Effects of Leachate on Groundwater

There can be serious effects of leachate on groundwater: A release of leachate to the groundwater may present several risks to human health and the environment. The release of hazardous and nonhazardous components of leachate may render an aquifer unusable for drinking-water purposes and other uses.

Toxic sewer leachate illustrated to show the effects of leachate on groundwater and surface water.
CC BY-ND by sharmainedebordeaux1

Leachate impacts to groundwater may also present a danger to the environment and to aquatic species if the leachate-contaminated groundwater plume discharges to wetlands or streams.

Once leachate is formed and is released to the groundwater environment, it will migrate downward through the unsaturated zone until it eventually reaches the saturated zone . Leachate then will follow the hydraulic gradient of the groundwater system.

Monitoring wells at landfills allow scientists to determine whether contaminants in leachate are escaping into the local groundwater system. The wells are placed downgradient of the landfill at appropriate depths and at various intervals to intercept any contaminants and monitor their movement. via waterencyclopedia.com

Factors in Assessing the Groundwater Contamination Risk for a Landfill

The risk of groundwater contamination by any leachate that is not caught by collection systems is determined by the following factors.

• Concentration of contaminants.

• Permeability of the geologic strata.

• Type of geologic strata.

• The toxicity of the contaminants.

The direction of groundwater flow.Areas near landfills have a greater possibility of groundwater contamination because of the potential pollution source of leachate originating from the nearby site. Such contamination of groundwater resource poses a substantial risk to local resource user and to the natural environment. The impact of landfill leachate on the surface and groundwater has given rise to a number of studies in recent years. (Suman Mor etc2005)

Leachate Release and Migration

The presence of contaminants in groundwater particularly near the landfill sites warns its quality and thus renders the associated aquifer unreliable for domestic water supply and other uses. Although some remedial measures are suggested to reduce further groundwater contamination via leachate percolation, the present study demands for the proper management of waste in Erode city.

Landfills have been identified as one of the major threats to groundwater resources not only in India but throughout the world.

More than 90% of the Municipal Solid Waste (MSW) generated in India is directly dumped on land in an unsatisfactory manner. The solid waste placed in landfills or open dumps are subjected to either groundwater underflow or infiltration from precipitation or any other possibility of infiltration of water. During rainfall, the dumped solid wastes receivers water and the by-products of its decomposition move into the water through the waste deposition.

The liquid containing innumerable organic and inorganic compounds is called ‘leachate’. This leachate accumulates at the bottom of the landfill and percolates through the soil and reaches the groundwater.

Areas near landfills have a greater possibility of groundwater contamination because of the potential pollution source of leachate originating from the nearby dumping site. Such contamination of groundwater results in a substantial risk to local groundwater resource user and to the natural environment. The impact of landfill leachate on the surface and groundwater has given rise to a number of studies in recent years and gained major importance due to drastic increase in population. There are many approaches that can be used to assess the groundwater and surface water contamination.

It can be assessed either by the experimental determination of the impurities or their estimation through mathematical modeling. via nih.gov

Chemicals in Leachate Which Contaminate Groundwater

It contain high levels of organic, inorganic, heavy metal, and xenobiotics, which percolates through the subsoil and contaminate the groundwater. To assess the effect of landfills on groundwater, various physicochemical parameters including heavy metals, and microbiological examination of leachate and groundwater samples was conducted. The results obtained were compared with Bureau of India Standards and World Health Organization guidelines. via springer.com

Actual Results for Leachate in Groundwater

Concentrations of various physicochemical parameters including heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, Fe and Zn) were determined in leachate samples and are reported.

The concentrations of Cl-, NO3 -, SO4 2-, NH4 + were found to be in considerable levels in the groundwater samples particularly near to the landfill sites, likely indicating that groundwater quality is being significantly affected by leachate percolation.

Further they were proved to be the tracers for groundwater contamination near Semur and Vendipalayam dumpyards. The presence of contaminants in groundwater particularly near the landfill sites warns its quality and thus renders the associated aquifer unreliable for domestic water supply and other uses.

Although some remedial measures are suggested to reduce further groundwater contamination via leachate percolation, the present study demands for the proper management of waste. via researchgate.net

Compositions for Leachate Contamination

Compositions of landfill leachate and groundwater pollution were studied at industrial sites landfill, which are located at Ota, Nigeria. The leachate was sampled at 5 different locations at the landfill, and at 15 and 20 m downstream of the landfill.

Groundwater samples were collected from 10 different sources to study the possible impact of leachate percolation into the groundwater. The leachate and groundwater samples were collected during wet season, due to the excessive generation of leachate during this season. via ajol.info

Dump Water Exceeding WHO and EPA Limits

For the leachate polluted groundwater certain parameters exceeded the WHO and EPA limits. These parameters included conductivity, total dissolved solids, chlorides, sulfates, Mn and Fe. The results suggested the need for adjusting factors enhancing anaerobic biodegradation that lead to leachate stabilization in addition to continuous monitoring of the groundwater and leachate treatment processes. via sciencedirect.com

Pollution Index (LPI)

Leachate pollution index (LPI) of landfill leachate was evaluated with their physicochemical analysis that represents the overall leachate pollution potential and hazardous nature of MSW leachate.

Physicochemical analysis of groundwater quality around the landfill site does not favour to drinking and domestic purposes as per the WHO and BIS standard.

A considerable amount of NO3, PO43−, Fe, electrical conductivity (EC) and total dissolved solid (TDS) were found in the groundwater samples near to the landfill site especially during post-monsoon, indicating that groundwater quality is being significantly affected by leachate percolation. via sciencedirect.com

Possible Contaminants and their Impact on Surface and Groundwater

The leachate contamination of soils has a significant impact on the quality of the soil. According to Magaji , soil is in most cases the most polluted part of the ecosystem around landfills, because chemical elements are transported and distributed when water seeps through it.

Several pollutants, including heavy metals, polyaromatic hydrocarbons, and pharmaceutical compounds accumulate in the soil. According to Shaikh et al. The implication associated with these pollutants, especially heavy metal contamination, is of concern in agricultural production systems.

Leachate emanating from landfills built without engineered liners and leachate collection systems could impact negatively on surface water and groundwater quality with severe consequences for human and ecosystem health. via mdpi.com

Conclusion

Groundwater pollution is mainly due to the process of industrialization and urbanization that has progressively developed over time without any regard for environmental consequences.

Areas near landfills have a greater possibility of groundwater contamination because of the potential pollution source of leachate originating from the nearby site.  via scialert.net

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