Indrajit Deshmukh Ppr

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Reprint ISSN 0974-1518

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(IJERIA)

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International J. of Engg. Research & Indu. Appls. (IJERIA).ISSN 0974-1518, Vol.7, No. II (May 2014), pp. 73-84

PERFORMANCE OF HORIZONTAL ROUGHING FILTERFOR AUTOMOBILE INDUSTRY WASTEWATER

I. G. DESHMUKH., R. A. JOSHI AND V. B. PATILVishwakarma Institute of Information Technology,

Pune, Maharashtra, India.

Abstract

Rouhing filtration is an important pre-treatment process for wastewater, because it efficiently

separates fine solid particles over prolonged periods, without the addition of chemicals. For this study,

a laboratory scale plant was designed. The design and sizes of model are guided by Weglins Design

criteria. Gravel and plastic was used as filter media for the removal of turbidity and other parameters

etc.

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Keywords: wastewater treatment, horizontal roughing filtration http: //www.ascent-journals.com


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74 I. G. DESHMUKH., R. A. JOSHI AND V.B. PATIL

1. INTRODUCTION

Industrial pollution is one of the problem presently facing all the world and several efforts

are being vigorously pursued to control it. Wastewater systems are designed to treat water

become polluted by our day to day activities. If untreated wastewater is discharged into

natural water courses, it can cause public health and environmental problems.

Automobile industrial sector is one of the most important and largest industrial sectors of

India. It is one of the leading segments of the Indian economy. Automobile wastewater

contains substantial pollution loads in terms of Chemical Oxygen Demand (COD),

Biological Oxygen Demand (BOD), Total Suspended Solid (TSS), Total Dissolved Solid

(TDS) and heavy metals. It is typically alkaline, brown colored and has slightly high BOD

and high COD also high total solids (Wastewater treatment by Rao, Datta). conventional

physico-chemical, biological, chlorination and ozonation treatment processes used are

having certain problems associated with them. Also the treatment involves large amount of

acid, coagulants and energy. So there is need of effective and low cost technology for

treatment of wastewater.

Roughing filtration process efficiently separate fine solid particles over prolonged periods

without addition of chemicals. Roughing filters mainly acts as physical filters and reduce the

solid mass. However, the large filter surface area available for sedimentation and relatively

small filtration rates also supports adsorption as well as chemical and biological processes.

Therefore, besides solid matter separation, roughing filters also partly improve the

bacteriological water quality and, to a minor extent, change some other water quality

parameters such as colour, turbidity or amount of dissolved organic matter. Particle removal

efficiency in roughing filters is dependent on filter design, size of particulates, size of filter

media and water quality parameters. Horizontal roughing filters perform better than vertical

roughing filter ( Nkwonta, 2010).

The media used for horizontal roughing filter is gravel and plastic because it is locally

available and economical. The proposed work will focus on to find out the effective media

and filtration rate of horizontal flow roughing filter for automobile industry.

2. DYEING

Treatment of fiber or fabric with chemical pigments to impart color is called dyeing. The

color arises from chromophore and auxochrome groups in the dyes, which also cause


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PERFORMANCE OF HORIZONTAL ROUGHING 75

pollution (Pacini V., 2005). In the dyeing process, water is used to transfer dyes and in the

form of steam to heat the treatment bathsMore than 80,000 tonnes of reactive dyes are

produced and consumed each year. Once the dyeing operation is over, the various treatment

baths are drained, including the highly colored dye bath, which has high concentrations of

salt and organic substances. The wastewater must be treated before reuse.

Typical problems associated with wastewater encountered can be caused by high suspended

solids, turbidity, coliform bacteria, agricultural runoff. Previous studies have shown

roughing filtration to be an effective and reliable method for removing suspended solids,

turbidity and coliform bacteria (Nkwonta and Ochieng., 2004). For suspensions with

particulates that do not readily settle, roughing filtration provides superior treatment to basic

sedimentation methods (Wegelin, 1996) and represents an attractive alternative to more

costly conventional coagulation methods.

Roughing filters are primarily used to separate fine solids from the water that are only partly

or not retained at all by stilling basin or sedimentation tanks. Roughing filters mainly acts as

physical filters and reduce the solid mass. However, the large filter surface area available for

sedimentation and relatively small filtration rates also supports adsorption as well as

chemical and biological processes. Therefore besides solid matter separation, roughing filters

also partly improve the bacteriological water quality and, to a minor extent, change some

other water quality parameters such as colour or amount of dissolved organic matter

(Wegelin, 1996). Roughing filters are classified as deep-bed filters, whereby proper filter

design promotes particle removal throughout the depth of the filter bed, maximizing the

capacity of the filter to store removed solids. Particle removal efficiency in roughing filters

is dependent on filter design, particulate, and water quality parameters (Boller, 1993). Boller,

(1993) reported that reduction in turbidity from an average level of 23.05 NTUs to 22.82

NTUs using chemicals such as lime can cost $20 while roughing filters can reduce the same

quantity with $10. This shows that roughing filters are low cost treatment methods for water

and waste water.

3. ROUGHING FILTRATION PROCESS

Filtration is one of the oldest and simplest methods of removing contaminants in surface

water (Wegelin, 1996). Generally, filtration method includes slow sand filtration and

roughing filtration. The slow sand filters constructed in rural communities show that many of


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these filters have short filter runs and produce turbidity in the excess of the WHO guideline

values for drinking water. Reliable operation of sand filtration is possible when the raw

water has moderate turbidity and moderate suspended solids. For this reason, when surface

waters are highly turbid, ordinary sand filters could not be used effectively. Therefore, the

roughing filters are used as pretreatment systems prior to sand filtration (Oching G.M. et.al.,

2004). Furthermore, roughing filters could reduce organic matters from wastewater.

Therefore, roughing filters can be used to polish wastewater such as mine water before it is

discharged to the environment (Nkwonta, 2010). Although roughing filtration technology is

used as pretreatment to remove turbidity and followed by slow sand filtration, it may be used

without slow sand filtration if raw water originates from well protected catchment and if it is

free from bacteriological contamination (Wegelin, 1996). Roughing filters use natural

purification processes and no chemicals are necessary. Besides these, filters could be built

from local materials and manpower. These filters will work a long time without maintenance

(Wegelin, 1986). Therefore, roughing filters are appropriate and economical.

4. HORIZONTAL FLOW ROUGHING FILTERS

As shown in Figure 2.2., unlimited filter length and simple layout are the main advantages of

horizontal roughing filters (Wegelin, 1996). Horizontal roughing filters have a large silt

storage capacity. Solids settle on top of the filter medium surface and grow to small heaps of

loose aggregates with progressive filtration time. Part of the small heaps will drift towards

the filter bottom as soon as they become unstable. This drift regenerates filter efficiency at

the top, and slowly silts the filter from bottom to top (Wegelin, 1996).

Fig .No.2.2. Shows the diagram of horizontal roughing filter (Nkwonta.,2010)


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Horizontal-flow roughing filters also react less sensitively to filtration rate changes, as

clusters of suspended solids will drift towards the filter bottom or be retained by the

subsequent filter layers. Horizontal-flow roughing filters are thus less susceptible than

vertical-flow filters to solid breakthroughs caused by flow rate changes. However, they may

react more sensitively to short circuits induced by a variable raw water temperature

(Wegelin, 1996).

5. ROUGHING FILTER DESIGN PARAMETERS

The basic roughing filter design parameters may classified to include the following

1. Filter media sizes

2. Filtration rate

3. Filter length.

5.1 Filter media size

Media types commonly used in roughing filtration are quartz sands and gravels but can be

replaced by any clean, insoluble, and mechanically resistant material (Ochieng and Otieno,

1988). Previous work by Wegelin showed that the effect of surface porosity and roughness

of filter media on particle removal efficiency in roughing filtration was insignificant

compared to the size and shape of macro-pores in the filter. The removal efficiencies in

calcite limestone, basaltic river rock, and limestone-amended basalt horizontal roughing

filters and found only marginally improved efficiency (7%) for calcite amended basalt filters

over unaltered filters. Improved removal efficiencies are generally correlated to smaller

media sizes (Wegelin, 1986).

The use of multiple grades of filter media in a roughing filter promotes the penetration of

particles throughout the filter bed and takes advantage of the large storage capacities offered

by larger media and high removal efficiencies offered by small media. The size of filter

media decreases successively in the direction of water flow, and ideally the uniformity of

filter media fractions is maximized to increase filter pore space (storage capacity) and aid in

filter cleaning (Boller, 1993). Common grades of media used in horizontal roughing filtersare provided by Wegelin (1996) and shown in Table 2.1.


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Table 2.1. Description of HRF for Gravel Media

Table 2.2. Description of HRF for Plastic Media

Table 2.3. Description of HRF for Mixed MediaFor mixed media

Effective

size Filtration Rate

Length of

Compartment

No. of

days

5 mm 0.5 m/h 1 m/h 1.5 m/h 0.2 m 90

10mm 0.5 m/h 1 m/h 1.5 m/h 0.2 m 90

Plastic

media

0.5 m/h 1 m/h 1.5 m/h 0.2 m 90


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5.2 Mechanism of roughing filters

Fig. No. 2.7. Mechanism of roughing filters (Nkwonta., 2010)

As illustrated in Figure, water has to undergo a step to step treatment especially if it contains

differently sized impurities. The first and easiest step in sound water treatment schemes is

coarse solids separation. Finer particles are separated in a second pretreatment step and,

finally, water treatment will end with the removal or destruction of small solids and

microorganisms. These different pretreatment steps will contribute to reducing the pathogenic microorganisms. The pathogens attached to the surface of suspended solids will

get stranded when the solids are separated. Some of the microorganisms floating in the water

might also get pushed to the surface of the treatment installations and adhere to biological

films. Solid matter and microorganisms, therefore, face a multitude of treatment barriers .

Since treatment efficiency of each barrier increases in the direction of flow, it becomes

increasingly difficult for the impurities to pass through each subsequent treatment barrier.

Removal of suspended solids in roughing filters requires laminar flow. Hydrodynamic forces

that move the water through the pore system create patterns of flow retardation andacceleration that have pockets of stagnant water near the media surface allowing particles to

settle and it is shown in Figure 2.8. A sticky organic film on the surface of the media in the

pores retains the suspended solids by mass-particle attractions through the Vander Waals

forces and electrostatic forces between charged particles (Wegelin,1996).


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Fig. No.2.8. Solids removal in HRF (Wegelin, 1996)

5.3 Advantages of roughing filters over conventional methods.

Conventional system is quite demanding in chemical use, energy input and mechanical parts

as well as skilled manpower that are often unavailable, especially in rural areas of

developing countries. But roughing filters do not require chemical use, and mechanical parts.

Conventional methods demand high operating costs than roughing filters.

5.4 Disadvantages of roughing filters over conventional methods.

Colour removal is fair to poor and in some cases it requires a large area of land for effective

treatment. It can handle only relatively moderate strength wastes compared to conventional

methods. It also can handle only very moderate organic loads compared to conventional

treatment methods such as activated sludge process.


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6. EXPERIMENTAL SETUP OF LAB-SCALE MODEL OF HORIZONTAL

ROUGHING FILTERS

The experimental laboratory scale model of the HRF was fabricated with an acrylic plastic

transparent sheet of 6 mm thickness. The set up is based on the HRF systems and is shown in

fig 2.5. The Components of the set up are overhead feed tank, three inlets with flow

regulator, HRF system and outlet arrangement for effluent. The HRF is fed by overhead feed

tank, which is placed on steel base. The tank is made up of plastic and has 100 L capacity. It

is kept at an elevated level so that sufficient head is created for flow by gravity. The inlet

arrangements to HRF system consist of a valve, which are used for regulating flow to filter

and is made up of plastic of size inch. The main component of the experimental set up is

HRF system which is made up transparent glass sheet. The experimental setup with auxiliary

units and working model is shown in figure (2.9). The dimensions of each HRF unit were 60

cm long, 20 cm width and 20 cm depth.

To enable a comparative study, three horizontal roughing filters that consist of three

compartments each were constructed. The design and sizing of the pilot plant was guided by

the wegelin design criteria (Wegelin, 1986). This study aimed at verifying these criteria

based on gravel as a filter medium and other available possible filter media, namely plastic.

Each filter was filled with a different filter medium and was separated with an iron mash in

the direction of flow. The filter bed was provided with under drain system, so that it would

allow for cleaning of the filters after a certain period. So a constant filtration rate of 0.5, 1

and 1.5 m/h was used. Percentage removal of the units for the textile wastewater quality

parameters was obtained as a measure of performance. Sampling was done three times a

week for a period of 90 days. The sampling points were the inlets and outlets of the

horizontal roughing filter units.

6.1 Commissioning of the laboratory scale model.

The filter ran for 90 days from the day of commissioning. The filter was used to conduct test

work on the efficiency and effectiveness of the easily available media such as plastic andgravel in removing parameters such as TDS, TSS, COD, BOD and pH values of the textile

wastewater was also monitored


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Table 2.3: Methods used for analysis.

Sr. no Parameters Methods used for analysis

1 pH Electrometric method.

2 BOD Titration by iodometric method.

3 COD COD analyzer with reflux method

4 TDS TDS meter.

5 TSS Filtration method

The flow was regulated by trial and error to set the desire flowrate. All the parameters were

analyzed as per Standards methods for examination of water and wastewater prescribed by

American Public Health Association (APHA, 1995).The parameters and methods used for

determination are represented in Table 2.3.

6.2 Experimental Procedure.

The experimental set up was initially run for acclimization process to develop biomass on

media surface area. The HRF was operated for a initial flow rate of 0.5 m/h for around 30

days continuously.

After development of bacteria the HRF was operated for varying flow rates of 0.5, 1, 1.5 m/h

for 30 days each. Each flow rate was operated till the constant removal efficiency was

achieved. If removal efficiency goes on decreasing then cleaning of filter was done. The

analysis is done three times in a week.

The filter media and filtration rate is very much important and which affects removal

mechanism and efficiency. Comparison between gravel and plastic media in treatment of

wastewater for varying flow rates is to be done. Effective filter media and flow rate for

treatment of textile wastewater is to be determined.

Table 3.1 : Characterization of raw effluent from Tata Automobile Industry Pune.

Sr. No Parameter Raw Effluent

1 pH 6.7-7.5

2 COD mg/L. 1300 300

3 BOD mg/L. 292 20


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4 Total Suspended Solid (TSS) mg/L 900 100

5 Total Dissolved Solid (TDS ) mg/L 575 25

6 Alkalinity mg/L as CaCo3 17 0.5

6.3 Application of HRF for Treatment of Textile Effluent.

The HRF was used to treat effluent from textile effluent treatment plant. The HRF was

operated at varying flow rates such as 0.5, 1 and 1.5 m/h. The performance evaluation of this

system is discussed for various parameters in following section.

CONCLUSION

The present study was aimed to evaluate the potential of HRF in improving the effluent

quality from Textile Industry. HRF was assessed for different media and varying flow rates.

The performance evaluation was carried out for parameter viz pH, BOD, COD, TSS and

TDS. The flow rate was varied from 0.5 m/h to 1.5 m/h. All studies were carried out in

continuous mode of operation, based on the study carried out and result obtained following

conclusions are drawn,

1. The characterization study carried out for raw effluent shows that Textile Industrial

effluent which is amenable for treatment by HRF.

2. The optimum flow rate is found to be 1 m/h and maximum removal efficiency is found

to be for plastic media filter.

3. The removal efficiency of TSS at a flow rate of 1m/h for plastic, gravel and mixed

media are 92 %, 82% and 89% respectively.

4. The removal efficiency of TDS at a flow rate of 1m/h for plastic, gravel and mixed

media are 75 %, 48 % and 35 % respectively.

5. The removal efficiency of COD at a flow rate of 1m/h for plastic, gravel and mixed

media are 58 %, 46 % and 41 % respectively.

6. It was shown that plastic media performs better than gravel media in general removal

efficiency with regards to the parameters that were put to test. This observation could

have resulted from the reason that plastic media has a slightly higher specific surface

area and porosity respectively to enhance the sedimentation and other filtration

processes compared to gravel.


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Indrajit Deshmukh Ppr

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