Toxicity analysis and public health aspects of municipal landfill leachate: a case study of Okhla landfill, Delhi Vijaya Singh A.K. Mittal WWW-YES-2009
Contents � Introduction Scenario of landfilling in India – Leachate: why it is cause of concern? – Bioassay for toxicity analysis – Site details – � Methodology and Experimental Set-up Leachate characterization and toxicity analysis – Fish bioassay set-up – WWW-YES-2009 � Analysis of Results � Conclusions
Introduction � Landfilling is the most common form of municipal solid waste (MSW) disposal in India � Daily MSW generation in Delhi is approx.7000 metric tons � Monthly leachate production WWW-YES-2009 estimated to be 81.5 m 3
Introduction What is leachate and why it is cause of concern? Leachate is defined as liquid that has percolated through solid waste � and has extracted dissolved constituents of waste, soluble products of waste degradation process and suspended materials from it. Studies have shown that � leachate from MSW landfill can be more toxic than hazardous waste landfill leachate Leachate seeping out of landfill � is a threat to: WWW-YES-2009 Ground water – Surface water –
Introduction Bioassay toxicity test Bioassay � Chemical analysis : Identifies the presence of – specific compounds Acute Chronic Not enough to assess – the potential danger Evaluation takes longer Evaluation in short time � Bioassay toxicity test : since sub-lethal effects (mortality is the end point) must be analyzed Duration: Duration: 7-30 days Can detect toxicity even 24 h – 96 h – (exposure for at least 1/10 th of lifetime when the contaminants Relates concentration to are not identified time of death for a Effect of concentration particular test organism WWW-YES-2009 on growth, reproduction, behavioral, physiological Most frequently used Reflect the cumulative – or biological functions (short = less expensive) and synergistic effects of all the compounds
Introduction Delhi landfills At present there are 3 landfill � sites in Delhi – Okhla, Gazipur and Bhalsawa � Category: uncontrolled solid waste disposal facility No base liners – No gas or leachate collection – system Leachate percolates down the � WWW-YES-2009 ground surface, gets collected in low lying area, sometimes mixed Adopted from Zafar and Alappat, (2004 ) up with sewer or drainage system
Okhla landfill site Okhla landfill site � Commissioned in 1996 � Waste type: domestic waste (e.g. kitchen waste; paper, plastic, glass, cardboard and clothes), construction waste and unauthorized industrial waste WWW-YES-2009 � Waste density: 1200 kg/m 3
Leachate finds its way through an opening at the low lying area of the landfill Leachate flowing freely on the ground WWW-YES-2009
Leachate sampling points WWW-YES-2009
residential area Leachate from flowing in the Okhla landfill premises of adjacent WWW-YES-2009
Methodology: Leachate Characteristics Parameters Range of Leachate samples used in the � values a fish bioassay were collected in the month of June and pH 7.6 – 8.2 December 2007 Alkalinity 12,000 – 32,000 Samples were always collected Hardness 9,000 – 25,000 � from 2 different places of the Chloride 16,000 – 23,000 landfill site, namely; COD 6,000 – 20,000 L1 & L2 collected in June L1 & L2 collected in December NH3-N 1,000 – 3,000 TSS 20,000 – 35,000 The characteristics of leachate � WWW-YES-2009 TDS 2,000 – 19,000 varied significantly with space and time TS 24,000 – 54,000 a All in mg/l except pH
Methodology: leachate toxicity Acute toxicity (LC50) of leachate was determined using static 96 h � fish bioassay LC50: Lethal concentration that causes death for 50% of test � organisms Calculation method: � Spearman-Karber method Test organism: � Poecilia reticulata (guppy fish) WWW-YES-2009
Set-up for toxicity testing Range finding tests: � conducted prior to 96h acute toxicity tests Contro l X 2 % X 1 % X = Concentration of � leachate in test solution (% v/v) No. of test sp. In each � X 3 % X 4 % X 5 % container = 10 (mean wt. 0.2 – 0.4 g) WWW-YES-2009
Results: Leachate toxicity 120 96-h LC50 = <12% 100 96-h LC50 = <13% 100 80 Mortality % Mortality % 80 60 60 40 40 20 20 0 0 -20 -20 10.0% 11.5% 13.0% 14.5% 15.5% 16.0% 7.5% 9.0% 12.0% 13.5% 15.0% 16.5% Dilution of samples Dilution of samples Toxicity assay L1 June 2007 Toxicity assay L2 June 2007 120 96-h LC50 = <4% 96-h LC50 = <3% 120 100 100 Mortality % 80 Mortality % 80 60 60 40 40 20 20 WWW-YES-2009 0 0 -20 -20 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% 0.5% 1.5% 3.0% 4.5% 6.0% 7.5% Dilution of samples Dilution of samples Toxicity assay L2 December 2007 Toxicity assay L1 December 2007
Results: Metals in the leachate Metals deemed as hazardous to � Metals Range of environment and public health were values a detected Lead (Pb) 0.9 – 1.5 Non biodegradable and do accumulate � in the food web Cadmium (Cd) 0.2 - 0.4 Copper (Cu) 0.2 - 1.5 Pb – potential carcinogen, affects � nervous system Manganese (Mn) 0.2 - 0.5 Cd – carcinogen, affects hormone and � Zinc (Zn) 0.8 – 1.5 enzyme system Chromium (Cr) 0.8 – 2.2 Ni – carcinogen � Iron (Fe) 4.0 – 9.5 Co, Cr, Zn and Cu – have been Nickel (Ni) 1.0 – 5.0 � WWW-YES-2009 reported for various health problems Cobalt (Co) 0.3 – 1.0 Fe and Ni – highest concentrarion in � a All values in mg/L all the four leachate samples
Organic compounds, toxicity and bioavailability � Landfill age >10 years : leachate may contain countless number of organic compounds � Organo-nitrogenated substances & heavy metals : Highly toxic – High potential of bioavailability – � Organo-halogenated compounds : can persist in aquatic environment and cause bioaccumulation � Factors affecting bioavailability : WWW-YES-2009 pH – Ion exchange capacity – Water solubility –
Conclusions � The study shows a clear cut case of potential environmental pollution as indicated by the toxicity of Okhla leachate � No correlation was observed in the toxicological and physicochemical parameters of leachate � Presence of heavy metals in leachate supports the toxicity data � Ecotoxicological evaluation of leachate is fundamental for WWW-YES-2009 assessing the risk posed to environment and public health
Thank you !!! WWW-YES-2009
Recommend
More recommend
