Toxicity analysis and public health aspects of municipal landfill - - PowerPoint PPT Presentation

Toxicity analysis and public health aspects of municipal landfill leachate: a case study of Okhla landfill, Delhi

Vijaya Singh A.K. Mittal

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Contents

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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

Analysis of Results Conclusions

Introduction

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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

estimated to be 81.5 m3

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:

–

Ground water

–

Surface water

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Introduction

Bioassay toxicity test

Chemical analysis:

–

Identifies the presence of specific compounds

–

Not enough to assess the potential danger

Bioassay toxicity test:

–

Can detect toxicity even when the contaminants are not identified

–

Reflect the cumulative and synergistic effects of all the compounds

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Evaluation in short time (mortality is the end point) Duration: 24 h – 96 h Relates concentration to time of death for a particular test organism Most frequently used (short = less expensive) Evaluation takes longer since sub-lethal effects must be analyzed Duration: 7-30 days (exposure for at least 1/10th of lifetime Effect of concentration

• n growth, reproduction,

behavioral, physiological

• r biological functions

Acute Chronic

Bioassay

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

ground surface, gets collected in low lying area, sometimes mixed up with sewer or drainage system

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Introduction

Adopted from Zafar and Alappat, (2004)

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

Waste density: 1200 kg/m3

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Okhla landfill site

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Leachate finds its way through an opening at the low lying area

• f the landfill

Leachate flowing freely on the ground

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Leachate sampling points

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Leachate from Okhla landfill flowing in the premises of adjacent residential area

Methodology: Leachate Characteristics

• Leachate samples used in the

fish bioassay were collected in the month of June and December 2007

• Samples were always collected

from 2 different places of the landfill site, namely; L1 & L2 collected in June L1 & L2 collected in December

• The characteristics of leachate

varied significantly with space and time

24,000 – 54,000 TS 2,000 – 19,000 TDS 20,000 – 35,000 TSS 1,000 – 3,000 NH3-N 6,000 – 20,000 COD 16,000 – 23,000 Chloride 9,000 – 25,000 Hardness 12,000 – 32,000 Alkalinity 7.6 – 8.2 pH

Range of valuesa Parameters

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aAll 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
• rganisms
• Calculation method:

Spearman-Karber method

• Test organism:

Poecilia reticulata (guppy fish)

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Set-up for toxicity testing

• Range finding tests:

conducted prior to 96h acute toxicity tests

• X = Concentration of

leachate in test solution (% v/v)

• No. of test sp. In each

container = 10 (mean

• wt. 0.2 – 0.4 g)

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Control

X1% X2% X3% X4% X5%

Results: Leachate toxicity

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• 20

20 40 60 80 100 7.5% 9.0% 12.0% 13.5% 15.0% 16.5% Dilution of samples Mortality %

96-h LC50 = <13%

• 20

20 40 60 80 100 120 10.0% 11.5% 13.0% 14.5% 15.5% 16.0% Dilution of samples Mortality %

96-h LC50 = <12%

• 20

20 40 60 80 100 120 0.5% 1.5% 3.0% 4.5% 6.0% 7.5% Dilution of samples Mortality %

96-h LC50 = <3%

• 20

20 40 60 80 100 120 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% Dilution of samples Mortality %

96-h LC50 = <4%

Toxicity assay L1 June 2007 Toxicity assay L2 June 2007 Toxicity assay L1 December 2007 Toxicity assay L2 December 2007

Results: Metals in the leachate

• Metals deemed as hazardous to

environment and public health were detected

• Non biodegradable and do accumulate

in the food web

• Pb – potential carcinogen, affects

nervous system

• Cd – carcinogen, affects hormone and

enzyme system

• Ni – carcinogen
• Co, Cr, Zn and Cu – have been

reported for various health problems

• Fe and Ni – highest concentrarion in

all the four leachate samples

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0.3 – 1.0 Cobalt (Co) 1.0 – 5.0 Nickel (Ni) 4.0 – 9.5 Iron (Fe) 0.8 – 2.2 Chromium (Cr) 0.8 – 1.5 Zinc (Zn) 0.2 - 0.5 Manganese (Mn) 0.2 - 1.5 Copper (Cu) 0.2 - 0.4 Cadmium (Cd) 0.9 – 1.5 Lead (Pb)

Range of valuesa Metals

aAll values in mg/L

Organic compounds, toxicity and bioavailability

Landfill age >10 years: leachate may contain countless number of

• rganic 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:

–

pH

–

Ion exchange capacity

–

Water solubility

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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

assessing the risk posed to environment and public health

Conclusions

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Thank you !!!