Treatment of Sand Filter Backwash Water from Water Treatment Plant

International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 12130 - 12137

Ashutosh Diwakar1, Ahire Rituja2, Gosavi Shubhangi3, Ahire Suvarna4, Yakub Ansari5 1,2,3,4UG Scholar in Department of Civil Engg. MMANTC, Mansoora, Malegaon(Nashik), India 5Assistant Professor in Department of Civil Engg. MMANTC, Mansoora, Malegaon(Nashik), India

Abstract In this study several tests were conducted to investigate the possibility of re-use the filter backwash water. Backwashing is done to prevent sand-granular-gravel filter media from clogging due to increased passage of particles and microorganism. Which results in wastage of water, it is a very common problem in WTP. The amount of wash water generated estimated at a rate of (10-15%) of the amount of purified water in the plant. Sand filter backwash water (SFBW) and sludge water are generated in most of drinking WTP. Good quality of water can be obtained by recycling of SFBW by adopting proper treatment. Experiments were conducted on Raw Water (RW) and SFBW samples from Surface WTP. Reuse of SFBW is of great interest. Jar test was performed with other parameters such as turbidity, color, odor and total suspended solids were recorded for RW, SFBW and found significant differences. Results indicated that in quality of RW and SFBW can be achieved with proper treatment. Keywords: SFBW, RW, Filtration, Reuse, Pre-Treatment, Water, Activated Charcoal

1. Introduction Actually, only 1% of the world's water is usable to us. About 97% is salty sea water, and 2% is frozen in glaciers and polar ice caps. Thus that 1% of the world's water supply is a precious commodity necessary for our survival. Most drinking water systems use filters to collect, catches, or gather particles from an incoming flow. When the filter’s pores become clogged, they need to be cleaned. One of the best ways to clean a drinking water system’s filter is to backwash it, meaning reversing the flow and increasing the velocity at which water passes back through the filter. This, in effect, blasts the clogged particles off of the filter. Although every filter is unique, the principles of backwashing are similar for all of them. In current practice, conventional treatment processes including oxidation, coagulation, flocculation, sedimentation, and sand filtration are being used for treatment of ground or surface water. It is essential to perform regular backwashing of the sand filter (one/twice a day), to maintain the efficient flux in filtration. An average conventional water treatment plant (WTP) uses approximately 2–10% for drinking water produced in the plant itself. A backwash operation typically entails flushing the water in the reverse direction to that of normal flow. During the process, the accumulated contaminants are detached from the filter, and the resulting water is called sand filter backwash water (SFBW) that contains a high amount of suspended solid, colloidal materials, inorganic metals (Fe, Mn, and Al), natural organic matter, bacteria, viruses, invertebrates, and protozoa. Inorganic metals such as Fe & Mn and Separation of solids is essential to be removed for recycling of SFBW. One of the key methods for pre-treatment of SBFW is the coagulation and flocculation process. At first Pre-treatment is to be performed before the conventional water treatment methods. In this report the application of an alum coagulant in a coagulation/microfiltration process has been investigated. A previous study suggested that pre-coagulation of SFBW enhances the quantity and quality of filtrate water through, enlarging submicron particles that eventually delay the clogging of filter pores. Therefore, one of

International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 12130 - 12137 the most suitable options for recycling of SFBW from conventional water filters is pre-coagulation. As backwash water does not contain any significant amount of harmful impurities it does not affect the natural flow of river if drained directly into river. But when this backwash water is allowed to flow with domestic sewer lines it gets polluted and ultimately it pollutes the river in which it is drained. Nearly in ever water treatment plant across the country about 10% to 15% of plant capacity pure water is being used for filter backwash daily. This amount of water is being completely wasted daily. it is observed that SFBW contains about 2% to 5% impurities the rest is water. This water can be treated and reused for several purposes. By achieving this large amount of water can be saved across the country. After pre-treatment of SFBW impurities can be reduced significantly. Though, it can be said as Raw Water. This RW generated is then purified with conventional water treatment method. Activated charcoal is used for post treatment of SFBW. The use of special manufacturing techniques results in highly porous charcoals that have surface areas of 300-2,000 square meters per gram. These so-called active, or activated, charcoals are widely used to adsorb odorous or colored substances from gases or liquids. The aim of the current study is to investigate the feasibility of using filtration coupled with the activated charcoal and coagulation and flocculation process to treat the SFBW and to produce high-quality potable water.

2. Lıtrature Revıew Mangesh L. Jibhakate.et al.1 Author have concluded that for filtration Sand filters are generally used in WTP. Due to continuous filtration process, sand pores get clogged and decreases the efficiency. To overcome this problem, backwashing is carried out by flow of water & air through filter media. The present study includes a trial for the recirculation and reuse of backwash water. Sarra Ikhlef. et al.2 They have done ressearch on Backwash Optimization for Drinking Water Treatment Biological Filters, Engineering, Carleton University, Ottawa-Carleton Institute of Civil and Environmental Engineering. January 2016. They have concluded that the backwash procedures showed no consistent impact on bio filters' biomass concentrations as measured by the phospholipids and the adenosine tri-phosphate (ATP) methods. Sagar Suman et al.3 Done research work on Effect of Filter Backwash Water when blends with Raw Water on Total, Organic Carbon and Dissolve Organic Carbon Removal, The concluded that In most of the drinking WTP filter backwash water (FBWW) and clarified sludge water (CSW) are generated. Reuse of FBWW is of great interest. Recycling of FBWW and its suitable treatment is possible in order to provide guarantee of water quality. S. Vigneswaran et al.4 Have worked on filtration technologies in wastewater treatment. This chapter commences with a discussion on the use of deep bed filtration in wastewater treatment and introduces other related filtration technologies such as cartridge filtration, microstrainer, precoat filtration. Kameran Mohammed Ali. et al.5 They have worked on Role of different, Filter media in water, Purification and water Treatment, In this research they have introduced and focused on water purification through the types of water treatment Plants. Emphasis was placed on the type of materials (media) used in the Filters, Together with the standard specifications, tables and curves of head losses during Filtrations and backwashing for each media type. Then displayed models of the designs of filters in water treatment

International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 12130 - 12137

Plants in some Kurdistan cities. Florian G. Reissmann. et al.6 Authors have done research on Ultrafiltration (UF) for the reuse of spent filter backwash water (SFBW) from drinking water treatment. They have focused on improving the backwash water quality to reuse; major water quality indicators were always below corresponding drinking water limits as well as raw water concentrations. As a result, the reuse of UF treated SFBW should not lead to an influence of drinking water quality.

3. Iıı Scope Of Research According to the Central Water Commission, India needs a maximum of 3,000 billion cubic meters of water a year. It is been estimated that 85 to 120 billion cubic meters of water is being used for filter backwashing across the country in a year. All treatment methods have some disadvantages, but as we have previously seen in this report needs of water are increasing. And large quantity of water is wasted daily which is used for filter backwashing. Treating of Filter backwash water can save up to 75 to 110 billion cubic meters of water can be reused in a year. A. Study of Gravity Type Rapid Sand Filters Filtration is the process of passing water through material to remove particulate and other impurities, including flock, from the water being treated. These impurities consist of suspended particles (fine silts and clays), biological matter (bacteria, plankton, spores, cysts or other matter) and flock. The material used in filters for public water supply is normally a bed of sand, coal, or other granular substance. B. Testing of SFBW RW and SFBW samples where tested for physical and chemical characteristics in which Turbidity, Sludge Value Index, Color, Odor, Temperature, Taste and pH respectively. These tests showed up with the result that approximately 95% to 98% of water can be used after conventional water treatment method followed by activated charcoal filtration. C. Analyze the quality of water Physical properties of water have been tested including temperature and turbidity. pH of SFBW is observed under Chemical characteristics. It is observed that SFBW contains about 2% to 5% of impurities in it and these should be removed for safe use of water. Jar test was performed for determination of alum dosage for SFBW, four different samples were collected while backwashing for testing. This showed up following results;

International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 12130 - 12137

Figure 1 Turbidity and pH Test results

4. Treatment of SFBW SFBW can be efficiently and economically treated by installation of a pilot sized treatment unit at the existing water treatment plant. It will require a lesser area in the plant and also its installation will be easy as compared to a whole treatment plant. SFBW is treated by adopting following process; Plain sedimentation is adopted as pre-treatment of SFBW. Sludge Volume Test was conducted on SFBW. The observation is made that SFBW contains large quantity of settable solids. Table 1 SVI Test Results Sr. No. Sample Sludge Volume Index 30 min 60 min 1 SFBW before passing compressed air 8.5 8.9 2 SFBW while passing compressed air 16.9 14 3 SF flushed with pure water 11 9 4 SFBW at filter outlet 8 9

A. Coagulation and Flocculation Coagulation and flocculation are important processes in water treatment with coagulation to destabilize particles through chemical reaction between coagulant and colloids, and flocculation to transport the destabilized particles that will cause collisions with floc. It is used to remove particulate impurities, especially non settleable solids (particularly colloids) and color from the water being treated.

B. Filtration Filtration is the process of passing water through material to remove particulate and other impurities, including flock, from the water being treated. These impurities consist of suspended particles (fine silts and clays), biological matter (bacteria, plankton, spores, cysts or other matter) and flock. The material used in filters for public water supply is normally a bed of sand, coal, or other granular substance.

International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 12130 - 12137

A conventional water filter is to be installed for filtration of SFBW. The filter media consists of sand layer (or sand bed) 60 to 75 cm thick. The effective size of the sand varies from 0.45 to 0.70 mm. It consists of coarse sand layers of effective size varying from 0.35 mm to 0.55 mm, having uniformity coefficient D60/D10 ranging from 1.2 to 1.8. The base material consists of gravel in thickness of 60-90 cm. usually five to six layers of 10-15 cots each are used. This filter is also needed to be backwashed after several hours of working for its maintenance. It requires 2% to 10% pure water of capacity of pilot sized WTP. This backwash water is then recirculated in sedimentation tank for pre-treatment of SFBW. It creates a continuous loop cycle of filtration of backwash water from sand filters. This filtered water is then further transported to an activated charcoal filter for post-filtration. Table 2 Jar Test Results on SFBW Sr. No. Sample Alum dose applied mg/l Initial Final Turbidity Lime Alum turbidity turbidity removed 1 SFBW before passing 0.5 1 61 6 60 compressed air 2 SFBW while passing 0.5 1 65 4 61 compressed air 3 SF flushed with pure water 0.5 1.5 61 5 56 4 SFBW at filter outlet 0.5 2 62 4 58

C. Activated Charcoal Filter The separate activated charcoal filtration unit is provided after filtration tank for post-treatment of Filtered water. Carbon filtering is a method of filtering that uses a bed of activated carbon to remove contaminants and impurities, using chemical absorption. One pound of activated carbon contains a surface area of approximately 100 acres. Activated charcoals are good at trapping other carbon-based impurities. It is widely used to adsorb odorous or colored substances from gases or liquids. Charcoal has the properties of absorbance of biological & chemical impurities. The huge surface area of activated charcoal gives it countless bonding sites. When certain chemicals pass next to the carbon surface, they attach to the surface and are trapped. It also means that, once all of the bonding sites are filled, an activated charcoal filter stops working. At that point you must replace the filter. It is a closed unit in which the layer of activated charcoal is sandwiched along with pervious membrane. The filtered water is passed from this unit. It adsorbs any odorous or colored substances, fine impurities which have been escaped from filtration unit.

D. Disinfection Post-treated water is disinfected by chlorination. Post-treated water may contain pathogenic bacteria and harmful microorganisms which are removed by chlorination. Water chlorination is the process of adding chlorine or chlorine compounds such as sodium hypochlorite to water. This method is used to kill certain bacteria and other microbes in water as chlorine is highly toxic.

International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 12130 - 12137

5. Results And Dıscussıon Figure 1 show the Turbidity and pH level of SFBW, from which observation were made that SFBW can be treated and made potable. SFBW is highly turbid and mainly contains silt, clay, organic and inorganic matter. pH of SFBW lies in between 5.5 to 7.5. As the observation were made that SFBW has high solid contain, that can be removed with plain sedimentation. SVI test was performed on four samples of SFBW. Table no 1 shows the result from SVI test on SFBW for suitable interval of time. These results showed that most of settable solids can be removed by plain sedimentation. Hence, plain sedimentation was adopted for pre-treating of SFBW. Table no 2 shows result from Jar Test, four different samples were tested. Different alum dosages were added in each sample, the table shows most suitable alum dosage for individual sample. After Coagulation with sedimentation impurities were reduced significantly. The final turbidity achieved was close to standard limit for drinking water as per IS 10500 (2012). Table 3 Turbidity after Treatment Sr. No. SFBW after filtration Initial turbidity Final turbidity Turbidity removed 1 A 6 1 5 2 B 4 0 4 3 C 5 0 5

Final turbidity test was conducted on SFBW after pre-treatment and post-treatment followed by activated charcoal filter. Results from this test are enclosed in Table no 3. The final results were satisfactory as the turbidity was reduced near to zero. CONCLUSION  Up to 95% of SFBW can be effectively treated to be used for drinking or any other purpose. By this problem of water scarcity can be solved up to certain limits.  As per Central Water Commission treating of SFBW can save up to 75 to 110 billion cubic meter of water can be reused across the country. Re-treated SFBW can serve water demand of approximately 1.2 to 2 million people per year.  After number of tests performed on SFBW final results were satisfactory.  As a separate unit is to be installed, treating of SFBW does not affect working of existing WTP. A vertical treatment unit can be introduced as it will require lesser area, making it economical and easy to operate.  Activated Charcoal Filter played an important role in removal of harmful impurities from water and enhances drinking water quality. Backwash water from the SFBW treatment unit is carried to the very first unit for plain sedimentation. From which it gets mixed with SFBW from the plant and re-circulated in treatment unit. This creates a continuous loop cycle of treatment of SFBW. We conclude that re-treating of SFBW can be one of the methods to face water scarcity issues across the globe. This treated water can be used for several purposes.

International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 12130 - 12137

References: 1. Indian Standard Drinking Water -Specification (Second Revision). IS 10500:2012. Ics 13.060.20, Bureau of Indian Standards Manak Bhavan, 9 Bahadur Shah Zafar Marg New Delhi 110002. 2. Sagar Suman, Singh N.P., Chandra Sulekh. 3. Effect of Filter Backwash Water when blends with Raw Water on Total Organic Carbon and Dissolve Organic Carbon Removal 4. Research Journal of Chemical Science, Vol. 2(10), 38-42, October (2012) Received 28th May 2012, Revised 2nd June 2012, accepted 7th June 2012, Available online at: www.icsa.in 5. Md Shafiquzzaman ID, Abdullah Al-Mahmud, Saleem S. Alsaleem ID and Husnain Haider Application of a Low-Cost Ceramic Filter For Recycling Sand Filter Backwash Water Received: 17 December 2017; Accepted: 30 January 2018; Published: 3 February 2018 6. S. Vigneshwaran, J. Kandasamy and M. Rogerson Filtration technologies in wastewater treatment. 7. Dana M. Johnson, Kevin D. Czupinski, MSBA, qigong zhang, jinxian tang, Feasibility of water purification technology in rural areas of Developing countries Journal of environmental management Submitted:may 19 ,2006 Revised and resubmitted :December 4,2006/February 2,2007 Guidelines-disposal methods for water filter backwash solids Water quality/waste water permits 02 may 2007 8. Dr Graeme K pearce, Hydranautics UK, Ms. Julie Allam and Javier suarez,Kalsep, And David James, purac Recovery of filter backwash Effluent using HYDRA cap UF at Seedy Mill ,South Staff water. 9. Dana M. Johnson, Kevin D. Czupinski, MSBA, qigong zhang, jinxian tang, Feasibility of water purification technology in rural areas of Developing countries Journal of environmental management Submitted:may 19 ,2006 Revised and resubmitted :December 4,2006/February 2,2007 Guidelines-disposal methods for water filter backwash solids Water quality/waste water permits 02 may 2007 10. Dr Graeme K pearce, Hydranautics UK, Ms. Julie Allam and Javier suarez,Kalsep, And David James, purac Recovery of filter backwash Effluent using HYDRA cap UF at Seedy Mill ,South Staff water 11. Mangesh L. Jibhalokhate, M. P. Bhorkar, A. G. Bhole, P. K. Baitule Reuse & Recirculation of filter backwash water of water Treatment water 12. Mangesh L. Jibhalokhate.et al. Int Journal of Engineering Research and Applications www.ijera.com ISSN: 2248-9622, vol.7, issue 4, (part-1) April 2017, pp.60-63 13. Hanan a. Fouad, rehab M. EI-hefny, Mahetab Ali Mohammed of spent filter backwash water, international of civil engineering and technology (IJCIET) Volume 7, issue 4, July –august 2016,pp. 176-187 article ID:IJCIET_ 07_04_014 Available onlineat; http://www.laeme.com/IJCIET/issue.ASP?Jtype=ijiciet&vtype=7&itype =4 AUTHORS PROFILE Ashutosh Diwakar, Department of Civil Engineering, MMANTC College of Engineering, University of Pune, Maharashtra, India.

Ahire Rituja, Department of Civil Engineering, MMANTC College of Engineering, University of Pune, Maharashtra, India. Have published 1 paper in National conference

Gosavi Shubhangi, Department of Civil Engineering, MMANTC College of Engineering, University of Pune, Maharashtra, India.

International Journal of Advanced Science and Technology Vol. 29, No. 7, (2020), pp. 12130 - 12137

Ahire Suvarna, Department of Civil Engineering, MMANTC College of Engineering, University of Pune, Maharashtra, India.

Yakub Ansari working as Assistant Professor in Civil Engineering Department in MMANTC Mansoora Nashik India. Have completed Master in Environmental Engineering, Working in academic from last 6 years and got Best Faculty Award for the year 2019. Have worked in many national and international company and worked in Qatar and Saudi Arab for 5 years. Have published 15paper out of which 3 paper published in International conference, have attended 3 International conference, Attained 5 FDP and 2 STTP program.