Characterization of Water Treatment Plant's Sludge ...

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ScienceDirect Procedia Environmental Sciences 35 (2016) 950 – 955

International Conference on Solid Waste Management, 5IconSWM 2015

Characterization of Water Treatment Plant’s Sludge and its Safe Disposal Options T. Ahmad*, K. Ahmad, M. Alam* Department of Civil Engineering, Jamia Millia Islamia, New Delhi, India

Abstract Surface water Treatment for potable supplies typically involves coagulation, flocculation, Sedimentation, and filtration processes for removing colloidal as well as suspended solids from raw water. All water treatment plants (WTPs) produce waste/residue known as water treatment sludge (WTS) during the purification of raw water. The sludge produced a WTP at Ghaziabad, India is investigated for physical and chemical characteristics. It consist of about 60% fine sand in grain size range 150-75μ. Silica, alumina, ferric oxide and lime constitute the major percentage of chemical components present in the sludge. Some heavy metals are also found in the sludge. Discharging WTS into river, streams, ponds, lakes, drains etc. or landfilling the dewatered WTS is not environment friendly disposal option. Based on the characteristics, sustainable and profitable disposal through recycling and reuse have been reviewed. Utilization of WTS in brick making, in ceramics making, in the manufacture of cement and cementitious materials and as a substitute to building materials could provide safe disposal route. Reuse in wastewater treatment, in removal of heavy metals from aqueous solutions and in nutrient reduction from laden soils and runoffs are also some of the possible alternatives. It is required to explore suitable option for developing sustainable sludge management strategies under stringent environmental norms. © 2016 Published by Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license 2016The TheAuthors. Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility ofthe organizing committee of 5IconSWM 2015. Peer-review under responsibility of the organizing committee of 5IconSWM 2015 Keywords:Water Treatment, Sludge, Characterization, Disposal, Reuse options;

1.0 Introduction The Planning Commission, Government of India has estimated the water demand increase from 710 BCM (Billion Cubic Meters) in 2010 to almost 1180 BCM in 2050. Domestic and industrial water consumption is

* Corresponding author. E-mail address:[email protected]

1878-0296 © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of 5IconSWM 2015 doi:10.1016/j.proenv.2016.07.088

T. Ahmad et al. / Procedia Environmental Sciences 35 (2016) 950 – 955

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expected to increase almost 2.5 times (CPCB report 2011). The rapid growth of population and the trend of urbanization in India have exerted the potable water demand. Therefore, requires exploration of raw water sources and development of efficient treatment and distribution systems. The conventional Water treatment plant involves the process of coagulation, flocculation, sedimentation, filtration and disinfection. Large volumes of sludge or residues are generated during the processing of raw water to make it fit for drinking purpose. A typical water treatment plant produces about 100,000 ton/year of sludge (Bourgeois et al., 2004). India is also producing huge amount of inevitable waste everyday at their WTPs which requires proper handling and disposal. But, due to lack of sludge management strategies most of the WTPs in India discharge their filter backwash water and sludge into nearby drains which ultimately meet the water source. Some of the WTPs dispose the clarifier sludge on nearby open lands (CPCB report, 2011). Aluminium salts (e.g. Al2(SO4)3.18H2O) or Iron salts (e.g. FeCl3.6H2O, FeCl2, FeSO4.7H2O) are commonly used as coagulants (Sales et al., 2011). These salts get hydrolysed in water to form their respective hydroxide precipitates. Colloidal and suspended impurities such as sand, silt, clay, humic particles present in the crude water are removed by charge neutralisation, sweep floc mechanism and adsorption onto hydroxide precipitates (Trinh and Kang, 2011). The hydroxide precipitate along with sand, silt, clay and humic particles removed from the raw water mainly constitute the solids present in the sludge.The moisture content of the wet sludge is generally above 80 wt%. (Tantawy et al., 2015). In general, this sludge is discharged directly into nearby hydric bodies or dumped in the landfills after dewatering. The simple method of final disposal, although less expensive, is not a proper solution due to the possibility of contamination of water bodies and soil from the chemical products used in the treatment. However, with the realisation of adverse environmental impacts, it is likely that stringent regulations would be implemented soon. Therefore, development of sustainable sludge management strategies under stringent environmental norms is a challenging task for environmental scientists and engineers. This has initiated greater interest in exploring the reuse options for these discarded wastes/residuals. The main objective of the study is to investigate the properties of dewatered sludge produced in the WTP at Ghaziabad. This study also presents the review of related reuse options that have been identified globally to solve the problem of sludge disposal. 2.0 Materials and Method Dewatered sludge cakes have been collected from the WTP at Ghaziabad. This plant is treating Ganga river water coming from Haridwar through a canal and having a capacity of 120 MLD (Million Litres per Day). Polyaluminium chloride (PACl) is used as a coagulant to remove the colloidal and suspended impurities. Sludge produced during coagulation-flocculation process is passed through the dewatering facility and the dehydrated sludge is subjected to land filling. Therefore, representative samples of dehydrated sludge are brought to the laboratory for physical and chemical analysis. The collected samples have been tested for basic physical parameters such as pH and moisture contentaccording to Indian standard codes for testing soil samples. Volatile mater, ash content and loss on ignition are also determined by heating in a muffle furnace. Grain size distribution has been analysed through sieve analysis and hydrometer analysis. The major chemical compounds of the dry sludge have been analysed by energy dispersive X-ray fluorescence (ED-XRF) technique whereas trace elements are determined by wavelength dispersive X-ray fluorescence (WD-XRF) technique. 3.0 Results and Discussion 3.1 Physical characteristics Table 1 shows thepH, moisture content, volatile mater, loss on ignition and ash content of the sludge. Sludge sample was almost dry therefore moisture content is found to be only 2.35%. The volatile matter present in the sludge is low as 2.66% indicates that the sludge is inorganic in nature. Ash content of the sludge is found to be 89.78% whereas Loss on Ignition is 8.96%. Fig.1 shows the particle size distribution of the sludge. About 60% fine sand ranging between 150-75μm, 24% silt and 16% clay constitute the sludge.

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Table 1. Physical characteristics of the dry WTS pH

6.82

Moisturea (%)

2. 35

Volatile matterb (%)

2.66

Ash content (%)

89.78

Loss on Ignitionc (%)

8.96

80

20

4.75

2

0.3 0.425

0.15

a Heated at 105±5ƕC for 24 hours Combusted at 550±5ƕC for 2 hours c Fired at 1000±5ƕC for 2 hours

0.075

b

100 PERCENTAGE PASSING

90 80 70 60 50 40 30 20 10 0 0.0001

0.001

0.01

0.1

1

10

100

PARTICLE SIZE (mm) Fig.1 Particle size distribution of WTS

3.2 Chemical characteristics Major chemical composition of the sludge is shown in Table 2. SiO2 (52.78%), Al2O3 (14.38%) Fe2O3 (5.20%) and CaO (4.39%) are the main components of the sludge. This WTP produces Al based sludge as PACl is used as a coagulant. Some trace metals are also found in the sludge that is given in Table 3. Some metals are present in the alarming concentrations in the dried sludge. Barium, lead, arsenic and other heavy metals may cause significant damage to the environment if WTS is not disposed properly. Table 2. Chemical composition of WTS Components

%W/W

SiO2

52.78

Al2O3

14.38

Fe2O3

5.20

CaO

4.39

K2O

3.62

T. Ahmad et al. / Procedia Environmental Sciences 35 (2016) 950 – 955 Components

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%W/W

MgO

3.08

NaO2

0.97

TiO2

0.61

P2O5

0.17

MnO

0.08

ZnO

0.01

Table 3. Trace metals present in the dry WTS Elements

ppm

Elements

ppm

Ba

749.554

Pb

32.747

Zr

184.564

Ni

27.021

Rb

168.18

Cr

17.587

Ce

152.846

Ga

15.444

Sr

87.932

As

15.223

Cu

35.025

Nb

13.481

4.0 Sustainable disposal and reuse of water treatment sludge Simply discharging the WTS into drains or landfilling the dewatered WTS is not a sustainable disposal option. Hence, there is need to find some environmental friendly, sustainable and at the same time economical solution. The physio-chemical characteristic of the above sludge is similar to the WTS investigated in other countries of the world (Huang et al., 2013, 2005; Yen et al., 2011). These characteristics permit the constructive utilization of WTS in brick making (Chiang et al., 2009; Huang et al., 2005;Ramadan et al., 2008), in ceramic makingKizinievic et at., 2013; Teixeira et al., 2011) and in manufacture of cement (Pan et al., 2004; Rodríguez et al., 2011; Yen et al., 2011), cementitious materials (Alqam et al., 2011; El-Didamony et al., 2014;Rodríguez et al., 2010) , and light weight aggregate (Huang et al., 2013; Sales et al., 2011). Huang et al., 2005 reported that up to 15% WTS can be added to produce first degree brick at the temperature commonly attained in the brick kiln. Teixeira et al. (2011) incorporated the Brazilian WTP sludge into ceramic materials and found that sludge can partially substitute the clays used to produce ceramic bricks. Upto 10% incorporationand firing temperature lower than 1000°C produces solid bricks in compliance with Brazilian technical standards. However, above this temperature up to 20% addition into the raw material is feasible for the production of bricks and also roof tiles.Moreover heavy metals present in the sludge also get intact into the final product as sintering at higher temperature bond the materials together, forming sintered matrices (Wang et al., 1998).Hence, sintering of the WTS gives significant strength and extremely low heavy metal leachability. Chen et al. (2010) replaced shale with WTS from 4 to 10% in the cement production and found that 3day and 7day strength is higher than the control specimen in all cases. However, 28day strength increases significantly only up to 5.5% and starts decreasing rapidly after 7% replacement. Chen et al. (2010) and Pan et al., 2004 reported that all the heavy metals of the WTS got incorporated into the clinkers as leachate contained undetectable level confirming the environment friendly disposal option. Rodríguez et al., (2010) and Zamoraet al., (2008)substituted WTS as supplementary cementitious material and sand in preparation of cement mortar and concrete.

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Other feasible alternatives to solve the problem of sludge discharge includes coagulant recovery and reuse (Cherifi et al., 2011), as coagulant in wastewater treatment (Hong et al., 2005), as low cost adsorbent for phosphorus, hydrogen sulphide, boron, fluorides, perchlorate, glyphosate, mercury, arsenate, lead and selenium (Yang et al., 2014), as main substrate in constructed wetlands (Babatunde et al., 2011,Zhao et al., 2011)as soil buffers (Elliot and Dempsey, 1991; Fan et al., 2014) and in nutrient reduction from nutrients laden soils and runoffs (Novak and Watts, 2004). In India, coagulant recovery and reuse technology is under execution for viability of pilot scale. This technology shall be examined for cost optimization and to reduce the burden on safe disposal of sludge (CPCB report, 2011). Nair and Ahammed, (2014) investigated the Al based sludge produced in Katargam WTP at Surat, India as coagulant for post-treatment of UASB reactor treating urban wastewater. 74% removal of COD and 89% removal of turbidity from the UASB effluent could be achieved at the optimum conditions. 5.0 Conclusions Water treatment sludge produced at Ghaziabad WTP contains about 60% fine sand, 24% silt and 16% clay. Silica, alumina, lime and ferric oxide are 52.78%, 14.38%, 5.20%, 4.39% respectively. Lead, chromium, arsenic, barium and other metals are present in significant concentration. Therefore, Simple method of discharging sludge directly into nearby hydric bodies or dumping in the landfill sites is not sustainable solution. It is need to develop suitable sludge management strategies for sustainable development. Recycling the sludge in building and construction industry could be a safe disposal option. Construction industry has a growing market in India therefore; utilization of sludge/waste from WTPs would also prevent the excessive exploitation of raw materials and pave the way for sustainable development. Other options of sludge utilization in wastewater treatment, in removal of heavy metals from aqueous solutions and in nutrient reduction from laden soils and runoffs also possess great potential to reduce the burden on safe disposal. However, require exhaustive research to develop proper sludge management strategies for sustainable development under stringent environmental norms. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Alqam, M., Jamrah, A., Daghlas, H., 2011. Utilization of cement incorporated with water treatment sludge, Jordan J. Civ. Eng. 5 (2) 268– 277. Babatunde, A.O., Zhao, Y.Q., Doyle, R.J., Rackard, S.M., Kumar, J.L.G., Hu Y.S., 2011. Performance evaluation and prediction for a pilot two-stage on-site constructed wetland system employing dewatered alum sludge as main substrate. Bioresour. Technol. 102, 5645–5652. Bourgeois, J.C., Walsh, M.E., Gagnon, G.A., 2004. Treatment of drinking water residuals: comparing sedimentation and dissolved air flotation performance with optimal cation ratios. Water Res. 38, 1173–1182. Chen, H., Mab, X., Dai, H., 2010. Reuse of water purification sludge as raw material in cement production. Cem. Concr. Compos. 32, 436– 439. Cherifi, M., Hazourli, S., Pontvianne, S., Leclerc, J.P., Lapicque, F., 2011. Electrokinetic removal of aluminum from water potabilization treatment sludge, Desalina-tion 281 (17) 263–270. Chiang, K.-Y., Chou, P.-H., Hua, C.-R., Chien, K.-L., Cheeseman C., 2009. Lightweight bricks manufactured from WTS and rice husks. J. Hazard. Mater. 171, 76–82. CPCB (Central Pollution Control Board), report 2011. Status of WTPs in India. El-Didamony, H., Khalil, K.A., Heikal, M., 2014. Physico-chemical and surface characteristics of some granulated slag–fired drinking water sludge composite cement pastes. HBRC J. 10, 73–81. Elliott, H.A., Dempsey, B.A., 1991. Agronomic effects of land application of WTS. J. Am. Water. Works Assoc. 83(4), 126-131. Fan, J., He, Z., Ma, L.Q., Yang, Y., Stoffella, P.J., 2014. Impacts of calcium water treatment residue on the soil-water-plant system in citrus production. Plant Soil. 374,993–1004. Hong, G.X., Hao, C.G., Chii, S., 2005. Re-use of water treatment works sludge to enhance particulate pollutant removal from sewage, Water Res. 39 (15) 433–3440. Huang, C., Pan, J. R., Liu, Y., 2005. Mixing water treatment residual with excavation waste soil in brick and artificial aggregate making. J. Environ. Eng. 131, 272-277. Huang, C.-H., Wang, S.-Y., 2013. Application of WTS in the manufacturing of lightweight aggregate. Constr. Build. Mater. 43, 174–183. Kizinievic, O., Zurauskiene, R., Kizinievic, V., Zurauskas, R., 2013. Utilisation of sludge waste from water treatment for ceramic products. Constr. Build. Mater. 41, 464–473. Nair, A.T. Ahammed, M.M., 2013. The reuse of WTS as a coagulant for post-treatment of UASB reactor treating urban wastewater. Article in press, J. Clean. Prod., 1-10. Novak, J.M., Watts, D.W., 2004. Increasing the phosphorus sorption capacity of south eastern Coastal Plain soils using water treatment residuals. Soil Sci. 169, 206–214. Pan, J.R., Huang, C. Lin, S. 2004. Reuse of fresh water sludge in cement making. Water Sci. & Tech. 50(9), 183-188. Ramadan, M.O., Fouad, H.A., Hassanain, A.M., 2008. Reuse of water treatment plant sludge in brick manufacturing. J. Appl. Sci. Res. 4 (10), 1223–1229.

T. Ahmad et al. / Procedia Environmental Sciences 35 (2016) 950 – 955 19. Rodríguez, N. H., Ramírez, S. M., Varela, M.T.B., Guillem, M., Puig, J., Larrotcha, E., Flores, J., 2011. Evaluation of spray-dried sludge from drinking water treatment plants as a prime material for clinker manufacture. Cem. Concr. Compos. 33, 267–275. 20. Rodríguez, N. H., Ramírez, S. M., Varela, M.T.B., Guillem, M., Puig, J., Larrotcha, E., Flores, J., 2010. Re-use of drinking WTPs (DWTP) sludge: characterization and technological behaviour of cement mortars with atomized sludge additions. Cem. Concr. Res. 40, 778–786. 21. Sales, A., De Souza, F.R., Almeida, F.R., 2011. Mechanical properties of concrete produced with a composite of water treatment sludge and sawdust. Constr. Build. Mater. 25(6), 2793–2798 22. Tantawy, M.A., 2015. Characterization and pozzolanic properties of calcined alum sludge. Materials Research Bulletin 61, 415–421. 23. Teixeira, S.R., Santos, G.T.A., Souza, A.E., Alessio, P., Souza, S.A., Souza. N.R., 2011. The effect of incorporation of a Brazilian WTPs sludge on the properties of ceramic materials. Appl. Clay Sci. 53, 561–565. 24. Trinh, T.K., Kang, L.S., 2011. Response surface methodological approach to optimize the coagulation-flocculation process in drinking water treatment. Chem. Eng. Res. Des. 89, 1126-1135 25. Wang, K., Chiang, K., Perng, J., Sun, C., 1998. The characteristics study on sintering of municipal solid waste incinerator ashes. J. Hazard. Mater. 59, 201–210. 26. Yang, L., Wei, J., Zhang, Y., Wang, J., Wang D., 2014. Reuse of acid coagulant-recovered drinking waterworks sludge residual to remove phosphorus from wastewater, Appl. Surf. Sci. 305, 337–346. 27. Yen, C.-L., Tseng, D.-H., Lin, T.-T., 2011. Characterization of eco-cement paste produced from waste sludges. Chemosphere 84, 220–226. 28. Zamora, R.M.R., Alfaro, O.C., Cabirol, N., Ayala, F.E., Moreno, A. D., 2008. Valorization of drinking water treatment sludges as raw materials to produce concrete and mortar, Am. J. Environ. Sci. 4 (3) 223–228. 29. Zhao, Y.Q., Babatunde, A.O., Hu, Y.S., Kumar, J.L.G., Zhao, X.H., 2011. Pilot field-scale demonstration of a novel alum sludge-based constructed wetland system for enhanced wastewater treatment. Process Biochem. 46, 278–283.

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