A new study by the Indian Institute of Science (IISc), Bangalore, has found that leachate from landfills is posing a major threat to the environment. Leachate is a contaminated liquid that drains through the bottom of the solid waste disposal facilities such as landfills. It contains numerous dissolved and suspended materials. These materials have a high value of Leachate Pollution Index (LPI) and pose a threat to the environment and human health.
The researchers conducted this study with the aim of understanding the effect of ageing on the characteristics of leachate. They selected a landfill at Terra Firma Biotechnologies Ltd, which is situated at Gundlahalli village in Doddaballapura taluk, near Bangalore. "We collected leachates from two different parts of the site. The first sample was from the location with old waste and sample-II from the location with relatively recent waste," said B P Naveen, a member of the study team and a PhD scholar with the Department of Civil Engineering at IISc.
"We analysed these samples to test the physico-chemical characteristics. We then calculated the LPI of both. LPI is an ascending order scale index used to represent the overall leachate contamination potential of a Municipal Solid Waste landfill," said Naveen.
"This analysis helped us in understanding the age of the waste. We found that the sample-I was more than 10 years old and sample-II was about four to five years old," he added. Analysis showed that the leachate from young, fresh waste is a bigger pollution threat compared to that from old waste. It also indicates that ageing has little effect on reducing the harmfulness of the leachate.
Once the landfill is stabilised, it is usually reclaimed and reused either as a disposal facility or for other purposes. "The rising cost of land, especially in urban areas, has made it necessary to reuse existing or abandoned landfills. Thus, any attempt to reclaim land for development should understand the characterization of waste with their physical and geo-technical properties along with their chemical composition," said Naveen.
During the study, the team observed that composting sites in landfills had no leachate collection and treatment system. This is also a major risk. "Leachate may percolate through subsoil causing pollution to ground water and surface water resources. Our future study will focus on understanding these relationships," he said.