Fine soil-like materials recovered from legacy dumpsites may contain contaminants and should thus be tested before used in any application
Photo: iStock Legacy waste dumpsites are a major environmental problem in India. The country has more than 3,000 of them and they contain millions of tonnes of waste.
As reflected on the Swachh Bharat Mission Urban dashboard, there is around 230 million tonnes of legacy waste covering an area of 20,937 acres in India that needs urgent intervention. This waste can pose a serious threat to public health and the environment.
In the last few years, dumpsite remediation by biomining has gained significant momentum due to the potential for resource recovery from landfills. However, it is important to note that landfills primarily contain fine soil-like material (FSLM), which typically has little to no economic value.
Biomining of legacy waste dumpsites generates waste fractions such as segregated combustible materials (SCF) consisting of plastics, textiles, leather, wood, among others; construction and demolition waste (C&D waste); and FSLM, typically comprising particles smaller than 6 mm, once the larger waste pieces have been removed.
The scientific application of FSLM ranges from road construction to land reclamation and as a filler material for low-lying areas. However, given the fact that they are recovered from historically contaminated sites having mixed garbage, scientific testing and assessment are critical prior to its usage in gainful applications. This includes physical and chemical properties, identifying potential contaminants and ensuring compliance with environmental regulations.
As specified in the Central Pollution Control Board guidelines for the disposal of legacy waste (2019), fine materials in the size range of 4-6 millimetres are referred to as ‘bio-earth’ or ‘good earth’ material, which can be utilised by farmers as a soil enricher, provided they comply with the Fertilizer Control Order standards. However, in most of the cases, the fine-soil like material excavated from the legacy waste dumpsites do not comply with the standards.
The fine soil-like material can also be used as a filler material for low-lying areas. However, the CPCB guidelines do not provide specific information regarding the parameters that should be tested or the threshold limits, particularly for the presence of toxic metals.
FSLM from legacy waste dumpsites may contain contaminants such as heavy metals and organic pollutants. These contaminants can be harmful to human health and the environment, making it It is important to test FSLM before applying it anywhere.
FSLM from legacy waste dumpsites can be used in a variety of ways, including:
In 2015, the Union Ministry of Environment, Forest and Climate Change launched a transformative initiative — the National Program for Rehabilitation of Polluted Sites. At its core lies the comprehensive "Guidance document for assessment and remediation of contaminated sites in India", serving as a roadmap for tackling the pressing issue of environmental pollution due to comminated sites.
The “Guidance document for assessment and remediation of contaminated sites in India" (2015) sets clear boundaries for acceptable levels of heavy metals and toxic contaminants through two key sets of standards: Environmental Quality Standards (EQS) and Threshold Limit Values (TLV). These standards can be utilised for assessing the gainful application of FSLM recovered from legacy waste dumpsites in India. MoEFCC has mentioned standards of heavy metals in the contaminated sites which are listed below:
| Metal | Hazardous waste levels (levels Schedule II, HW Rules, 2016) 1 | Soil (screening and response levels) | ||||
|---|---|---|---|---|---|---|
| Response levels (Dutch Intervention levels) 2) | Screening levels Soil Quality Guidelines for the Protection of Environmental and Human Health 3 | |||||
| Agricultural | Residential /Parkland | Commercial | Industrial | |||
| mg/l | mg/kg | mg/kg | mg/kg | mg/kg | mg/kg | |
| Arsenic | 5 | 50 (76) | 12 | 12 | 12 | 12 |
| Cadmium | 1 | 13 | 1,4 | 10 | 22 | 22 |
| Chromium (total) | 5 | 64 | 64 | 87 | 87 | |
| Chromium (Hexavalent) Cr(VI) | 50(78) | 0,4 | 0,4 | 1,4 | 1,4 | |
| Chromium (trivalent) Cr(III)) | 180 | - | - | - | - | |
| Copper | 25 | 190 | 63 | 63 | 91 | 91 |
| Lead | 5 | 530 | 70 | 140 | 260 | 600 |
| Mercury | 0.2 | 36 | 6,6 | 6,6 | 24 | 50 |
| Nickel | 20 | 100 | 50 | 50 | 50 | 50 |
| Zinc | 250 | 720 | 200 | 200 | 360 | 360 |
Source: MoEFCC (2015) National Program for Rehabilitation of Polluted Sites in India, guidance document for assessment and remediation of contaminated sites in India
In addition, organic contaminants shall also be tested. MoEFCC (2015) also provides threshold values for organic contaminants such as Dichloro diphenyl trichloroethane (DDT Total) 2,2-Bis(p-chlorophenyl)- 1,1,1-trichloroethane – 50 mg/L, Halogenated aliphatic compounds – 5000 mg/L, Chlorinated phenols – 50 mi/L, Dieldrin – 50 mg/L, among others.
In many cities In India, FSLM recovered from legacy waste dumpsite remediation is used as a filler material for low-lying areas, without testing it for the presence of toxic metals and organic contaminants posing long-term environmental hazards. Heavy metal contamination is a significant risk associated with the use of untested FSLM.
Toxic metals, such as lead, mercury, cadmium, and arsenic, can have detrimental effects on human health. Exposure to these metals through ingestion, inhalation or dermal contact can lead to various health problems, including neurological disorders, organ damage and even cancer.
Additionally, heavy metals have the potential to accumulate in plants and animals. This can lead to bioaccumulation, where the metals move up the food chain. Eventually, humans may be exposed to these contaminants, posing a threat to food safety and public health.
The leachability test of FSLM for the presence of toxic metals is crucial to prevent contamination of adjoining areas when used as a filler material. Ideally, before using FSLM in any application, it is essential to subject it to testing to ensure adherence to relevant country-specific soil standards or other standards available (in this case, MoEFCC 2015 guidelines can be referred to). This guarantees that the material is safe for use, minimizing the risk of long-term environmental hazards and protecting both the environment and human health from the adverse effects of toxic contaminants.
In addition, policy intervention is necessary in this regard to establish clear standards for testing the soil after dumpsite remediation. The state pollution control boards should conduct robust monitoring of sites post dumpsite remediation to ensure compliance with the existing standards.
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