'Investigation of decentralised wastewater recycling for irrigation of public open space in urban villages – Development of a model for reliable management systems and improved protection of public health and the environment within the Perth Metropolitan Region' Shaun Jamieson B.Sc (Environmental Technology) Honours Thesis Supervised by Dr. Martin Anda Co-supervisor Prof. Goen Ho. School of Environmental Science, Murdoch University November 2006
103
Embed
'Investigation of decentralised wastewater recycling for ... · Perth must move towards closing the cycle of water. One method of doing this is by creating decentralised wastewater
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
'Investigation of decentralised wastewater recycling for
irrigation of public open space in urban villages – Development
of a model for reliable management systems and improved
protection of public health and the environment within the Perth
Metropolitan Region'
Shaun Jamieson B.Sc (Environmental Technology)
Honours Thesis
Supervised by Dr. Martin Anda
Co-supervisor Prof. Goen Ho.
School of Environmental Science, Murdoch University
November 2006
Declaration This thesis is presented to complete the requirements of a Bachelor of Science
(Environmental Science) with Honours.
I declare that the work compiled within this thesis is based on my own account of
research conducted at Murdoch University, Western Australia.
Shaun Jamieson July 05, 2006
iii
Papers Arising from this study A Technology Database for Onsite Wastewater Management Systems. Paper presented at “Turning Waste to Water” seminar in Denmark, Western Australia, December 2005. A Technology Database for Decentralised Wastewater Recycling Systems. Paper presented at the International Conference on Decentralised Water and Wastewater Systems Fremantle. Western Australia, July 2006.
iv
Abstract The incorporation of decentralised wastewater recycling systems on the ‘urban
village’ or ‘subdivision’ scale can play a major role in the move towards water
sensitive urban development. As well, this approach can potentially provide a range of
sustainable development benefits over conventional centralised sewerage systems.
While decentralised wastewater recycling can present many environmentally
sustainable benefits, the successful implementation of such system requires an
integrated consideration for four interrelated technical elements:
• Public health requirements;
• Environmental requirements;
• Appropriate technology selection; and
• Management system development.
A Technical Element Model (TEM) was developed that identifies each technical
element component, how they interconnect, and where they apply within the various
implementation process steps. The model is specifically characterised towards
decentralised wastewater recycling for irrigation of public open space in urban
villages of the Perth Metropolitan Region, however the fundamental components of
the model can be adapted to meet a range of wastewater recycling situations. The
TEM can potentially assist with the employment of this water and energy saving
approach, however, further development is required before a real life application.
v
Table of Contents Abstract .........................................................................................................................iv Table of Contents...........................................................................................................v List of Figures..............................................................................................................vii List of Tables ..............................................................................................................viii List of Abbreviations .....................................................................................................x Acknowledgments.........................................................................................................xi 1. Introduction................................................................................................................1
1.1 Background ..........................................................................................................1 1.2 Need for study......................................................................................................2 1.2 Research process, aims and objectives. ...............................................................2
1.2.1 Aim ...............................................................................................................3 1.2.2 Objective .......................................................................................................3 1.2.3 Research process...........................................................................................4
2. Literature Review.......................................................................................................5 2.1 Sustainable wastewater management...................................................................5 2.2Domestic wastewater ............................................................................................7
2.21 Sources and streams.......................................................................................7 2.2.3 Nutrients........................................................................................................9
2.4 Water management within the Perth Metropolitan Region ...............................12 2.4.1 Water use ....................................................................................................12 2.4.2 Wastewater management ............................................................................13 2.4.3 Nutrient issues.............................................................................................15 2.4.4 Policies, Regulations and Standards ...........................................................16
2.6 Summary ............................................................................................................17 3. Project Objectives and Methods ..............................................................................18
3.2 Methods..............................................................................................................22 3.2.1 Technical requirements...............................................................................22 3.2.2 Appropriate technology choice ...................................................................22 3.2.3 Decision support tool model .......................................................................23
4. Technical Requirements...........................................................................................24 4.1 Public health protection .....................................................................................24
4.2 Environmental Protection ..................................................................................29 4.2.2 Draft National Guidelines for Water Recycling .........................................32 4.2.3 Minimum setback distances........................................................................40 4.2.3 Water Quality Protection Notes ..................................................................40
4.3 Management systems .........................................................................................43 4.3.1 Risk management framework approach......................................................43 4.2.3.2 Nutrient Irrigation Management Plan ......................................................45
vi
4.4 System design and implementation process ......................................................46 5. Appropriate Technology Selection ..........................................................................49
5.1 General configuration ........................................................................................50 5.2 Scale of collection..............................................................................................50 5.3 Recycling system components...........................................................................52 5.4 Evaluation system ..............................................................................................53
6. Technical Elements Model ......................................................................................61 7. Discussion ................................................................................................................65
7.3 Further development ..........................................................................................69 8. Conclusion ...............................................................................................................72 References....................................................................................................................73 Appendix A – Fit for Purpose Guidelines for Recycled Water ...................................76 Appendix B – Management system elements explained (EPHC, 2005) .....................79 Appendix C – Treatment type descriptions .................................................................90 Appendix D – Evaluation criteria description .............................................................91
vii
List of Figures Figure 1 Various sources of household water including black, grey, brown and yellow,
going to deep sewerage (diagram modified from IETC, 2002) .............................8 Figure 2 Average single residential household water usage in Perth (source: WC,
2005) ....................................................................................................................13 Figure 3 Elements of the framework for management of recycled water quality and
use (EPHC, 2005) ................................................................................................45 Figure 4 A comparison of the ATU treatment types available on a cluster scale. (Note:
lower values areas are best). ................................................................................58 Figure 5 A comparison of the ATU treatment types available on a cluster scale. (Note:
lower values areas are best). ................................................................................59 Figure 6 The two employment phases of decentralised wastewater recycling system.
..............................................................................................................................61 Figure 7 The five steps of the implementation process and the interconnection with
the technical elements ..........................................................................................63 ure 8 The environmental requirements component of the model ................................64 Figure 9 The public health requirements component of the model ......................64
viii
List of Tables Table 1 Factors affecting the decision to select a decentralised or centralised
wastewater system (Ho, 2005, p16).......................................................................6 Table 2 Comparison of the characteristics of untreated black, grey, yellow, and brown
water (Source: Huber (2004) and DoH (2005)) .....................................................8 Table 3 The benefits and limitations of centralised sewerage networks in comparison
to decentralised systems.......................................................................................14 Table 4 A summary of two classes within the Fit for Purpose Guidelines for Water
Recycling that are applicable for wastewater recycling via POS irrigation ........26 Table 5 A revised version of the Fit for Purpose Guidelines including information
from the Draft National Guidelines for Water Recycling and to be used in the technical elements model.....................................................................................27
Table 6 A revised version of the Fit for Purpose Guidelines for Water Recycling for greywater to be used in the technical elements model.........................................28
Table 7 The indicative drainage classes specified in the ASNZS 1547, and the new drainage classes adopted in the technical elements model. .................................30
Table 8 The new maximum design irrigation rates for the technical elements model...............................................................................................................................31
Table 9 A list of key environmental hazards associated with domestic wastewater ..32 Table 10 Environmental factors, hazards and effects that need to be considered when
determining environmental risk. ..........................................................................33 Table 11 The minimum setback distances or ‘buffer zones’ to be applied in the
technical elements model.....................................................................................40 Table 12 Vulnerability to eutrophication of downstream surface water bodies and
vulnerability classes as specified by Department of Environment Water Quality Protection Notes...................................................................................................41
Table 13 The maximum inorganic nitrogen and phosphorus for the vulnerability categories as specified by Department of Environment Water Quality Protection Notes ....................................................................................................................41
Table 14 The five stages of a decentralised wastewater recycling implementation process (ASNZS 1547) ........................................................................................47
Table 15 The three available scales of decentralised wastewater recycling................51 Table 16 The general concept behind the scale of collection selection model ............51 Table 17 The various wastewater treatment type groups and there appropriateness for
village or cluster scale decentralised wastewater recycling in urban villages .....52 Table 18 The groups, categories and subcategories of the cataloguing system (A
description of each category and sub category is provided in Appendix C) .......52 Table 19 A brief description and associated measurement values used in the
evaluation scoring system (Appendix D).............................................................54 Table 20 An example of the scoring sheet used for the treatment type: Activated
Sludge (continuous aeration) on a cluster scale (Appendix E) ............................54 Table 21 The nutrient risk allocated to the four soil vulnerability categories (Table12).
..............................................................................................................................56 Table 22 The organic and nutrient impact evaluation scores for the different ATU
treatment types (Note: lower values are best)......................................................57 Table 23 The ATU treatment types selected for cluster scale application Note: the first
treatment type listed in each section is the first recommendation, and so on).....59
ix
Table 24 The ATU treatment types selected for village scale application Note: the first treatment type listed in each section is the first recommendation, and so on).....60
x
List of Abbreviations AS Activated sludge ATU Aerobic treatment unit BOD Biological oxygen demand DeWaTARS Decentralised Wastewater Treatment and Recycling Systems EDST Electronic decision support tool FB Fluidised Bed MBBR Moving bed bioreactor MBR Membrane bioreactor PF Percolating filter PMR Perth Metropolitan Region RBC Rotating biological contactor SAF Submerged aerated filter SS Suspended solids TN Total nitrogen TP Total phosphorus
xi
Acknowledgments I would like to thank my supervisors Dr. Martin Anda and Prof. Goen Ho who
provided a vast array of guidance and support throughout the duration of the thesis.
Thanks also to my sponsors, the Premiers Water Foundation and National Lifestyle
Villages. I would also like to give recognition to my colleagues at the Murdoch
University Environmental Technology Centre, who have offered me extensive
technical advice and personal encouragement.
My biggest acknowledgment goes to my wonderful family and partner Amy. You
guys have given me the strength to carry on through the toughest months of my life.
Amy you have been there by my side throughout the duration of my tertiary schooling
and your friendship and support has been invaluable. To my direct family Lyn, Ross,
Brayden, Rhys (dec.), and Tori – for you I have strived to achieve, thank you.
The Grantee appreciates the assistance provided by the Premier’s Water Foundation. The views expressed are not necessarily the views of the Government of Western Australia, nor the Premier’s Water Foundation.
Figure 1 Various sources of household water including black, grey, brown and yellow, going to deep sewerage (diagram modified from IETC, 2002)
Domestic wastewater can be divided into a number of separate streams (IETC,
2002). The most common separation includes ‘blackwater’ from the toilet/s and
‘greywater’ from all other household sources (Figure 2). The blackwater can be
further divided into urine only ‘yellow water’ or faeces only ‘brown water’
(Huber, 2004).
Table 2 Comparison of the characteristics of untreated black, grey, yellow, and brown water (Source: Huber (2004) and DoH (2005)) Type of wastewater BOD Total
Nitrogen Total
Phosphorus Total coliforms
Untreated sewage (combined sources)
100-500 (mg/L)
~35 (mg/L)
~10 (mg/L)
107-109 (MPN*/100mL)
Blackwater 59% 97% 90% High Yellow water 12% 87% 50% Very low Brown water 47% 10% 40% Very high
Greywater 41% 3% 10% Medium * MPN – most probable number
The system requires over 550 pump stations (WC, 2003) to distribute the sewage to 3
major treatment plants, including Woodman Point, Subiaco and Beenyup, as well as
several smaller plants (EPA, 2005). Currently only 3.3% (~3.4GL) of the total
wastewater is being recycled per year, with the remaining 100GL discharged via
ocean outfall (EPA, 2005). Due to the large and complex nature of this wastewater
conveyance network continual overflow events are evident. On average there are 11
wastewater overflow events per year in Perth, releasing volumes as high as 15 mega
litres (15 million litres) per spill (WC, 2003).
Table 3 The benefits and limitations of centralised sewerage networks in comparison to decentralised systems
Benefits Limitations Historically provided public health
benefits and a convenient household service.
Lower capital and operating cost of treatment systems due to economies of scale.
Easier management than can be supplied by one service provider.
Prevents nutrients and other contaminants entering superficial aquifers and wetlands within the Swan Coastal Plain
Currently conveys nutrients and other contaminants into the ocean where they can potentially pose less direct risk to public health and the environment.
The widespread network helps to remove onsite septic tanks systems that have associated environmental impacts
Many parts of the system rely on high levels of water use to provide adequate conveyance.
Diseconomies of scale present due to the need for large and extensive pipe work and deep excavations, especially with sandy nature of Swan Coastal Plain making deep excavation more difficult.
Energy intensive process just to achieve wastewater disposal (includes energy required for pumping and treatment)
Recycling of wastewater is difficult and costly due to distribution of reclaimed effluent requirements.
Combining of domestic and industrial wastewater makes recycling of effluent less desirable due to introduction of industrial contaminants.
A relatively fresh and treated wastewater stream is combined with saline ocean water.
Large raw sewerage spills are probable due to scale and complexity
Replacement of piping network costly and disruptive to public.
Potential environmental impacts associated with point source disposal into the ocean and spill events
Table 4 A summary of two classes within the Fit for Purpose Guidelines for Water Recycling that are applicable for wastewater recycling via POS irrigation Class Recycled Water Quality
Objectives Treatment Process Uses
A
< 10 E.coli org/100 mL Turbidity < 2 NTU6 < 10 / 5 mg/L BOD / SS pH 6 – 9 7 1 mg/L Cl2 residual (or equivalent disinfection) <10 E.coli per 100 mL; <1 helminth per litre; < 1 protozoa per 50 litres; < 1 virus per 50 litres.
Secondary
Filtration
Disinfection
Urban (non-potable): with uncontrolled public access
C
<1000 E.coli org/100
mL pH 6 – 9 7 < 20 / 30 mg/L BOD /
SS
Secondary +
pathogen reduction
Urban (non-potable): with controlled public access
Application of the FPGRW for public open space irrigation is summarised in Table 4,
which does not include Class B as it is not specified as being applicable for Urban
(non-potable) uses (Appendix A). However, the DNGWR study indicates that Class B
should be preferred over Class C, as it poses less public health risk. Also, it is likely
that secondary treatment combined with conventional disinfection, (e.g. chlorination,
UV, etc.) will produce Class B water, and Class C largely represents pathogen
reduction by die-off achieved by long detention times in lagoons or wetlands (i.e.
>30days for secondary treated water or >60days for primary treated effluent).
Treatment systems that require high hydraulic retention times to achieve pathogen
die-off are not likely to be suitable within urban villages of a metropolitan region such
as Perth, mainly due to high land area requirements and other aesthetic challenges.
Therefore, other methods that rely on much shorter hydraulic retention times are
required along with a form of disinfection, which according to the DNGWR is likely
to achieve an effluent that complies with Class B. While Class B is not directly
required by the Department of Health guidelines; achieving treated effluent of this
quality will present less risk to public health.
The applicable parts of the FPGWR can be combined with the additional information
provided in the DNGWR to produce a more informative description of the available
water quality classes (Table 5, below). This can act as a more informative framework
to be used in the overall model, while also complying with the Department of Health
specified guidelines.
Table 5 A revised version of the Fit for Purpose Guidelines including information from the Draft National Guidelines for Water Recycling and to be used in the technical elements model. Class Irrigation Use Treatment Process Disinfection
Objectives Likely Disinfection
Requirements
A
Urban (non-potable): with uncontrolled public access - Uncontrolled Spray Irrigation
Secondary +
Advanced filtrat’n +
Disinfection
< 10 E.coli org/100 mL
Chlorine residual ~ >60mg.min/L;
UV light ~ 100mJ/cm2;
Or equivalent
B/C
Urban (non-potable): with controlled public access - Drip irrigation; or - Controlled spray irrigation*
Secondary +
Disinfection
<100 E.coli per 100 mL preferable <1000 E.coli per 100 mL acceptable
Chlorine residual ~ >15mg.min/L; Or equivalent
*Includes a combination of the following: No public access during irrigation Exclusion periods (e.g. no use until 1-4 hours after irrigation) 25-30m buffer zones to nearest point of public access Spray drift control
Surface waters Directly toxic to plants Toxic to aquatic biota
Nitrogen Soils Soils Surface water Groundwater
Nutrient imbalance and pest and disease in plants Eutrophication of soils and effects on terrestrial biota Eutrophication Contamination
Phosphorous Soils Surface waters
Eutrophication of soils and toxic effects on phosphorus sensitive terrestrial biota (Native plants) Eutrophication
Salinity Infrastructure Soils Soils Groundwater Surface water
Rising damp, corrosion, secondary salinity Plant stress due to osmotic affects of soil salinity May increase release of cadmium from soil Increase salinity Increase salinity
The area to be irrigated with treated wastewater should be setback from various items
to ensure environmental performance, which can also be termed buffering distance or
buffer zones. The Code of Practice for the Reuse of Greywater in Western Australia
stipulates a range of guideline distances for greywater irrigation. As the distances are
for greywater that has been treated to an equivalent class B/C or better (Table 6), it
can be assumed that these figures can also be applied to blackwater treated to a class
B/C or better. The distances set by the Code of Practice are summarised in Table 4.7
(below).
Table 11 The minimum setback distances or ‘buffer zones’ to be applied in the technical elements model.
Item Drip irrigation (m)
Spray irrigation (m)
Closed fence boundaries 0.3 0.5 Open boundaries (e.g. open fence or no fence)
0.5 1.2
Buildings 0.5 0.5 Paths, drives, carports, etc. 0.3 1.8 Sub-soil drains 3.0 3.0 Bores (private) 30 30 Public drinking water source * 100 100 Wetlands and water dependant ecosystems where the PRI is <5
100 100
* Includes Drinking Water Source Protection Areas
4.2.3 Water Quality Protection Notes
4.2.3.1 Irrigation Protection notes
In order to obtain the target criteria concentrations for nitrogen and phosphorus the
Water Quality Protection Notes – Irrigation with Nutrient Rich Wastewater released
by the Department of Environment were reviewed (DoE, 2004). The
recommendations of the document are summarised in Table 12 and 13 below.
Table 12 Vulnerability to eutrophication of downstream surface water bodies and vulnerability classes as specified by Department of Environment Water Quality Protection Notes
Characteristics of the irrigated soil
Vulnerability to eutrophication of
downstream surface waters
(within 1 kilometre)
Vulnerability Category e
Significant b A Coarse grained soils a e.g. sands, or gravels. Low c B
Significant b C Fine grained soils (PRI d above 10) e.g. loam, clays, peat-rich sediment Low c D Notes: a. Specific restrictions may apply where near-surface soil conditions are likely to lead to rapid water movement without achieving significant immobilisation of entrained contaminants (e.g. in karstic limestone, coarse gravels or fractured rock). b. Significant eutrophication risk applies to translucent inland waters, with nutrient leaching pressures from catchment land use resulting in occasional algal blooms; or where warm season dissolved inorganic nitrogen concentrations exceed 1 mg/L and filterable reactive phosphorus (ortho-phosphate) concentrations exceed 0.1 mg/L in the water body. c. Low eutrophication risk applies to highly coloured waters, those with rarely observed algal blooms (less than 5000 cells/mL), having low nutrient pressure from land use and those with warm season inorganic nitrogen concentrations of less than 0.5 mg/L and filterable reactive phosphorus less than 0.05 mg/L. d. PRI means Phosphorus Retention Index, a scientifically determined measure of the phosphorus holding capacity of soils between the ground surface and base of the vegetation root zone e. These vulnerability categories are applied to nutrient application rate recommendations in Table 13. Table 13 The maximum inorganic nitrogen and phosphorus for the vulnerability categories as specified by Department of Environment Water Quality Protection Notes
Maximum inorganic nitrogen (TN)
Maximum inorganic phosphorus (TP)
Vulnerability Category
Application rate (kilograms /
hectare / year)
Equivalent water concentration (mg/ litre) a
Application rate (kilograms /
hectare / year)
Equivalent water concentration (mg/ litre) a
A 140 9 10 0.6 B 180 11 20 1.2 C 300 19 50 3.1 D 480 30 120 7.5
Notes: a. The N and P concentrations are based on an average of 50 mm (500 kilolitres/ ha) of water applied per week for 32 weeks/year, and no additional nutrient addition to the land (including animal manure). For other irrigation regimes, equivalent water concentration rates should be calculated on a pro-rata basis. b. Application rates are based on quantities of plant-available N and P (as N as ammonia & nitrate, and P as ortho-phosphate) to promote healthy vegetation growth that are matched to the growth cycle of the irrigated plant species. For materials that require micro-biological decomposition to release plant-available nutrients (e.g. decay of green-waste), the local conditions will need to be factored into calculations (i,e. time, moisture, warmth, available oxygen and absence of toxins).
It should be noted that the figures provided in Table 13 are recommended nutrient
(nitrogen and phosphorus) application criteria in irrigated waters, based no additional
measures being taken to minimise contaminant leeching. The figures are based on
50mm per week application rate for 32 weeks of the year. Many large scale
wastewater irrigation systems will require irrigation for 52 weeks of the year, unless
design layout or geographic features it may be preferable to implement two or
more cluster systems rather than one village system. Therefore this is
incorporated into the appropriate technology choice investigation. As lot scale
collection of the wastewater is not suitable for public open space irrigation, it
will not be considered in this investigation.
5.3 Recycling system components
Following an extensive review of the all the available wastewater treatment
technologies it was determined that aerobic treatment units (ATUs) were the
only available wastewater recycling technology group suitable for village or
cluster scale collection and recycling of domestic wastewater in urban areas.
This is explained in Table 17, below.
Table 17 The various wastewater treatment type groups and there appropriateness for village or cluster scale decentralised wastewater recycling in urban villages
Group Appropriate (yes or no)
Reasoning
1. Aerobic Treatment Units Yes - Employs biological treatment processes that are simple and have been applied successfully for nearly 100years. - Small footprint required - Can easily be designed to achieve good nutrient removal
2. Infiltration Trenches No - Generally only used for small scale applications - Has limited wastewater reuse
3. Composting Systems No - Generally only for small scale applications 4. Ponds and Wetlands No - High footprint (land requirement) and aesthetics is often
an issue in urban developments 5. Anaerobic Systems No - Used to harvest biogas for energy
- Not suitable for relatively diluted wastewater typical of urban domestic situations
6. Physico-chemical Systems No - Very small footprint but minimal ammonium oxidation and total nitrogen removal
7. Greywater Treatment Systems No - Generally only for small scale applications, otherwise similar to ATUs
Table 18 The groups, categories and subcategories of the cataloguing system (A description of each category and sub category is provided in Appendix C)
Group Category Subcategory 1.0 Aerobic Treatment Units 1.1 Suspended growth 1.1a Activated sludge (continuous aeration) 1.1b Activated sludge (intermittent aeration)
measures that are commonly required in the establishment of a wastewater recycling
system. These were determined by assessing a number of case studies for the most
commonly considered treatment system characteristics and explained in Table 19
(below).
Table 19 A brief description and associated measurement values used in the evaluation scoring system (Appendix D)
Evaluation criteria
Description Measurement value
Organic Biological oxygen demand and suspended solids (mg/L) in the treatment system effluent.
BODmg/L / SSmg/L
Percentage ammonia removal by the treatment system
NH4 (% removal)
Percentage total nitrogen removal by the treatment system
TN (% removal)
Nutrient
Percentage total phosphorus removal by the treatment system
TP (% removal)
Energy use Kilowatt hours used per kilolitre of water treated
kWh/kL
Capital cost Capital cost ($AU.) per kilolitre per day rated treatment capacity
$/kL/day
Management cost Yearly management cost ($AU.) per inhabitant
$/inhab/year
Footprint Footprint (land area required) in m2 per inhabitant
m2/inhab
Sludge Liquid sludge required to be treated/disposed of per year in litres per inhabitant
L/inhab.year
The evaluation system comprises of a numbering matrix that provides a score between
zero and ten for a range of evaluation criteria (Table 20, below). Low scores are better
than high scores (i.e. the poorest score is 10). The scores are linked with estimated
real values for that criterion, illustrated in the scoring key of the evaluation system
spreadsheet (Table 20 and Appendix E).
Table 20 An example of the scoring sheet used for the treatment type: Activated Sludge (continuous aeration) on a cluster scale (Appendix E) Evaluation criteria Description Value Score
Table 22 The organic and nutrient impact evaluation scores for the different ATU treatment types (Note: lower values are best) 1.1a 1.1b 1.1c 1.2a 1.2b 1.2c 1.2d 1.3a 1.3b 1.3c
Organic 5 5 3 5 5 4 4 5 4 5
Nutrient 5 4 3 6 5 5 5 5 6 5
Each ATU treatment type had the same individual organic and nutrient
performance scores for cluster and village applications (Table 22). However, the
other evaluation criteria varied between different scales of application. As a
result, there are different recommended treatment types for cluster and village
MBBR is the next best followed by 1.2b – SAF (intermittent aeration), due to the low
footprint and energy use (Figure 4).
Table 23 The ATU treatment types selected for cluster scale application Note: the first treatment type listed in each section is the first recommendation, and so on)
Eight out of the ten ATU subcategories are available for village scale application.
Energy use, footprint and sludge production are an important evaluation criteria as
they tend to become more significant for large scale systems. The five standout
technologies include 1.1c MBR, 1.2b SAF, 1.2b MBBR, 1.3a PF (septic) and 1.3c
RBC.
Table 24 The ATU treatment types selected for village scale application Note: the first treatment type listed in each section is the first recommendation, and so on)
References Anda, M. (1997). Technology Choice and Sustainable Development. Proceeding of the workshop on adopting, applying and operating environmentally sound technologies for domestic and industrial wastewater treatment for the wider Caribbean Region. UNEP International Environmental Technology Centre. Osaka/Shiga, 1998. Asano, T. (1998). Wastewater Reclamation and Reuse. Water Quality Management Library – Volume 10. Technomic Publishing Company. Lancaster, USA. Berti, M.L., Bari, M.A., Charles, S.P. and Hauck, E.J. (2004). Climate Change, Catchment Runoff and Risks to Water Supply in the South-West of Western Australia, Department of Environment, Government of Western Australia. Cameron, C. (2005). Centralised Verses Decentralised Sewage. Australian Water Association Water Journal, March 2005. Cheremisinoff, N.P. (2002). Handbook of Water and Wastewater Treatment Technologies. Butterworth Heinemann. Melbourne. Clark, R. (1997). Optimum scale for urban water systems. Report 5 in the water sustainability in urban areas series. Water Resources Group. Dept. of Environment and Natural Resources. SA. Department of Environment (DoE). (2004). Water Quality Protection Note – Irrigation with Nutrient-rich wastewater. Western Australia, Feburary 2004. Department of Health (DoH). (2005). Code of Practice for the Reuse of Greywater in Western Australia. Water Corporation, Department of Environment and Department of Health January 2005. Available at www.health.wa.gov.au. Environmental Protection Agency (EPA). (2005). Strategic Advice on Managed Aquifer Recharge using Treated Wastewater on the Swan Coastal Plain. Section 16(e) report and recommendations of the Environmental Protection Authority. Perth, Western Australia. Bulletin 1199, October 2005. Environmental Protection and Heritage Council (EPHC). (2005). Draft National Guidelines for Water Recycling – Managing Health and Environmental Risks. October, 2005. Fane, S.A., Ashbolt, N.J. and White, S.B. (2002). Decentralised urban water reuse: the implications of system scale for cost and pathogen risk. Water Science and technology. 46(6-7):281-8. Faust, S.D. and Aly, O.M. (1998). Chemistry of Water Treatment. 2nd Ed. Ann Arbor Press. Michigan.
Forster, C. (2003). Wastewater Treatment and Technology. Thomas Telford Publishing. London. GHD Pty. Ltd. (2005). Water Corporation: Non-potable Water Use – Guidelines for developers and their consultants. September, 2005. Government of Western Australia (GoWA). (2003). A State Water Strategy for Western Australia. Perth, Western Australia. Gray, N. (1999). Water Technology – An Introduction fro Environmental Scientists and Engineers. Arnold. Sydney. Gunn, I. (1997). Achieving sustainable use of on-site domestic wastewater systems. UNEP Environmental Technology for Wastewater Management – Conference Papers. International Regional Conference, December 1997. Hellstrom, D. and Jonsson, L. (2005). Evaluation of small wastewater treatment systems. Water Science Technology: Small Water and Wastewater Treatment Systems V. 48 (11-12): 61-68. Ho, G. (2005). Technology for sustainability: the role of onsite, small, and community scale technology. Water Science Technology: Onsite Wastewater Treatment, Recycling and Small Water and Wastewater Systems. 51 (10): 29-38. Ho, G. and Anda, M. (2004). Centralised versus decentralised wastewater systems in an urban context: the sustainability dimension. Summary paper from the Leading Edge Conference on Sustainability in Water-Limited Environments 2004. Huber (2004). DeSa/R – Means to Achieving the Millennium Goal for Sanitation. DeSa/R-Synoposium Berching / Opf. 14th July 2004. International Environmental Technology Centre (IETC). (2002). Environmentally Sound Technologies for Wastewater and Stormwater Management – An International Source Book. Technical Publication Series [15]. IWA Publishing Osaka/Shiga, 2002.
Metcalf and Eddy. (2004). Wastewater Engineering – Treatment Disposal Reuse. Third edition, McGraw Hell international editions, Civil Engineering Series.
Newsome, D. (1998). Soils and Environmental Science. School of Environmental Science. Murdoch University. Rule, H., and Oliver, J. (1997). Neighbourhood Wastewater Treatment Plants are Cheaper: Fact or Fiction. UNEP Environmental Technology for Wastewater Management – Conference Papers. International Regional Conference, December 1997.
Water and Rivers Commission (WRC). (2002). Draft State Water Conservation Strategy for Western Australia, Water and Rivers Commission and Office of Water Regulation. Perth, Australia. Water Corporation (WC). (2003). Wastewater Overflows in the Perth Metropolitan Area to June 2003. Water Corporation of Western Australia. Perth, Australia. Water Corporation (WC). (2005). Our water sources. www.watercorporation.com.au/dams/dams_storage.cfm?rootparent=ourwatersources. Accessed: 5-4-2005. Western Australian Government (WAGov). (1996). Government Sewage Policy. Perth Metropolitan Region, 1996. White, S. and Turner. A. (2003). The Role of Effluent Reuse In Sustainable Urban Water Systems: Untapped Opportunities. National Water Recycling in
<1 E.coli per 100 mL; <1 helminth per litre; < 1 protozoa per 50 litres; < 1 virus per 50 litres. <2-10mg/L nitrogen
Secondary
Filtration
Disinfection
Advanced treatment
Indirect Potable Reuse Aquifer Recharge
A
< 10 E.coli org/100 mL Turbidity < 2 NTU6 < 10 / 5 mg/L BOD / SS pH 6 – 9 7 1 mg/L Cl2 residual (or equivalent disinfection)
<10 E.coli per 100 mL; <1 helminth per litre; < 1 protozoa per 50 litres; < 1 virus per 50 litres.
Secondary
Filtration
Disinfection
Urban (non-potable): with uncontrolled public access Agricultural: eg human food crops consumed raw Industrial: open systems with worker exposure potential
B
<100 E.coli org/100 mL pH 6 – 97 < 20 / 30 mg/L BOD / SS
Secondary +
pathogen reduction
Agricultural: eg dairy cattle grazing Industrial: eg washdown water
C
<1000 E.coli org/100 mL pH 6 – 97 < 20 / 30 mg/L BOD / SS
Secondary +
pathogen reduction
Urban (non-potable): with controlled public access Agricultural: eg human food crops cooked/processed, grazing/fodder for livestock Industrial: systems with no potential worker exposure
Secondary crops including instant turf, woodlots, flowers
* Table adapted from Victorian EPA guidelines 1. Unless otherwise noted, recommended quality limits apply to the recycled water at the point of discharge from the WWTP 2. Secondary Treatment processes include activated sludge processes, trickling filters, rotating biological contractors, and may include stabilization ponds. 3. Filtration means the passing of wastewater through natural undisturbed soils or filter media such as sand and/or anthracite, filter cloth, or the passing of wastewater through micro-filters or other membrane processes. 4. Disinfection means the destruction, inactivation, or removal or pathogenic microorganisms by chemical, physical, or biological means. 5. Advanced wastewater treatment processes include chemical clarification, carbon adsorption, reverse osmosis and other membrane processes, air stripping, ultrafiltration, and ion exchange. 6. Turbidity limit is a 24-hour median value measured pre-disinfection. The maximum value is five NTU. 7. pH range is 90th percentile. A higher upper pH limit for lagoon-based systems with algal growth may be appropriate, provided it will not be detrimental to receiving soils and disinfection efficacy is maintained. 8. Chlorine residual limit of greater than one milligram per litre after 30 minutes (or equivalent pathogen reduction level) is suggested where there is a significant risk of human contact or where recycled water will be within distribution systems for prolonged periods. 9. Helminth reduction is either detention in a pondage system for greater than or equal to 30 days, or by a DOH approved disinfection system (for example, sand or membrane filtration). 10. Where Class C or D is via treatment lagoons, although design limits of 20 milligrams per litre BOD and 30 milligrams per litre SS apply, only BOD is used for ongoing confirmation of plant performance. A correlation between process performance and BOD / filtered BOD should be established and in the event of an algal bloom, the filtered BOD should be less than 20 milligrams per litre.
Appendix B – Management system elements explained (EPHC, 2005) Element 1: Commitment to responsible use and management of recycled water Component Action Notes Responsible use of recycled water
• Involve agencies with responsibilities and expertise in protection of public and environmental health • Ensure that design, management and regulation of recycled water schemes is undertaken by agencies and operators with sufficient expertise
e.g. Dept. of Health and Dept. of Environment
Regulatory and formal requirements
• Identify and document all relevant regulatory and formal requirements • Identify governance of recycled water schemes • Ensure responsibilities are understood and communicated to employees • Review requirements periodically to reflect any changes
Regulatory and formal requirements may include: • WA and local government legislation and regulations • Operating licences and agreements • Recycled water use agreements and contracts • Agreed levels of service • Memoranda of understanding • Industry standards and codes of practice.
Partnerships and engagement of stakeholders (including the public)
• Identify all agencies with responsibilities for water resources and use of recycled water; regularly update the list of relevant agencies • Establish partnerships with agencies or organisations as necessary or where this will support the effective management of recycled water schemes • Identify all stakeholders (including the public) affecting, or affected by, decisions or activities related to the use of recycled water. • Engage users of recycled water; ensure responsibilities are identified and understood • Develop appropriate mechanisms and documentation for stakeholder commitment and involvement
Examples of agencies that may be involved include: • Health and environment protection authorities • Catchment and water resource management agencies • Primary industry agencies • Local government and planning authorities • Non-government organisations • Community-based groups • Industry associations • Construction industry representatives. Private organisations or companies may include: • Operators of recycled water distribution systems • Owners or managers of apartment buildings • Maintenance contractors who service recycled water treatment systems, including on-site systems • End users of recycled water (eg residents, farmers, councils).
• Develop a recycled water policy, endorsed by senior managers, to be implemented within an organisation or by participating agencies • Ensure that the policy is visible and is communicated, understood and implemented by employees and contractors
Example of policy for recycled water supplier is given in DNGWR (2005), pg 18.
Element 2: Assessment of the recycled system Component Action Notes Intended uses and source of recycled water
• Identify source of water • Identify intended uses and receiving environments, endpoints and effects • Consider inadvertent or unauthorised use
Explained in more detail in section in 4.2 Sources include sewage or greywater • Characteristics and proximity of receiving waters (surface water and groundwater) • Characteristics of soils at the point of application (ie receiving environments) • Site hydrology (groundwater, soil permeability, drainage) • The type of crops or plants to be irrigated (ie endpoints) • Application rates • On-site storages • Climatic conditions and evapotranspiration rates • Characteristics and proximity of sensitive or protected ecosystems • Quantities required, time of application, spatial variability of application across a district or catchment.
Recycled water system analysis
• Assemble pertinent information and document key characteristics of the recycled water system to be considered • Assemble a team with appropriate knowledge and expertise • Construct a flow diagram of the recycled water system from the source to the application or receiving environments
• Periodically review the recycled water system analysis
Assessment of water quality data
• Assemble historical data about sewage, grey water or stormwater quality, as well as data from treatment plants and of recycled water supplied to users; identify gaps and assess reliability of data • Assess data (using tools such as control charts and trends analysis), to identify trends and potential problems
Hazard identification and risk assessment
• Define the approach to hazard identification and risk assessment, considering both public and ecological health • Periodically review and update the hazard identification and risk assessment to incorporate any changes • Identify and document hazards and hazardous events for each component of the recycled water system • Estimate the level of risk for each identified hazard or hazardous event • Consider inadvertent and unauthorised use or discharge • Determine significant risks and document priorities for risk management • Evaluate the major sources of uncertainty associated with each hazard and hazardous event and consider actions to reduce uncertainty
The guidelines provided in section 4.1 can be used as a guideline for public health risk management. Section 4.2 provides a general guideline for environmental health risk management. A preliminary risk assessment should still be carried to accurately identify the hazards and associated risks. If unique or special hazards are identified or if the proposed recycling scheme includes unique or special aspects (not detailed in section 4.1 or 4.2) – then a detailed risk assessment should be carried out as per the DNGWR (2005).
Element 3: Preventative measures for recycled water management Component Action Notes Preventative measures and multiple barriers
• Identify existing preventive measures system-wide for each significant hazard or hazardous event, and estimate the residual risk • Identify alternative or additional preventive measures that are required to ensure risks are reduced to acceptable levels • Document the preventive measures and strategies, addressing each significant risk
Examples of preventive measures for recycled water systems - Water source protection (i.e. what goes into the sewage or greywater) - Water treatment (i.e. primary, secondary, tertiary) - Storage/treatment (i.e. lagoons, wetlands, infiltration etc.) - Protection and maintenance (i.e. buffer zones) - Restrictions on distribution system (i.e. site selection)
- Users of recycled water (i.e. cross connection controls)
Critical control points
• Assess preventive measures throughout the recycled water system to identify critical control points • Establish mechanisms for operational control • Document the critical control points, critical limits and target criteria
Critical control points require: - Operational parameters that can be measured. - Operational parameters that can be monitored frequently to reveal failures etc. - Procedures for corrective action For mechanisms for operational control consider: - Critical limits - Target criteria
Element 4: Operational procedures and process control Component Action Notes Operational procedures
• Identify procedures required for all processes and activities applied within the recycled water system • Document all procedures and compile into an operations manual
Operational monitoring
• Develop monitoring protocols for operational performance of the recycled water supply system, including the selection of operational parameters and criteria, and the routine analysis of results • Document monitoring protocols into an operational monitoring plan
Corrective action
• Establish and document procedures for corrective action to control excursions in operational parameters • Establish rapid communication systems to deal with unexpected events
Examples of process-control programs include: • Descriptions of all preventive measures and their functions • Documentation of effective operational procedures, including identification of responsibilities and authorities • Establishment of a monitoring protocol for operational performance, including selection of operational parameters such as target criterion and critical limits, and the routine review of data • Establishment of corrective actions to control excursions in operational parameters • Requirements for use and maintenance of suitable equipment • Requirements for use of approved materials and chemicals in contact with recycled water • Establishment of procedures for restricted end uses
• Ensure that equipment performs adequately and provides sufficient flexibility and process control • Establish a program for regular inspection and maintenance of all equipment, including monitoring equipment
Materials and chemicals
• Ensure that only approved materials and chemicals are used • Establish documented procedures for evaluating chemicals, materials and suppliers
• Establishment of procedures for activities undertaken by users of recycled water at application sites (particularly when end-use preventive measures are relied on to minimise the risk to acceptable levels).
Element 5: Verification of recycled water quality and environmental sustainability Component Action Notes Recycled water quality monitoring
• Determine the characteristics to be monitored • Determine the points at which monitoring will be undertaken • Determine the frequency of monitoring
Key characteristics to be monitored for verification include: • Microbial indicator organisms • Salinity, sodicity, sodium, chloride, boron, chlorine disinfection residuals, nitrogen and phosphorus • Any health-related characteristic that can be reasonably expected to exceed the guideline value, even if occasionally • Any characteristic of relevance to end use or discharge of the recycled water, which can be reasonably expected to exceed the guideline value, even if occasionally.
Application site and receiving environment monitoring
• Determine the characteristics to be monitored and the points at which monitoring will be undertaken
Areas requiring monitoring could include: • Soil chemistry and physical properties (eg salinisation, dispersion, structural stability) • Plants, terrestrial and aquatic biota • Groundwater and surface water quality and quantity (levels) • Infrastructure • Air.
• Establish and document a sampling plan for each characteristic, including the location and frequency of sampling, ensuring that monitoring data is representative and reliable
Recycled water user satisfaction
• Establish a recycled water user complaint and response program, including appropriate training of employees
Short-term evaluation of results
• Establish procedures for the short-term review of monitoring data and recycled water user satisfaction • Develop reporting mechanisms internally, and externally, where required
Short-term performance evaluation involves reviewing monitoring data and recycled water user satisfaction to verify that: • The quality of water supplied to application or receiving environments conforms to established targets and meets user expectations • The quality of receiving environments complies with approval conditions.
Corrective action
• Establish and document procedures for corrective action in response to non-conformance or recycled water user feedback • Establish rapid communication systems to deal with unexpected events
Element 6: Management of incidents and emergencies Component Action Notes Communication
• Define communication protocols with the involvement of relevant agencies and prepare a contact list of key people, agencies and stakeholders • Develop a public and media communications strategy
Incident and emergency response protocols
• Define potential incidents and emergencies and document procedures and response plans with the involvement of relevant agencies • Train employees and regularly test emergency response plans • Investigate any incidents or emergencies and revise protocols as necessary
Potential hazards and events that can lead to emergency situations include: • Non-conformance with critical limits, guideline values and other requirements • Accidents that increase levels of contaminants or cause failure of treatment systems (eg spills in catchments, illegal discharges into collection systems, incorrect dosing of chemicals) • Equipment breakdown and mechanical failure • Prolonged power outages • Extreme weather events (eg flash flooding, cyclones)
• Natural disasters (eg fire, earthquakes, lightning damage to electrical equipment) • Human actions (eg serious error, sabotage, strikes) • Outbreaks of illness leading to increased pathogen challenges on treatment systems • Cyanobacterial blooms in storages or waterways • Kills of fish or other aquatic life • Crops destroyed by irrigation with recycled water.
Element 7: Employee awareness and training Component Action Notes Employee awareness and involvement
• Develop mechanisms and communication procedures to increase employees’ awareness of and participation in recycled water quality management
End users should be made aware of the importance of end-use restriction barriers. As a minimum, all end users should be aware of: • Restrictions on use of recycled water • Management requirements that are essential to ensure the sustainable use of recycled water • Any practice that will threaten human or environmental health.
Employee training
• Ensure that employees, including contractors, maintain the appropriate experience and qualifications • Identify training needs and ensure resources are available to support training programs • Document training and maintain records of all employee training
Component Action Notes Recycled water user and community consultation
• Assess requirements for effective involvement of recycled water users and community • Develop a comprehensive strategy for consultation
Communication and education
• Develop an active two-way communication program to inform recycled water users and promote awareness of recycled water quality issues • Provide information on impacts of unauthorised use • Provide information on the benefits of recycled water use
Communication with the public is essential. Communication can help recycled water users to understand and contribute to decisions about services provided by a recycled water supply. A thorough understanding of the diversity of views held by individuals in the community is necessary to satisfy community expectations.
Element 9: Validation, research and development Component Action Notes Validation of processes
• Validate processes and procedures to ensure they control hazards effectively • Revalidate processes periodically or when variations in conditions occur
Design of equipment
• Validate the selection and design of new equipment and infrastructure to ensure continuing reliability
Investigative studies and research monitoring
• Establish programs to increase understanding of the recycled water supply system, and use this information to improve management of the recycled water supply system
Applied research and development could focus on areas such as: • Increasing understanding of sources and potential hazards • Investigating improvements, new processes, emerging water quality issues and new analytical methods • Validation of operational effectiveness of new products and processes • Increasing understanding of the relationship between public health and environmental outcomes and recycled water quality • Assessing quality of products grown using recycled water, in comparison with similar products grown using alternative sources of water • Improving measurements of potential exposures to recycled water (eg through aerosols, consumption of irrigated crops and irrigation of household gardens) • Improving assessments of potential impacts of recycled water on soils and other receiving environments
• Assessing epidemiological effects of recycled water schemes • Community attitudes, behaviours and effectiveness of education programs on recycled water.
Element 10: Documentation and reporting Component Action Notes Management of documentation and records
• Document information pertinent to all aspects of recycled water quality management, and develop a document control system to ensure current versions are in use • Establish a records management system and ensure that employees are trained to fill out records • Periodically review documentation and revise as necessary
Reporting
• Establish procedures for effective internal and external reporting • Produce an annual report aimed at recycled water users, regulatory authorities and stakeholders
Documentation should: • Demonstrate that a systematic approach is established and is implemented effectively • Develop and protect the organisation’s knowledge base • Provide an accountability mechanism and tool • Facilitate reviews and audits by providing written evidence of the system • Establish due diligence and credibility.
Element 11: Evaluation and audit Component Action Notes Long-term evaluation of results
• Collect and evaluate long-term data to assess performance and identify problems • Document and report results
A systematic review of monitoring results over an extended period (typically the preceding 12 months or longer) is required to: • Assess overall performance against numerical guideline values, regulatory requirements or agreed levels of service • Identify emerging problems and trends • Assist in determining priorities for improving recycled water quality
• Establish processes for internal and external audits • Document and communicate audit results
External audits could be conducted on: • The management system • Operational activities • Recycled water quality performance • The effectiveness of incident and emergency response or other specific aspects of recycled water quality management • Environmental indicators and performance.
Element 12: Review and continual improvement Component Action Notes Review by senior managers
• Senior managers review the effectiveness of the management system and evaluate the need for change
In order to ensure continual improvement, the highest levels of the organisation(s) should review the effectiveness of the recycled water-quality management system and evaluate the need for change, by: • Reviewing reports from audits, recycled water quality performance, environmental performance and previous management reviews • Considering concerns of recycled water users, regulators and other stakeholders • Evaluating the suitability of the recycled water quality policy, objectives and preventive strategies in relation to changing internal and external conditions such as: – changes to legislation, expectations and requirements – changes in the activities of the organisation – advances in science and technology – outcomes of recycled water quality incidents and emergencies • Reporting and communication.
Recycled water quality management improvement plan
• Develop a recycled water quality management improvement plan • Ensure that the plan is communicated and implemented, and that improvements are monitored for effectiveness
Improvement plans may encompass: • Capital works • Training • Enhanced operational procedures • Consultation programs • Research and development • Incident protocols • Communication and reporting.
Appendix C – Treatment type descriptions Table 1: Group 1.0 – Aerobic treatment units Category Subcategory Description 1.1 Suspended growth The active biomass is suspended and mixed within
the bioreactor using forced aeration. Sludge (separated biomass) is returned to the secondary chamber to increase the mean sludge age.
1.1a Activated sludge (continuous aeration)
The bioreactor receives continuous aeration. Additional anoxic and anaerobic chambers are usually added to enhance nutrient removal.
1.1b Activated sludge (intermittent aeration)
Sludge (separated biomass) is returned to the primary chamber for anaerobic digestion. Aeration is intermittent to increase nutrient removal.
1.1c Membrane bioreactor
Suspended growth is used and membranes are employed to separate solids rather than a settling chamber, allowing for a higher loading rate and producing a high quality effluent.
1.2 Attached growth (forced aeration)
The active biomass is attached to support media or filters within a bioreactor. Forced aeration is used to provide oxygen using less energy than suspended growth.
Forced aeration is provided intermittently to enhance nutrient removal. Less energy is required for aeration than continuous aeration.
1.2c Fluidised bed The wastewater is forced up through a bed or granular media. Air or sometimes pure oxygen is added to the system.
1.2d Moving bed bioreactor
A unique submerged media with a high surface area is used to support the biomass. The media has a specific density to achieve vertical circulation within the bioreactor using forced aeration.
1.3 Attached growth (passive aeration)
Oxygen is provided to the attached biofilm by exposure to the atmosphere.
1.3a Percolating Filter (primary – septic tank)
The wastewater is percolated down through a bed of media. A septic tank or settling chamber is used to achieve primary treatment. Partial or full recirculation is usually required.
1.3b Percolating Filter (Primary – humus filter)
The wastewater is percolated down through a bed of media. A humus filter is used to achieve primary treatment, removing more solids and allowing for finer bed of media. Partial or no recirculation is usually required.
1.2d Rotating biological contactor
Large circular disks are partially submerged in the wastewater. They are rotated perpendicular to the flow in and out of the solution to aerate the attached biomass.
Appendix D – Evaluation criteria description Evaluation criteria Description
Organic impact
This includes the likely effluent quality in terms of BOD and SS.
Nutrient impact
This includes the likely effluent quality in terms nitrogen and phosphorus, which are the two nutrients of most concern.
Energy use
This refers to the amount of artificial energy input needed to complete the treatment process. It will in most situations refer to electricity requirement. The term ‘artificial energy’ is used to exclude any energy input from a direct natural source, such as gravity or heating from the sun.
Capital cost
Capital refers to the monetary cost of installing the complete treatment system and does not include additional costs associated with fluid conveyance pipe work.
Management cost
The cost of management and maintenance of the treatment system per year
Involvement
This includes the level of involvement and awareness that the individual home owner will be obligated to. A score of zero would associate with a deep sewerage home, where as a village scale treatment system would still require some awareness as to what is put down the drain. Composting systems generally have a high involvement.
Sludge The amount of waste sludge produced by the treatment system that will require further management (reuse/disposal)
Footprint The footprint is the total land area required by the treatment system. It does not include the area required for irrigation purposes.