Psychology

Treatment of Landfill Leachate through Coagulation Process

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Landfill leachate can be defined as a liquid that passes through the municipal solid waste (MSW) landfill and has extracted dissolved and suspended matter from it. The generation of leachate is a major problem for MSW landfills and causes significant
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   M. Alamgir, K.A.B.M. Mohiuddin, S.M.T. Islam, and M.H. Hasan (Eds.)    ISBN: 978-984-33-8695-3, PI.95 (1-9)  Proceedings of the Waste Safe 2015  –  4 th  International Conference on Solid Waste Management in the Developing Countries 15-17 February 2015, Khulna, Bangladesh   Treatment of Landfill Leachate through Coagulation Process   Mohidul Islam, Islam M. Rafizul and Muhammed Alamgir Department of Civil Engineering, Khulna University of Engineering & Technology (KUET), Khulna-9203, Bangladesh (E-mail: moinulce09@gmail.com and  imrafizul@yahoo.com)  Abstract Landfill leachate can be defined as a liquid that passes through the municipal solid waste (MSW) landfill and has extracted dissolved and suspended matter from it. The generation of leachate is a major problem for MSW landfills and causes significant threat to surface water and groundwater. Special care is required for efficient treatment and disposal. In addition, landfill leachate is complex waste water with considerable variation in both quality and quantity. The composition and concentration of pollutants are influenced by the types of waste deposited, hydro geological factors and more significant by the age of the landfill site. In general, leachate is highly contaminated with organic contaminants measured as chemical oxygen demand (COD), biochemical oxygen demand (BOD) and also with high ammonium nitrogen concentration. The main focused of this research is to investigate the performance of chemical treatment by coagulation process and to compare the efficiency of coagulants on removal of COD and TSS with standard tools in leachate samples which was collected from Rajbondh landfill in Khulna. The collected leachate samples were tested in the laboratory through the standard methods to measure the relevant parameters. The characteristics of leachate were: pH=8.6; BOD5=142.1 mg/L; COD=5760 mg/L; Temperature=28.7ºC; Electric Conductivity=5.67µs/cm; TS=17000 mg/L; TDS=16600 mg/L; TSS=400 mg/L; Turbidity=336 NTU; Color=17800 pt-co; Alkalinity=1700 mg/L; Salinity=2800 mg/L; T.C.=740; F.C.=300. The coagulation of leachate was accomplished by a technique consisted of Poly-Aluminum Chloride (PAC), Aluminum Sulphate (Al  2  (SO 4  ) 3 .18H  2  O) as  Alum and Ferrous Sulphate (FeSO 4  ) in various dosages and different pH values (2, 5, 7 and 9). Results showed that the efficiency for COD removal by PAC at pH=9 and 2500 mg/L of coagulant dose, by Alum at pH=9 and 2500 mg/L of coagulant dose, by Ferrous Sulphate at pH=7 and 2000 mg/L of coagulant dose. The COD removal efficiency for PAC, Alum and Ferrous Sulphate were 81.82, 75 and 85.71% respectively. Results also showed that efficiency for TSS removal by PAC that was obtained at pH=5 and 2500 mg/L concentration of coagulant dose, by alum at pH=7 and 2500 mg/L concentration of coagulant dose and by ferrous sulphate at pH=9 and 2000 mg/L of coagulant dose. The TSS removal efficiency for PAC, Alum and ferrous sulphate are 46.15, 60 and 72.73% respectively. In this study carried out the COD and TSS removal efficiency both were better for ferrous sulphate. To depict the performance of used chemical coagulations then compared to the standards leachate discharge which are available in the literature.  Introduction Landfill leachate is defined as any contaminated liquid effluent percolating through deposited waste and emitted within a landfill or dump site through external sources, of which its route of exposure and toxicity often remains unknown. Throughout recent decades, the wastewater treatment industry has identified the emission of organic, inorganic and heavy metals compounds due to leachate seepage into the waterways as a risk the natural environments (Ghafari et al., 2010). Increasing the quality of life and industrial and commercial growth in many countries around the world in the past decades have been accompanied by rapid increases in both municipal and industrial solid waste production. MSW generation continues to grow both in per capita and overall terms (Melike et. al., 2007; Ajit Singh and Vidyarthi, 2008). The physical appearance of leachate when it emerges from a typical landfill site is a strongly-odoured, yellow or blackish coloured cloudy liquid and the smell is acidic and offensive. In some older landfills, leachate is directed to the sewers, but this can cause a number of problems. Toxic metals from   M. Alamgir, K.A.B.M. Mohiuddin, S.M.T. Islam, and M.H. Hasan (Eds.)    ISBN: 978-984-33-8695-3, PI.95 (1-9) leachate passing through the sewage treatment plant concentrate in the sewage sludge making it difficult or dangerous to dispose of to land without incurring a risk to the environment (Kashif et.al., 2011). Leachates may contain large amounts of organic contaminants which can be measured as chemical oxygen demand (COD) and biological oxygen demand (BOD), ammonia, halogenated hydrocarbons suspended solid, significant concentration of heavy metals and inorganic salts. If not treated and safely disposed, landfill leachate could be a potential source of surface and ground water contamination, as it may percolate through soils and sub soils, causing pollution to receiving waters (Li et. al., 2010).   Water tension has become a significant problem all over the world. According to numbers given by WHO (2012), 1.1 billion people of the world do not have improved water and 2.4 billion people do not have any type of improved sanitation facilities. Approximately 3.4 mil-lion people die every year because of water-related diseases which corresponds to almost the whole city of Los Angeles (Prüss-Üstün et al., 2008). The selection of treatment methods are mainly based on specific characteristics of leachate under examination.   Coagulation is an essential process in water and industrial wastewater treatment. Several studies have been reported on the examination of coagulation for the treatment of landfill leachate, aiming at performance optimization, i.e. selection of the most appropriate coagulant, determination of experimental conditions and assessment of pH effect. Aluminum sulfate (alum), poly aluminum chloride (PAC) and ferrous sulfate (FeSO 4 ) were commonly used as coagulants in Bangladesh. Iron salts were proved to be more efficient than aluminum ones, resulting in sufficient chemical oxygen demand (COD) reductions (up to 56%), whereas the corresponding values in case of alum or lime addition were lower (39 or 18%), respectively (Diamadopoulos, 1994). Furthermore, the addition of flocculants together with coagulants may enhance the floc-settling rat (Amokrane and Comel, 1997; Zong ping et al., 2002). The objectives of this study were determination of the characteristics of untreated leachate. The aim was the determination of the most appropriate coagulant type and optimum dose for removing of COD and TSS in leachate and studying of pH effect on removal efficiency. The experimental study was conducted to investigate the coagulation process efficiency for the treatment of leachate. Also the findings in this study were compared with the standard tools available in the literature. Methodology Sample Collection Properly collection of leachate sample has an important role in this study. Firstly Rajbondh landfill site in Khulna city was visited to select sampling station. Leachate is first accumulated from the waste into collection pond. For collection, plastic containers were cleaned with tap water and leachate was collected from collection pond. Air bubbles were removed and the containers were capped immediately. Sampling Method Proper standard collection of leachate samples for analysis is of great importance. Representative samples were tested in the laboratory for the assessment of the existing pollutants and treatment options. The collected samples were transported to the laboratory quickly and then samples were preserved in refrigerator to keep at 4 0 C. All possible efforts were made to minimize the time lag between collection and analysis so that no significant change may occur in the quality of the samples. Large particles and debris were removed to minimize particulate effects in oxidation reactions. Quality Assessment Characteristics of the raw leachate samples were determined through extensive laboratory analysis. The leachate parameters were determined including temperature, pH, color, turbidity, TDS, TS, TSS, DO i , alkalinity, salinity, COD, BOD 5 , electric conductivity, total coliform and feacal coliform.   M. Alamgir, K.A.B.M. Mohiuddin, S.M.T. Islam, and M.H. Hasan (Eds.)    ISBN: 978-984-33-8695-3, PI.95 (1-9) Temperature and pH were determined by the digital pH meter (HACH, Model No. Sension156). The turbidity was measured with an electronic turbidity meter. Color was investigated using spectrophotometer (HACH; DR/2400) according to Standard Methods APHA, AWWA and WEF (1998). Total alkalinity was measured by titration with 0.02N H 2 SO 4 . BOD 5 was measured by incubation in the dark at 20 0 C for 5 days. COD was measured by titration (APHA 1998).Electric conductivity (EC) was determined by EC meter (HACH, model no. sension5). Total suspended and dissolved solids were dried to a constant weight at 105 0 C. The comparison of different parameters of Rajbondh Landfill leachate with Bangladesh standards for discharging treated leachate into inland surface water are given in Table 1. Table 1 Characteristics of raw leachate of Rajbondh landfill and comparison with Bangladesh standards for discharging treated leachate into inland surface water Parameters Unit Raw leachate Bangladesh standards for discharging treated leachate into inland surface water    pH -- 8.6 6-9 DO i  mg/l 0.14 4.5-8 COD mg/l 5760 200 BOD 5  mg/l 142.1 50 BOD 5 /COD -- 0.0247 --  Alkalinity mg/l 1700 -- Salinity mg/l 2800 -- Temperature C 28.7 -- EC μS/cm  5.67 -- TSS mg/l 400 150 TDS mg/l 16600 2100 TS mg/l 17000 -- Turbidity NTU 336 -- Color pt-co 17800 -- TC Nos. 740 -- FC Nos. 300 -- On the basis of this comparison some parameters exceed the range of Bangladesh standards for discharging treated leachate into inland surface water. The treatment should be done for discharging into inland surface to minimize harmful effect on environment. Coagulation process was adopted using the coagulants such as Aluminum Sulphate (Al 2 (SO 4  ) 3 .18H 2 O), Poly-aluminum chloride (PAC) and Ferrous Sulphate (FeSO 4 ). Leachate Treatment The effect of Aluminum Sulphate (Al 2 (SO 4  ) 3 .18H 2 O), Poly-aluminum chloride (PAC) and Ferrous Sulphate (FeSO 4 ) at various dosages on removing the COD and TSS content of leachate were investigated in the physicochemical treatment experiments by using Jar Test apparatus. Firstly, pH of samples were adjusted to desired pH (2, 5, 7 and 9) and then the varying coagulant concentrations (500, 1000, 1500, 2000 and 2500 mg/L) at room temperature (20 o C) were dosed into 1 liter of a leachate sample. The fast mixing (110 rpm) for 3 minutes, slow mixing (50 rpm) for 20 minutes and 30 minutes settling time were applied sequentially in chemical precipitation. After that, the supernatant was analyzed for COD and TSS concentration according to standard methods. The removal efficiency of TSS and COD was obtained by using equation (1) Removal Efficiency (%) = ×100 (1) Where, C 0  and C t are the initial and final concentrations of COD and TSS.   M. Alamgir, K.A.B.M. Mohiuddin, S.M.T. Islam, and M.H. Hasan (Eds.)    ISBN: 978-984-33-8695-3, PI.95 (1-9) Results and Discussion Alum Efficiency The effect of various doses of alum and different pH values on the COD removal efficiency is shown in Figure 1. It is observed that, generally the removal of COD was increased with increasing concentration of added alum. But the removal efficiency was decreased up to 1000 mg/L concentration of alum and further adding alum increased removal efficiency. The high efficiency for COD removal by alum was obtained at pH=9 and 2500 mg/L concentration of alum. Figure 1: The effect of alum doses and pH on the removal of COD concentration in leachate.   The effect of various doses of alum and different pH values on the removal of TSS is shown in Figure 2. Figure shows that removal of TSS was increased with increasing concentration of added alum, except for the concentration of 500 mg/L. The high efficiency for TSS removal by alum was obtained at pH=7 and 2500 mg/L concentration of alum. Figure 2: The effect of alum doses and pH on the removal of TSS concentration in leachate. PAC Efficiency The effect of various doses of PAC and different pH values on the COD removal efficiency is shown in Figure 3. It is observed that, the maximum COD removal efficiency was obtained at pH=7 for 2500 mg/L PAC concentration.   M. Alamgir, K.A.B.M. Mohiuddin, S.M.T. Islam, and M.H. Hasan (Eds.)    ISBN: 978-984-33-8695-3, PI.95 (1-9) Figure 3: The effect of PAC doses and pH on the removal of COD concentration in leachate. The effect of various doses of PAC and different pH values on the removal of TSS is shown in Figure 4. The maximum removal efficiency was found at pH=5 for 2500 mg/L concentration of PAC. Figure 4: The effect of PAC doses and pH on the removal of TSS concentration in leachate. Ferrous Sulphate Efficiency The effect of various doses of FeSO 4  and different pH values on the COD removal efficiency is shown in Figure 5. It is observed that, generally the removal of COD was increased with increasing concentration of added FeSO 4 . But the optimum removal efficiency was found for 2000mg/L concentration of FeSO 4  at pH=7.   Figure 5: The effect of FeSO 4 doses and pH on the removal of COD concentration in leachate.
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