level. The area is bounded by Mtongani in east, Mbopo in west, Manyema in

south and Wazo in North. The case study area can be accessed via Bagamoyo, Scansca and

Upendo roads.

Figure 3.0: Topographical map of the study area

Salasala Treatment

Bagamoyo road

Scansca road


37

Plate 3.1 Orthophotographic map of the case study area (source: Google earth)


38

3.1 Climatic condition

The climate of Salasala as other part of Dar es Salaam is characterized as hot and humid coastal

tropical climate with high day and night temperatures with an annual mean maximum of 30.5 0C

and annual average of 250C. Additionally it is characterized by high humidity range in between

60 – 73% and heavy rainfall of above 1000mm per year, the long rainy season spines from

March to May and short season from November to December.

3.2 Existing situation

Salasala faecal sludge management system was established by the private owner Mr. Macha on

June 2007.The treatment system receive only domestic wastewater from pit latrine and septic

tank systems by means of his private two cesspit emptier of 5000 liters volume capacity each for

discharge fee of 60000=/Tsh per track . The treatment system comprises a screen chamber, one

Pond and one horizontal surface water flow constructed wetland. Wastewater flow through the

system is by gravity, the vacuum truck discharge the effluents though the plastic pipe of about

12cm diameter to the screen where’s start to flow through the system by gravity (Ref Figure3.1

below). The system effluent is collected and pumped to irrigate two plots of banana farm of

about 2023m2 in size, one is located near the treatment system and another is contiguous the

owner house.

From vacuum track

Low lift pump

Figure 3.1 Schematic diagrams of Salasala Faecal sludge treatment system

Screen Sludge Pond Constructed wetland

Storagetank

Banana farm


39

3.2.1 System description.

3.2.1.1 Screen chamber

The Salasala faecal sludge management system is consisting of a one hand cleaned course

screen. A screen chamber have the size of (2.5 m×2m) in dimension and consist of a bar racks of

10mm diameter with 45mm clear spacing between the bars. The screen removes coarse materials

from the influents that could cause damage and blockage of the sysytem and also from setteld

sludge that will inhibit the beneficial reuse of biosoil. From the screen chamber, the sludge

flows by gravity to the pond.

Plate 3.2 Screen chamber

3.2.1.2 Sludge pond

The Faecal sludge systems have only one faecal sludge pond of length to width ratio (Aspect

ratio) of 2.The effective pond dimension is 31.8 m length, 16 .2m width and 1m depth, is used to

retain faecal sludge and its contents to allow physical separation and biological treatment of

pretreated faecal sludge and wastewater to occurs and later, wastewater enters the constructed


40

wetland system where auxiliary treatments proceed. According to the owner of the faecal

sludge management system, since the system was constructed year 2007, the sludge pond has not

dislodged.

Plate 3.3 Salasala Faecal sludge pond

3.2.1.3 Constructed wetland system

Salasala faecal sludge system also comprises a constructed wetland system of 56m length, 1.1m

width and 0.6 m depth. The constructed wetland system which used for additional treatment of

wastewater from sludge pond is located adjacently into the pond system. During research

investigation it was found that, the wetlands system does not contain aquatic plants

(macrophytes) and during interview with facility owner, he said that he was about to plant


41

aquatic plants to his wetland system but he have not clear acquaintance of what type of aquatic

plant are implanted on constructed wetlands.

Plate 3.4 Constructed wetland system

Plate 3.5 Banana farm irrigated with final effluent


42

Plate 3.6 Farm irrigated with final effluent (source: Site survey)


43

3.3 Materials

3.3.1Sludge depth measurements

Plate 3.7 Depth measurement Plate 3.8 A tape measurer fixed on a rod

3.3.2 Wastewater Sampling

Four wastewater sample points were established at various point of the Treatment system, at the

inlet of the pond, at nearly middle of the pond, at the outlet of the pond (also inlet of the

constructed wetland) and at the outlet of wetland system. The samples were collected in 1000ml

bottles for analysis at Ardhi University Laboratory. A total number of 16 representative samples

were collected during research investigation.

The sludge depths of the pond system were measured by configuring offshore coordinate system

along the breadth and span bank of the pond. At each point X, Y of orthogonal projection, the

depth of the sludge were taken with a white tape measure fixed to adjacent end of the rod.

The white tape measure was allowed to stay for a while in the sludge at a specific point to give

clearand visible reading


44

Figure 3.2 Wastewater sampling points

3.3.3 Faecal sludge sampling

Five sampling points of faecal sludge were established. Two points of triple samples vertically

down is within sludge zone locality (i.e. sample of upper, nearly middle and bottom sludge

layer), two points of single sample at Water zone locality and one point at the middle of the pond

(Ref Figure 3.2 below).The number of samples that taken were selected based to the profile and

accumulation of the faecal sludge in the sludge pond. Point of higher accumulation and high

sludge depth, three samples were taken.

Figure 3.3 Faecal sludge sampling points


45

3.3.3 Equipment’s used

Physical parameters such as pH and Temperature were measured using pH C101 probe

connected to pH meter (HQ30d) HACH product, HACH Sension 6 - DO meter, HACH

Sension156 conduct meter capable of measuring specific conductivity, TDS and Salinity.

Chemical parameters N-NH3, PO4 were measured using HACH DR/2010 Data logging

spectrophotometer and Calorimetric with test strip methods respectively. Biological parameters

such as COD and BOD5, were measured using EMDC1 1173: Part 4 Dichromate Digestion

Method, Ratio method i.e. (COD: BOD=2:1) and Membrane filtration method using nutrient

agar and MacConkey for Faecal coliform FS and Total coliform measurements. Sludge stability

experimental setup equipment’s such as syringe, rubber stoppers, plastic pipes, 1000mls and 350

mls bottles for wastewater and faecal sludge collection and setup. Other equipment includes

beakers, petri-dish, test tubes, pipette, measuring cylinders and aluminum foil.

Plate 3.7: Spectrophotometer Plate 3.8 Membrane filtration system

3.3.4 Reagents used

Reagents and chemicals for COD determinations and physicochemical parameters used include

Sulphuric acid (H2SO4) and Potassium dichromate, Ammonia salcylicate, ammonia cynurate,

reagent Distilled water for sample dilution and minimization of sample concentration during

analysis, the known concentrations of the samples used for spectrophotometer calibration; For


46

sludge stability experimental setup only sodium hydroxide (NaOH) was used. For other

parameters, only distilled water was used to rinse the probes of the equipment’s and for solutions

preparation.

3.4 Methods

3.4.1 Site visits and interview

Site visiting was conducted to have a visual inspection of the real situation of Salasala faecal

sludge treatment system. These also include interview of the facility owner Mr Macha and the

household nearby treatment system to get their views upon Salasala faecal sludge management

system and identify the major problems caused by having treatment system nearly their house

vicinity. Six households were interviewed

3.4.2 Experimental setup for sludge stability

Figure 3.4 Schematic diagram of typical experimental setup

NaOH + H2O

Experiment was conducted to determine sludge pond stability .The sludge samples were

collected from Salasala faecal sludge pond and experimental setup was done at Ardhi University

Research center. According to the sample taken, nine set of sludge stability test experiment were

established. Single set of sludge stability test experiment system was comprises three reactors

[Figure 3.3 demonstrates]; The first is the substrate reactor which contain a one liter of a sample

sludge, Second is the gas collector reactor which contain a solution of 15% sodium hydroxide

(NaOH) and distilled water and third a water collector reactor. The monitoring was done

by measuring the volume of water displaced in 24 hours interval for 14days duration to

determinethe amount of water displaced.


47

Plate 3.9 Experimental setup of sludge stability test

3.4.3 Analysis

3.4.3.1 Physical parameters

Conductivity, Total Dissolved Solids (TDS) and Salinity were measured by a calibrated Hach

Sension156 conduct meter in Micro Siemens per centimeter, µS/cm or mS/cm, mg/L and ‰

respectively. Temperature and pH were measured using HANNA meter HI 8424 with pH and

temperature probes.

3.4.3.2 Chemical parameters

Chemical parameters NH3-N and PO4 were measured by using Portable Data logging HACH

DR/2010 spectrophotometer instrument and Calometric method with test strips in milligrams per

liter respectively.

Substrate reactors

Gas collector reactors

Watercollectorreactors


48

Plate 3.5 Laboratory Sample analysis for physical parameter

Plate 3.8 Laboratory sample dilution for of chemical parameters analysis

So1

So2 So3


49

3.4.3.3 Chemical Oxygen Demand

1.5 ml of potassium dichromate mixed with 3.5 concentrated Sulphuric acids was prepared in the

test tube. 2.5 mls of sample was added in a test tube containing strong oxidizing agents, followed

by thorough mixing, these processes were carried out in the fume chamber. The solutions were

digested in the hot oven for 2 hrs at 150 oC and kept to cool at room temperature. Then using

Spectrophotometer (Portable Data Logging Spectrophotometer) at wavelength of 600 nm COD

was measured in mg/L, by first putting the blank solution into cuvert (containing only strong

oxidizing agent and distilled water) for zeroing to calibrate the machine followed by reading the

solutions containing the samples

3.4.3.4 Faecal and Total coliforms (FC &TC)

1 ml of Wastewater sample was measured using a sterile measuring cylinder, then diluted with

99ml of sterile distilled water to make a total dilution of 100ml. Another 1 ml from 100mls

diluted was taken and mixed with 99mls of sterile distilled water. Another dilution was done to

make a dilution factor of (×106 ).The vacuum pump was assembled, the filtration funnel was

rinsed by using hot water for the purpose of sterilization and the filter paper was placed just

below the filter funnel, 100ml of diluted sample was sucked through the filter paper using

vacuum pump. Then the filtration apparatus was disassembled and carefully by using sterile

forceps, the filter paper was transferred onto a petri dish containing nutrient agar for fecal

Coliform test and mackonkey for Total coliform. Both petri dishes of faecal coliform and total

coliform test were bind together, labeled and incubated at 440C and 340C respectively for 24

hours.

3.4.3.5 Data analysis and computationsThe data from laboratory, experimental setup and from site measurements were analyzed and

computed by using computer programs such as Microsoft Office Excel 2010 and AutoCAD

2012. Descriptive statistics tool in Microsoft Office Excel 2010 was mainly used to determine

various statistics of interest.

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|CHAPTER FOUR

50

CHAPTER FOUR

DATA RESULTS AND DISCUSSION

Abstract

4.1 Wastewater characteristics

PH

The highest mediocre pH value was 6.7 observed in two samples S02 & S04; these were the

samples from middle of the pond (S02) and outlet of constructed wetland (S04). pH is a

measurement of the concentration of hydrogen ions (H+) in solution. Lower and higher pH

reaching alkaline and Acidity, hamper biological treatability of sewage, it also makes irrigated

soil to be acidity and alkalinity depends on amount of water used to irrigate. For irrigation, pH

has no direct effect on plant growth; however, it does affect the form/availability of nutrient

elements in irrigation water, fertilizer solutions and the growing medium. The wastewater pH of

Salasala plant for different localities of the treatment facility varies slightly throughout the

system (indicated in Fig 4.1).However the effluent pH is within the standards, the pH range

recommended by TBS is 6.5-8.5.

Temperature

Figure 4.2 shows the variations of temperature along the treatment system. It was noticed that the

temperature variation along Salasala faecal sludge treatment system increases slightly from 27.6

This chapter gives results and discussions of physicochemical and biological properties of

Wastewater, sludge stability test, various assessments such as Economic and aesthetics

assessment. It also outlines the essential improvements of Salasala Feacal sludge treatment

facility.

4.1.1 Physical Characteristics

The requisite of determine Physical characteristics of wastewater are to assess both condition of

waste water in treatment facility as well as its effect caused on reuse for irrigation. The physical

characteristic of wastewater of Salasala faecal sludge management system is tabulated in

Appendix 01.


51

at inlet of the pond (sample S01) to 28.2 at outlet of constructed wetland (S04) which implies that

wastewater treatment plant is not effective enough as it tend to influence temperature along the

system. However temperature is within the standards; the TBS range for Temperature is 20-35 °.

Total dissolved solids (TDS) and Total suspended solids (TSS)

The Total dissolved and suspended solid variation throughout the treatment system is indicated

in Fig 4.3 and 4.4 respectively. As figures indicate, both TSS and TDS decreases throughout the

system: TSS decreases from 1325 to 251.5 mg/l and TDS from 1616.5 to 1167.25 mg/l, which

infers sewage stabilization occurs nevertheless the effluent TSS is not in the standards and TDS

is still strong, the TBS standards for TSS is 100mg/l and the typical domestic wastewater have

TDS of range from 200-week, 500 medium, 1000-stong (Metcalf and Eddy 2003) .This is

implies that the efficiency of Salasala faecal sludge system in wastewater treatment is not

sufficient enough.

Conductivity and Salinity

Conductivity and salinity are used to acquaint the presence of soluble ions such as salt ions in

wastewater. Eminent levels of salt can have detrimental effects on production system and the

environments. Throughout the treatment system [indicated in Figures 4.5 and 4.6], Conductivity

decreases from 3.13 to 2.41 mS/cm and Salinity from 1.5 to 1.03 ‰ .Though the system reduced

Conductivity and salinity but it does not reach the required permissible amount.

Color and turbidity

Colour and turbidity are used to assess aesthetical value of wastewater. Turbidity in water is

caused by suspended and colloidal matter such as clay, silt, finely divided organic and inorganic

matter, and plankton and other microscopic organisms. In wastewater reuse for irrigation, highly

turbid wastewater may choke irrigation system. Color and Turbidity of wastewater of Salasala

system plant, decreases from inlet to final effluent along system [indicated in figures 4.8 and

4.9]. Turbidity decreases from 1124.5 NTU to 500 NTU and Colour from 3175 to 900 mg Pt-

co/l. This shows treatment of wastewater occurs and mostly with constructed wetland as gradual

change observed between inlet and outlet of constructed wetland for both Color and turbidity.

However the wastewater effluent for both color and turbidity does not reaches the required


52

permissible amount. TBS standards for color and turbidity effluent from wastewater treatment

system are 300 NTU and 300 mg Pt-co/L respectively.


53

Figure 4.1 PH variations along the treatment plant.

Figure 4.2 Temperature variations along the treatment plant

6.60

6.73

6.65

6.73

6.526.546.566.586.606.626.646.666.686.706.726.74

S 01 S 02 S 03 S 04

PH

PH

27.6727.60

28.15

28.27

27.20

27.40

27.60

27.80

28.00

28.20

28.40

S 01 S 02 S 03 S 04

Temperature (°c)

Temperature (°c)


54

Figure 4.3 TDS variation along the treatment plant

Figure 4.4 Total suspended solid variations along the treatment plant

S 01 S 02 S 03 S 04TDS (mg/l) 1616.50 1203.25 1220.25 1167.25

0.00

200.00

400.00

600.00

800.00

1000.00

1200.00

1400.00

1600.00

1800.00

TDS

(mg/

l)TDS (mg/l)

S 01

S 02

S 03

S 04

1325.00

407.50

407.50

251.50

Total suspended solid TSS, (mg/l)Total suspended solid TSS, (mg/l)


55

Figure 4.5 Conductivity variations along the treatment plant

Figure 4.6 Salinity variations along the treatment plant

3.13

2.05 2.11

2.41

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

S 01 S 02 S 03 S 04

Conductivity (ms/cm)

Conductivity (ms/cm)

Con

duct

ivit

y (m

s/cm

)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

S 01 S 02 S 03 S 04Salinity (%) 1.50 1.23 1.13 1.03

Salin

ity

Salinity (‰)


56

Figure 4.8 Colour variations along the treatment plant

Figure 4.9 Turbidity variations along the treatment plant

3175.00

2325.002275.00

900.00

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

3500.00

S 01 S 02 S 03 S 04

Colour (mg Pt-co/l)

Colour (mg Pt-co/l)

Col

our

(mg

Pt-

co/l)

S 01 S 02 S 03 S 04

1124.50

725.00825.00

500.00

Turbidity (NTU)

Turbidity (NTU)


57

4.1.2 Chemical characteristics

The Chemical characteristics of wastewater have been obtained though analysis of a toxic

pollutant Ammonia-nitrogen NH3-N (mg/l) and a nutrient phosphate in terms of PO4 (mg/l).

Chemical characteristics of wastewater are presented in Appendix 02:

Ammonia-nitrogen (NH3-N)

Ammonia nitrogen (NH3-N) is a measure of the amount of ammonia, a toxic pollutant often

found in sewage, waste products, liquid manure and other liquid organic waste products.

Ammonia can directly poison humans and upset the equilibrium of water systems. In Salasala

treatment plant, the percentage of ammonia reduction from inlet to outlet of the system plant is

about 41.93%, the other 58.07% which is more than half of inlet amount is disposed to the

environment through irrigation.

Although ammonia reduction occurs along the system plant as figure 4.10 indicates, but the final

effluent doesn’t grasp the wastewater effluents permissible amount. A TBS standard for total

nitrogen concentration is 15mg/l contrary to 129.67mg/l of final effluent. Thus, the above

signposts efficiency shows that Salasala plant is not efficient enough in ammonia nitrogen

reduction from wastewater.

Phosphate (PO4)

Phosphate (PO4) is one of the important chemical nutrients in wastewater used for irrigation as it

provides nutrient (phosphorous) which is the one of the essentials plants nutrients. While its

important wastewater parameter for agriculture and which its excess in the receiving

environments cannot easily physically observed, effluent limit must be adhered. TBS effluent

standard of phosphate is 6 mg/l .Though treatment reduction happens [As Figure 4.11 spectacle]

but efficiency of treatment is not ample. From inlet to outlet the percentage of phosphate

removed is about 42.85%, the other 57.15% is not removed.


58

Figure 4.10 Ammonia-nitrogen variations along the treatment plant

Figure 4.11 Phosphate variations along the treatment plant

Sample 01 Sample 02 Sample 03 Sample 04NH3-N (mg/l) 223.33 151.00 155.33 129.67

0.00

50.00

100.00

150.00

200.00

250.00

NH3

-N (m

g/l)

NH3-N (mg/l)

500.00

200.00

150.00200.00

0.00

100.00

200.00

300.00

400.00

500.00

600.00

Sample 01 Sample 02 Sample 03 Sample 04

PO4(mg/l)

PO4 (mg/l)


59

4.1.3 Biological characteristics

The biological characteristic of Wastewater of Salasala faecal sludge treatment plant system was

measured in term of COD, Faecal coliforms and Total coliforms bacterial. BOD5 in 20°C was

calculated from assumption ratio of COD: BOD = 2:1.

COD test is used to determine the oxygen equivalent of the organic matter that can be oxidized

by a strong chemical oxidizing agent (potassium dichromate) in an acid medium. On other side

the BOD5 is the important parameters because it determines the amount of oxygen required to

stabilize waste biologically. Other parameters such as faecal coliforms and Total coliforms

bacterial are used to assess and to identify presence of pathogens and’ specific organisms in

connection with plant operation and effluent re-use. The biological characteristics of Salasala

plant wastewater is tabulated in Appendix 03:

COD (mg/l)

Chemical oxygen demand in the system, measures the total amount of Oxygen needed to oxidize

organic carbon present in wastewater .A higher value of COD signifies that wastewater has large

amount of organic matters. Faecal sludge treatment plant efficient on organic matter reduction is

not utterly sufficient comparing to the recognized minimum allowable standards of wastewater

effluents from wastewater treatment facilities. Though the treatment plant removes COD with

satisfactory efficiency of about 85% from inlet to outlet as fig 4.13 stipulates, but effluent

concentration of 636.67mg/l is far away from 60 and 50 mg/l a TBS and WHO standards. This

signifies that Salasala faecal sludge treatment system is not efficient enough in COD remove.

BOD5 (mg/l)

This is the important parameter in wastewater treatment and disposal because it articulates to

which extent wastewater will pollute the receiving water bodies. BOD5 gives the amount of

Oxygen needed to oxidize organic waste biologically. The Salasala plant efficient in BOD

remove as calculated is not enough as per recognized minimum allowable standards of

wastewater effluents from wastewater treatment facilities. As Figure 4.12 bellow demonstration,

BOD removed from wastewater along the system plant is about 1935mg/l which is 85.88% of the

BOD at the inlet point of the system. Though system reduces BOD with good efficiency,


60

nonetheless the final effluent BOD concentration doesn’t grasp the required standard. TBS

standard for BOD5 in 20°C is 30(mg/l).

Figure 4.12 BOD5 variations along the treatment plant

Figure 4.13 COD variations along the treatment plant

0

500

1000

1500

2000

2500

Sample 01Sample 02

Sample 03Sample 04

2253

10401015

318

BO

D5(m

g/L

)

BOD5 (mg/l) at 20 °C

BOD5 (mg/l) at 20 °C


4507

2080 2030

637

COD (mg/l)COD (mg/l)


61

Total and faecal coliforms

Figure 4.14 Total coliforms variations along the treatment plant

Figure 4.15 Faecal coliforms variations along the treatment plant

58,000,000

37,666,667 35,333,333

22,333,333

0

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

60,000,000

70,000,000


Total coliform (Count/100ml)

Total coliform (Count/100ml)

24,066,667 23,333,33321,000,000

16,000,000

0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

30,000,000


Faecal coliform (count/100ml)

Faecal coliform(count/100ml)

Total and feacal coliform bacteria variation along the system plant is presented in figures 4.14

and 4.15 respectively. As figures indicated both total and faecal coliform decreases along the

system .The System plant removes 33.52% of the faecal bacteria of inlet point and 61.49% of the

Total coliforms of inlet point. However the effluent does not reach the required effluent

standards as tabulated in Appendix 03.


62

4.2 Pond Sludge stability and volume

The sludge pond stability was determined through analysis of data from sludge stability

experiment. Both stability and volume of the sludge pond were determined so as to gives the

efficiency of the system in stabilizing faecal sludge and sludge accumulation rates which later

will lead to proper suggestion of improvement ideas and scaling up the decentralized faecal

sludge management system to achieve better economies of scale, volume of the sludge present.

4.2.1Pond Sludge stability

The stable sludge can be defined as the sludge which has been treated to reduce volatile organic

matter, vector attraction and to reduce the potential of putrefaction and offensive odor. The more

organic the greater the gas produced and vice versa.

The vector attractiveness (frequently associated with odors and unsightliness) of sludge is an

important parameter in protecting public health and the public’s acceptance of bio solids land

application. Odor is the most common complaint. This is the currently accepted methods for

assessing vector attractiveness of anaerobically digested sludge.

4.2.1.1 Experimental results

Experimental results for stability test (i.e. the gas volume mL produced per day interval for

14days duration are summarized and tabulated in Appendix 04:

The fallouts shows that, the sludge on the pond has not yet stabilized enough as still it produces

methane gas though decreases in time [Figures 4.17 and 4.18 indicates] this indicates that the

sludge have either highly variable depending on the influent sludge characteristics or require an

exorbitant amount of time to complete. Therefore, the pond system is not performing well in

faecal sludge stabilization process and a need exists for establishing a more efficient and reliable

method to complete sludge stabilization so as to minimize the vector attractiveness of anaerobic

digested sludge


63

Figure 4.16 Sludge stability progress for different sludge sample

5536

25

4

70

10

70

35

75

0

300

0

100

15

75

36

90

50

0

100

200

300

400

500

600

700

800

900

1000

DAY01

DAY02

DAY03

DAY04

DAY05

DAY06

DAY07

DAY08

DAY09

DAY10

DAY11

DAY12

DAY13

DAY14

Gas v

olum

e (m

l)Volume of gas VS Days

S9

S8

S7

S6

S5

S4

S3

S2

S1

SAMPLE NAME DESCRIPTION

S1 Upper sludge sample from sampling point 01

S2 Middle sludge sample from sampling point 01

S3 Bottom sludge sample from sampling point 01

S4 Water zone sludge sample from South side of the pond

S5 Water zone sludge sample from North side of the pond

S6 Sludge sample from middle point of the pond





64

Figure 4.17: Cumulative gas volume of sludge samples

4.2.2 Sludge volume determination

Since the sides and base of the sludge pond are planes, the sludge volume was computed by

using a Spot height method of earth work volume estimation

The coordinates was configured onsite by interval of 2m along the span and breadth of the sludge

pond and sludge depth was taken at each intersection of x,y coordinates. [Figure 4.18 bellow

shows]

830

185

540

650

294

761.5

447

786

928

0

100

200

300

400

500

600

700

800

900

1000

S1 S2 S3 S4 S5 S6 S7 S8 S9

Cum

ulat

ive

gas v

olum

e (m

Ls)

Sampling points

Cumulative Gas volume vs Sampling points


65

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

2

4

6

8

10

12

14

16

Figure 4.18 Pond coordinate configuration

From Spot height method

Volume = plan area × mean height

Plan Area of one square = 2×2, A = 4m2

Therefore, volume for one square is given by

= 4 × 14 [h (0, 0) + h (2,0) + h(0,2) + h(2,2)]Where h(x,y) = sludge depth at x,y coordinates

The result is tabulated in Appendix 05:

The total sludge volume is 252.52 m3 equivalents to 55,546.6 gallons

Y (m)

X (m)

Inlet

Exit


66

4.3 Economic aspect of Salasala faecal sludge management system

Salasala private decentralized faecal sludge management system receives faecal sludge from the

community by means of two hauling private vacuum tracks of capacity of 5000 liters each, with

a total charge of 60000/= Tsh per trip. This total charge includes fee for, sanction, transportation

and dumping of faecal sludge. The table 4.5 summarizes the economic assessment of Salasala

faecal sludge management system.

As the Table 4.5 indicates, the Salasala Faecal sludge management facility makes a profit of

about 51,840,000 Tsh/= per year. The system looks economical, as it makes a profit of about

34.5% of the investment cost, however it does not recovers effectively all resources suitably

obtained through sludge management and treatment.


67

Plant size and sludgeload

Plant capacity 63.13 m3 FS/yTotal surface area 582 m2COD Loading 6100 mg/lBOD Loading 3050 mg/lPond capacity 512m3

Amount received peryear

Total charge /Trip/truck 60000.00Average trip/day/truck 3.50Amount received/day pertruck 210,000 (Tsh)Amount received permonth per truck 6,300,000 (Tsh)Amount received permonth for 2 trucks 12,600,000(Tsh)

Total (Tsh) 151,200,000.0Operation and

Maintenance cost (O+M)

Item Amount per dayAmount per

monthAmount per

yearLabour Salary and Fuelcost 250000.00 7,500,000.0 90,000,000.0

Car services and plantrepairing cost 150,000 1,800,000.00

Total (Tsh) 91,800,000.0Annual cost

Life time of the plant 4 yearsinterest rate [%] 0.05

Investment Cost (Tsh) 150,000,000.0

Profit per year

Profit per year = [Amount received per year-interest rate -(O+M)]Profit per year = [151200000-(150000000×5%) -91800000]

Profit per year = 51,840,000Total profit per year (Tsh/year) 51,840,000

Table: 4.5 Economic analysis of salasala faecal sludge management system


68

4.4 Aesthetics assessment

4.4.1Solid waste management

In any faecal sludge or wastewater treatment plant, solid matter and wastes from influent is

unavoidable. These wastes are mostly from pit latrine and other latrine types; these are simply

because latrines can be one of the local disposing points of domestic solid wastes. In Salasala

faecal sludge treatment plant, it was observed that solid waste exists mostly at the screen more

than any part of the system and other small part of solid waste is generated by surrounding plants

and human being, Also it was observed , there were no solid waste management activity taking

place.

Plate 3.9 Dumped Solid waste from screen

4.4.2 Odor and smell

From oral interview of plant nearby residents, complaints have been raised concerning odor and

smell especially during disposing of faecal sludge when the truck arrived. In one way or another


69

it has been source of arguments about the system performance and suitability on treating faecal

sludge. However they said that, few moments after disposing the smell disappears.

4.4.3 Surrounding Land Use

The Salasala surrounding land is mainly used for cultivating fruit crops such as Banana, okra,

African eggplants, salad, pawpaw’s, overdoes, mangoes etc. and grazing domestic livestock’s.

Waste water from the treatment system is used to irrigate adjoining farm, and small area

surrounding the system (on west side of the pond) is adjoin the resident houses.

Plate 3.6 Area used for grazing

4.4.4 Insect Attraction

It is quite common for insects to live and breed at faecal sludge treatment plants. Insects at

faecal sludge treatment plants become a problem when there are large populations of them, and

they create a nuisance for residents of neighboring properties.


70

However according to physical observation and interview of people surrounding the plant area,

no large populations of insects have been observed at the Home bush of Salasala pond in recent

years and there have been no complaints about insect nuisance associated with the Treatment

system.

4.4.5 Personal protective equipment’s (PPE’s)

Personal protective is one of the worth concern in any associated physical activity of which risk

can be Physical, Mental or personal health. In wastewater and faecal sludge treatment plants,

there are many risks which are associated with daily activities: In Salasala Faecal sludge

treatment plant it was observed that, workers wears Personal protective equipment’s during

activities.

Plate 3.7: Faecal sludge disposing activity conducted by worker wears PPE


71

4.5 System improvements required

The following are the system improvements required to make Salasala faecal sludge

management system suitable as well as efficient in faecal sludge management and treatment

4.5.1General improvements

4.5.1.1 Land use round system plant.As it was observed, the land use nearby Salasala treatment plant is for domestic livestock’s

keeping such as goats, chickens, pig and other agriculture activity, improvements attention of

isolating the system plant from such activity should be taken so as to minimize risk of human

and animal health against wastewater and faecal sludge vulnerabilities.

4.5.1.2 Solid waste management at the system plantOne of the prevalent grumbles of residents contiguous Salasala Faecal sludge system was

obnoxious odor from the system plant, as observed this is mainly caused by improper disposal of

plant solid waste specifically from screen and pond outlet. Therefore the system should have

solid waste treatment and disposal facility such as Incinerator.

4.5.1.3 Unit of sludge dewateringAny sludge treatment facility must have at least a single unit for sludge dewatering so as to

achieve a complete sludge treatment, unfortunately there was no any Sludge dewatering unit at

Salasala faecal sludge treatment system, Thus the system should have at least one sludge

dewatering unit.

4.5.1.4 Aesthetic and beauty of the surroundings system environmentThe faecal sludge and wastewater treatment facilities is supposed to have a beautifully, clean and

attractive environments. The Salasala surroundings environments are dirty, it is uninfluenced

area to stay even for a single minute which perhaps swaying people to argue about it suitability

on managing faecal sludge. The beauty can be achieved through different methods; one can

create a pleasant area though paving some important areas, creating gardens of beautifully

flowers with aroma smell and on top of that regular cleaners of the surroundings. Therefore this

should be taken into consideration.


72

4.5.1.5 Improvement’s to make Salasala faecal sludge management system cost effective

The cost effective system can be attained by increasing the system profit per year through

earn/recovery and selling more recourses from faecal sludge and its components i.e. More water

for irrigation through faecal sludge treatment, organic manure through composting of dislodged

faecal sludge and energy as biogas , the followings are improvements which required;

More water through sludge treatment

More water can be recovered principally by preventing water loss from the system typically

through underground and side wall seepage by minimize the system leakages through

lining/coating the walls of system units especially the pond with a cement materials so as to

minimize both underground side wall infiltrations

Energy recovery as biogas

As sludge stability test shows in Appendix 04: The average amount of gas generated in 14 days

by 1L of a sludge sample is about 602.3889 m3 or 43.0278m3/day .Each cubic meter (m3) of

biogas contains the equivalent of 6 kWh of calorific energy. However, when biogas is converted

to electricity, in a biogas powered electric generator, only 2 kWh of useable electricity is

obtained, the rest turns into heat which can also be used for heating applications.

For sludge volume of 252.52m3, more than 10,876,036.4 m3 of gas can be generated per day

which is about 21,752.07 mWh. Therefore there is a need of modifying the system pond (to be

biogas reactor) so as to capture the biogas produced and hence economic system.

Organic manure through composting

The sludge can be composted with organic solid waste and organic fertilizer can be

wholesaled and another used to raise plants and thus the profit can be made through selling

the organic manure as well as plant sprouts of different species


73

4.5.2 Specific improvements

4.5.2.1 Constructed wetland system improvementsThrough physical observation and interview it was observed that a Constructed wetland system

is not properly designed and it does not contain any biological macrophytes plants. A constructed

wetland is a system that utilizes natural processes involving wetland vegetation, soils, and their

associated microbial assemblages to assist, at least partially, in treating an effluent or other water

source. It comprise plants species such as Typha, Cyperus latifolius, cyperus papyrus,

hydrocotyle, hydrocleis etc, in general, these systems should be engineered and constructed

outside naturally occurring flood plains. The degree of wildlife habitat provided by a constructed

wetland, or sections of such wetlands, varies broadly across a spectrum. At one end of the

spectrum are those systems that are intended only to provide treatment for an effluent or other

water source, in order to meet the requirements of treating the wastewater, and that provide little

to no wildlife habitat.

Therefore this can be taken as the major improvements that’s must be considered particularly to

improve pollutants removal efficiency, as per laboratory chemical analysis results a constructed

wetland system have little efficiency in Ammonia-Nitrogen reduction and virtually negative

efficiency in nutrient phosphorous removal Ref (Fig 4.10 and 4.11)

The other improvement consideration is redesigning of a constructed wetland system or perhaps

goes to another type of constructed wetland system.

4.5.2.2 Sludge pond improvementsThe following are the improvement required to surge up pond performance as well as to make it

suitable sludge management entity.

Pond Geometry

The optimal pond geometry is that which minimizes hydraulic short-circuit. Preventing flow

short-circuiting through a pond will maximize retention time and improve final effluent quality.

In general, rectangular anaerobic ponds have length-to-breadth ratio of 2-3 to 1 so as to avoid

sludge banks forming near the inlet, unfortunately the location of inlet and outlet of Salasala

system pond was observed to be on the same side of the pond. Therefore the inlet and outlet is

required to be located in diagonally opposite corners of the pond.


74

Inlet and Outlet Structures

The inlets to anaerobic ponds typically discharge well below the liquid level to minimize short

circuiting and to make easily for the new incoming sludge’s be readily contact with presentbiological sludge and hence maximize sludge pond stabilization efficiency and odor reduction

which are primary objective of sludge ponds. For recommendation of inlet structure, see

Figure4.20 for anaerobic pond

Figure 4.20 Inlet arrangement of anaerobic pond

Pond sides walls

Like any other open water retain structures, side wall protection trough lining and inclination

is important as it reduces side erosion and increases side stability against water surge and

pressure and hence the structure will operate safely thought its design life. This also is the

improvements which should be taken to improve salasala pond performance as it was

observed the side walls of the pond is not lined/coated with a cement materials and is

orthodox vertical.

Dislodge of the sludge pond

From sludge volume measurements a sludge pond have found to have about 252m3 of sludge

volume which is almost 50% of the volume of pond 512m3and have not been dislodged since

the system was started to operate 4years ago. Therefore the sludge should be dislodged from

sludge pond as also it depreciates its performance, sludge stability test reveal this.

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|CHAPTER FIVE

75

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.0 CONCLUSION

The primary objective of this study was to assess Salasala privately operated decentralized faecal

sludge management system and critically to analyze the improvements which are needed to make

it suitable (cost effective) faecal sludge management system with a potential for citywide

adoption.

The physicochemical and biological characteristics of system wastewater for essential

parameters such as Color, Turbidity, total suspended solids, Ammonia nitrogen, COD, BOD5,

faecal coliform and total coliform was observed to be not within minimum permissible amount

[i.e. TBS and WHO]. Additionally, sludge stability test has shown that, the system is not

performing well in sludge stabilization process and the pond system of a volume of 512m3 have

the sludge volume of about 252m3 which is almost 50% of the volume of pond and have not been

dislodged since the system was started to operate 4years ago.

Furthermore the system surrounding’s was observed to be unpleasant, dirty and dull and there

was no solid waste handling activity from treatment facility. However the system was found to

be economical, as it makes a profit of about 51,840,000=/T.sh per year and has a benefit

economic ratio (BCR) of about 1.6

From these observations it can be concluded that, Salasala Faecal sludge treatment system is not

effective enough in Feacal sludge and wastewater treatment activity for final effluent to be used

for irrigation and agriculture activities and also it does not effectively recover all resources

suitably obtained through sludge management and treatment.

ARDHI UNIVERSITY Dissertation by Ulotu Gerald |5.1RECOMMENDATION

76

5.1 RECOMMENDATION

From the results obtained in this research, the following are recommendation

Since the treatment plant is not work efficiently, there is the need of system owner to act

upon stated improvements and hence to bring the effluent quality to the acceptable

standards of irrigation as well as to make the system to be suitable faecal sludge

management system.

A need exists for establishing a more efficient and reliable method of treating faecal

sludge to complete sludge stabilization and thus minimizes the vector attractiveness from

anaerobic digested sludge.

Soon after mentioned improvements are implemented there should be a regular checkup

of the performance of the treatment plant so as to assess its performance.

Forward-thinking on the study may be made on the investigation of presence of heavy

metals in the system wastewater which will be from utilization of personal beauty

products, maquillages, Antibiotic’s and other home use medicines

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|REFERENCES

77

REFERENCES


78

REFERENCES

Alexander, W.V.; A. Wood, 1987, Experimental investigations into the use of emergent

plants to treat sewage in South Africa, Water Science and Technology, Vol.19

Center for Water Resources Studies (CWRS), Dalhousie University. Septage

Management and Treatment Final Report: Domestic Septage Management Review,

1999.

Cooper P F, Job G D, Green M B and Shutes R B E (1996) Reed Beds and Constructed

Wetland for Wastewater Treatment, WRc Swindon, UK

Denny, P., 1997, Implementation of constructed wetlands in developing countries, Water

Science and Technology, Vol.35, No.5, pp 27-34

Estrada, Dr. Roberto Cáceres, Dr. Armando Cáceres, Alan Whitebread, Dr. Cesar

Barrientos, Jaime Garland, Hugo Pineda, Manuel Tay, Roberto Lou, Mario Penagos,

1986, Excreta Reuse (Guatemala), In: Zandstra, Ilse; Alex Redekopp, Reclamation of

nutrients, Water and energy from wastes: a review of selected IDRC-supported research,

International Development and Research Centre, Canada

Gosh, D., 1995, Integrated wetland system (IWS) for wastewater treatment and

recycling– for the poorer parts of the world with ample sunshine; basic manual, USAID,

New Delhi

Heinss, U., and Strauss, M. (1999). "Co-Treatment of Fecal Sludge and Wastewater in

Tropical Climates.”EAWAG,SANDEC Publications,

Heinss, U., Larmie, S. A., and Strauss, M. (1998). “Solids separation and pond systems

for the treatment of fecal sludge are in the tropics." Rep. No. SANDEC report 5/98,

EAW Switzerland,

Horan N, J (1990) Biological Wastewater treatment systems, Theory and operation, John

Wiley and sons. Ltd UK

http://www.eawag.ch/publication_e/e_index.html (February 5, 2005)

J.Jeffrey pierce, Ruth F.weiner, P.Aarne vesilind, Environmental Pollution and Control,

Butter Worth-Heinemann 1998 ISBN 0-7506-9899-3.


79

Karl Imhoff, W.j.Muller and D.K.B Thistlethywayte, Disposal of Sewage and other

water borne systems, London Butterworth’s 1971

Koottatep, T., Polprasert, C., Oanh,N.T.K., Suirnkil, N., Montangero, A.,Strauss, M.

(2003), Constructed Wetlands for Septage Treatment – Towards Effective faecal sludge

management. Paper presented at IWA 8th Int. Conference on Wetlands Systems for

Pollution Control, Arusha,Tanzania, September 15-19

Ligman, K, Hutzler, N and Boyle, W C (1974) ‘Household Wastewater

Characterization; Journal of the Environmental Engineering Division, American Society

of Civil Engineers, vol 100, no EE1, pp 201–213

Metcalf-Eddy (Fourth edition) 2003, Wastewater Engineering; Treatment and reuse, Mc

Graw-Hill, Inc.

Montangero, A., and Strauss, M. (2002). "Fecal Sludge Treatment." Swiss Federal

Institute for Environmental Science (EAWAG), SANDEC.

Montangero, A., Strauss, M. (eds) (2004), Faecal Sludge Treatment, Swiss Federal

Institute of Environmental Science and Technology (EAWAG)/SANDEC, Dubendorf,

Switzerland

NVA, Slibwijzer 1994, Treatment of faecal sludge, NVA publication.

SANDEC, 1997, Faecal sludge quantities and characteristics, unpublished.

Shrestha R R (1999) Application of Constructed Wetlands for Wastewater Treatment in

Nepal, Ph.D. Dissertation, Department of Sanitary Engineering and Water Pollution

Control, University of Agricultural Sciences Vienna, Austria

Van Hoven, D. (2004). “Septage in Jamaica: An Assessment of the Situation and an

Evaluation of Treatment Alternatives”, Report for the Ministry of Health.

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|APPENDIXES

80

APPENDIXES

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|Appendix 01: AVERAGE PHYSICAL CHARACTERISTICS OF WASTEWATER

OF SALASALA SYSTEM ALONG THE TREATMENT PLANT

81

Appendix 01: AVERAGE PHYSICAL CHARACTERISTICS OF WASTEWATER OF SALASALA SYSTEM ALONG THETREATMENT PLANT

Sample

Number

Temperature

(°c)

TDS

(mg/l)

PH Conductivity

(ms/cm)

Salinity

(‰)

Colour

(mg Pt-co/l)

Turbidity

(NTU)

Total

suspended

solid TSS,

( mg/l)

S 01 27.67± 12.44 1616.5 ± 744.96 6.6 ± 0.36 3.13 ± 0.49 1.5 ± 0.67 3175± 1431.08 1124.5±150.56 1325 ± 598.33

S 02 27.68± 12.43 1203.25 ± 565.19 6.73 ± 0.26 2.053 ±0.65 1.23 ± 0.56 2325 ±1071.45 725 ± 150.00 407.5 ± 182.29

S 03 28.15± 12.61 1220.25 ± 563.45 6.65 ± 0.31 2.12 ± 0.49 1.13 ± 0.51 2275 ±1035.37 825 ± 150.00 407.5 ± 182.70

S 04 28.27± 14.14 1167.25 ± 549.54 6.73 ± 0.35 2.41 ± 0.49 1.03 ± 0.46 900 ± 432.43 500 ± 81.65 251.5 ± 118.31

TBS

Standards 20-35 6.5-8.5 300 300 100

Key:

S01-Sample from inlet of the pond,

S02-Sample from middle of the pond,

S03-Sample from outlet of the pond or Inlet of the constructed wetland,

S 04-Sample from outlet of constructed wetland

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|Appendix 02: AVERAGE CHEMICAL CHARACTERISTICS OF WASTEWATER

OF SALASALA SYSTEM ALONG THE TREATMENT PLANT

82

Appendix 02: AVERAGE CHEMICAL CHARACTERISTICS OF WASTEWATER OFSALASALA SYSTEM ALONG THE TREATMENT PLANT

NH3-N (mg/l) PO4(mg/l)

Sample 01 223.33 ± 20.82 500 ± 0.00

Sample 02 151 ± 10.15 200 ± 86.60

Sample 03 155.33 ± 6.43 150 ± 86.60

Sample 04 129.67 ± 5.03 200 ± 86.60

TBS Standard 15 6

Key:





ARDHI UNIVERSITY Dissertation by Ulotu Gerald|Appendix 03: AVERAGE BIOLOGICAL CHARACTERISTICS OF

WASTEWATER OF SALASALA SYSTEM ALONG THE TREATMENT PLANT

83

Appendix 03: AVERAGE BIOLOGICAL CHARACTERISTICS OF WASTEWATER OFSALASALA SYSTEM ALONG THE TREATMENT PLANT

BOD5 (mg/l)

at 20 °C

COD (mg/l) Faecal coliform

(count/100ml)

Total coliform

(Count/100ml)

Sample 01 2253.33± 245.1 4506.67 ± 490.03 24,066,667 58,000,000

Sample 02 1040 ± 79.37 2080 ± 158.75 23,333,333 37,666,667

Sample 03 1015 ± 58.95 2030 ± 117.90 21,000,000 35,333,333

Sample 04 318.33 ± 17.56 636.67 ± 35.12 16,000,000 22,333,333

TBS standard 30 60 1000 10000

WHO

standards

25 50 1,000 -

Key:





ARDHI UNIVERSITY Dissertation by Ulotu Gerald|Appendix 04: GAS VOLUME IN mL OF SLUDGE STABILITY TEST FOR

FOURTEEN DAY DURATION

84

Appendix 04: GAS VOLUME IN mL OF SLUDGE STABILITY TEST FOR FOURTEEN DAY DURATION

SAMPLENAME

DAY01

DAY02

DAY03

DAY04

DAY05

DAY06

DAY07

DAY08

DAY09

DAY10

DAY11

DAY12

DAY13

DAY14

SubTotal

S1 55 110 130 70 80 70 50 40 40 38 38 35 38 36 830

S2 25 20 20 15 30 20 10 10 8 5 5 5 8 4 185

S3 70 60 50 50 50 50 50 45 30 20 25 15 15 10 540

S4 70 55 40 45 60 48 52 50 40 40 42 35 38 35 650

S5 75 65 30 25 20 32 35 5 2 2 1 1 1 0 294

S6 300 280 100 50 20 8 2 1.5 0 0 0 0 0 0 761.5

S7 100 80 50 10 10 50 3 30 20 20 22 22 15 15 447

S8 75 70 60 50 100 70 55 55 55 40 45 40 35 36 786

S9 90 75 65 60 80 70 70 70 68 60 60 55 55 50 928

Total 5421.5

Average 602.3889

SAMPLE NAME DESCRIPTION




S4 Water zone sludge sample from South side of the pond

S5 Water zone sludge sample from North side of the pond

S6 Sludge sample from middle point of the pond




ARDHI UNIVERSITY Dissertation by Ulotu Gerald|Appendix 05: SALASALA POND SLUDGE DEPTH AND VOLUME RESULTS

85

Appendix 05: SALASALA POND SLUDGE DEPTH AND VOLUME RESULTS

X,Y Z(m)Volume

(m3) X,Y Z (m)Volume



(m3)2,2 0.2 0.2 10,2 0.15 0.39 18,2 0.56 1.11 26,2 0.7 1.42,4 0.21 0.41 10,4 0.3 0.94 18,4 0.58 2.2 26,4 0.75 2.952,6 0.22 0.43 10,6 0.21 1 18,6 0.56 2.15 26,6 0.89 3.312,8 0.21 0.43 10,8 0.33 0.99 18,8 0.59 2.19 26,8 1 3.67

2,10 0.3 0.51 10,10 0.36 1.13 18,10 0.6 2.26 26,10 0.9 3.712,12 0.32 0.62 10,12 0.35 1.19 18,12 0.61 2.26 26,12 1 3.82,14 0.2 0.52 10,14 0.42 1.37 18,14 0.61 2.31 26,14 0.88 3.882,16 0.31 0.51 10,16 0.43 1.56 18,16 0.6 2.34 26,16 0.87 3.654,2 0.32 0.52 12,2 0.33 0.48 20,2 0.61 1.17 28,2 0.75 1.454,4 0.22 0.95 12,4 0.23 1.01 20,4 0.6 2.35 28,4 0.88 3.084,6 0.21 0.86 12,6 0.22 0.96 20,6 0.65 2.39 28,6 0.89 3.414,8 0.25 0.89 12,8 0.27 1.03 20,8 0.65 2.45 28,8 0.9 3.68

4,10 0.23 0.99 12,10 0.32 1.28 20,10 0.67 2.51 28,10 0.89 3.694,12 0.15 1 12,12 0.33 1.36 20,12 0.69 2.57 28,12 0.86 3.654,14 0.17 0.84 12,14 0.36 1.46 20,14 0.66 2.57 28,14 0.91 3.654,16 0.22 0.9 12,16 0.36 1.57 20,16 0.68 2.55 28,16 0.91 3.576,2 0.21 0.53 14,2 0.38 0.71 22,2 0.72 1.33 30,2 0.66 1.416,4 0.21 0.96 14,4 0.44 1.38 22,4 0.72 2.65 30,4 0.78 3.076,6 0.22 0.86 14,6 0.41 1.3 22,6 0.7 2.67 30,6 0.8 3.356,8 0.23 0.91 14,8 0.4 1.3 22,8 0.73 2.73 30,8 0.87 3.46

6,10 0.17 0.88 14,10 0.47 1.46 22,10 0.76 2.81 30,10 0.88 3.546,12 0.33 0.88 14,12 0.48 1.6 22,12 0.79 2.91 30,12 0.89 3.52 KEY6,14 0.34 0.99 14,14 0.54 1.71 22,14 0.8 2.94 30,14 0.9 3.56

X,Y-COORDINATESZ-SLUDGE DEPTH

6,16 0.33 1.06 14,16 0.53 1.79 22,16 0.81 2.95 30,16 0.9 3.628,2 0.24 0.45 16,2 0.55 0.93 24,2 0.7 1.42 32,2 0.55 1.218,4 0.25 0.91 16,4 0.51 1.88 24,4 0.8 2.94 32,4 0.59 2.588,6 0.24 0.92 16,6 0.5 1.86 24,6 0.87 3.09 32,6 0.8 2.978,8 0.21 0.9 16,8 0.54 1.85 24,8 0.91 3.21 32,8 0.86 3.33

8,10 0.23 0.84 16,10 0.53 1.94 24,10 0.9 3.3 32,10 0.9 3.51 NOTE8,12 0.25 0.98 16,12 0.52 2 24,12 1 3.45 32,12 0.93 3.6 All coordinates are in

meters (m)8,14 0.35 1.27 16,14 0.57 2.11 24,14 1 3.59 32,14 0.94 3.668,16 0.36 1.38 16,16 0.56 2.2 24,16 0.9 3.51 32,16 0.92 3.66

Total volume(m3) 252.52

ARDHI UNIVERSITY Dissertation by Ulotu Gerald|Appendix 06: RAW DATA OF PHYSICOCHEMICAL PARAMETERS FOR

WASTEWATER OF SALASALA FAECAL SLUDGE MANAGEMENT SYSTEM

86

Appendix 06: RAW DATA OF PHYSICOCHEMICAL PARAMETERS FORWASTEWATER OF SALASALA FAECAL SLUDGE MANAGEMENT SYSTEM

a) Physical parameters

1)Temperature

(°c)

TDS(mg/l

)PH

Conductivity(ms/cm)

Salinity(%)

Turbidity(NTU)

Totalsuspendedsolid TS,

(mg/l)

Colour(mg Pt-

co/l)

S 01 29.8 1918 6.9 3.85 1.4 1200 1400 3000

S 02 29.9 1422 7.1 2.78 1.2 600 410 2400

S 03 29 1426 7 2.8 1 900 400 2200

S 04 28.9 1374 7.1 2.74 1 600 300 700

2)Temperature

(°c)

TDS(mg/l

)PH

Conductivity(ms/cm)

Salinity(%)

Turbidity(NTU)


(mg/l)

Colour(mg Pt-

co/l)

S 01 26.8 1590 5.8. 2.78 1.6 998 1300 3400

S 02 27.4 1006 6.5 2.12 1.2 600 410 2700

S 03 27.2 1128 6.8 1.72 1.1 1000 430 2500

S 04 27..6 1300 6.9 2 1 500 270 1000



87

3)Temperature

(°c)TDS

(mg/l) PHConductivity

(ms/cm)Salinity

(%)Turbidity

(NTU)


(mg/l)

Colour(mgPt-

co/l)

S 01 27.1 1478 6.2 2.89 1.5 1000 1200 3300

S 02 27.2 1065 6.7 2.11 1.1 800 400 2000

S 03 27.5 1267 6.3 2.12 1.1 700 400 2000

S 04 27.9 995 6.3 1.98 1 400 203 1100

4)Temperature

(°c)TDS

(mg/l) PHConductivity

(ms/cm)Salinity

(%)Turbidity

(NTU)


(mg/l)

Colour(mgPt-

co/l)

S 01 27 1480 6.7 3 1.5 1300 1400 3000

S 02 25.9 1320 6.6 1.2 1.4 900 410 2200

S 03 28.9 1060 6.5 1.81 1.3 700 400 2400

S 04 28 1000 6.6 2.91 1.1 500 233 800

b) Chemical parameters

1)NH3-

N(mg/l)

PO4(mg/l) 2)NH3-

N(mg/l)

PO4(mg/l) 3)NH3-

N(mg/l)

PO4(mg/l)

Sample01

230 500Sample01

200 500Sample01

240 500

Sample02

160 250Sample02

140 100Sample02

153 250

Sample03

148 100Sample03

160 250Sample03

158 100

Sample04

135 250Sample04

125 100Sample04

129 250



88

c) Biological parameters

1) BOD5 (mg/l) at20 °C

COD(mg/l)


Total coliform(Count/100ml)

Sample01 2250 4500 25200000 57000000Sample02 1100 2200 22000000 35000000Sample03 950 1900 20000000 38000000Sample04 320 640 17000000 18000000

2)BOD5 (mg/l) at20 °C

COD(mg/l)




3)BOD5 (mg/l) at20 °C

COD(mg/l)




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Assessment and Improvement of SALASALA Private Decentralized fecal sludge Management System

Documents

sludge pond

sludge samples

sludge volume

mgl tbs standards

sludge depth

sludge treatment

mgl wheres tbs standards

ntu tbs standards