These elevated temperatures in dumpsite can alter gas composition, worsen odours and leachate seeps
A massive fire broke out at Ghazipur landfill in Delhi on April 21, 2024. Photo: Vikas Choudhary / CSE Alarms continue to sound over the Ghazipur landfill site in Delhi after a recent fire outbreak. Now, a new study has emerged highlighting the dangers posed by rising temperatures within its different layers.
The Ghazipur landfill, notorious for its immense size and environmental impact, caught fire on April 21, 2024. The incident blanketed parts of Delhi in toxic smoke, raising health concerns for residents.
Read more: Ghazipur landfill fire: Annual choking hazard for Delhi
High temperatures in the middle layers of the dumpsite are expanding, moving towards the surface, according to the study published in journal Scientific Reports.
“The composition of the input waste must be carefully decided so that the temperature fluctuations are normalised,” the researchers wrote in their paper.
A municipal solid waste (MSW) dumpsite becomes an “elevated temperature landfill” when it reaches higher temperatures than usual — often exceeding 55 degrees Celsius or 62.7°C.
Normally, landfills generate heat as waste decomposes. However, when temperatures rise much higher, it's typically due to unusual chemical reactions within the waste. These abnormal reactions are the main cause of high temperatures in these landfills, according to the United States Environmental Protection Agency.
Elevated temperatures in landfills can cause changes in landfill gas composition, noxious odours, rapid and severe waste settlement, leachate seeps and outbreaks.
Read more: ‘Unscientific’ disposal, treatment of waste behind massive fire at Ghazipur landfill, say experts
MSW typically comprises waste materials originating from homes, businesses, institutions and industries in urban areas. It includes papers, plastics, glasses, metals, food scraps, clothes, yard waste and other miscellaneous waste materials.
In addition to temperature, the study also measured the properties of leachate and its influence on groundwater.
Leachate is a contaminated liquid (containing high concentrations of inorganic ions, organic molecules, and other harmful substances, including heavy metals and ammonia). The biological decomposition of waste in landfills releases gases, heat, and leachate as a by-product.
The toxic leachate, according to the paper, can contaminate nearby water bodies or percolate to reach groundwater.
After taking monthly leachate samples from May 2021 through October 2021, the researchers found that samples were alkaline, indicating an abundance of alkaline compounds. The conductivity value, which represents the presence of salts, was also found to be high.
Read more: Only 7% of total legacy waste in Delhi’s Ghazipur landfill is bio-mined: Report
The team also collected water samples from handpumps and found that water in the wells near the landfill was more alkaline than the distant ones. The conductivity of groundwater was high at the north of the landfill and at the points near the landfill.
The values indicated that the leachate is seeping into the groundwater, the researchers highlighted.
“The alkaline nature of water and high conductivity values near the landfill suggest a severe risk of groundwater pollution,” the researchers wrote in their study.
The team also recorded temperatures at several points in the landfills. Temperature is important to facilitate the biological decomposition of wastes. It should ideally be in the ranges 35-40°C and 50-60°C for two kinds of bacteria involved in breaking down garbage, respectively.
The team also recorded maximum temperatures close to the mid-depths of the landfill. “The Ghazipur landfill can be accepted as an elevated temperature landfill based on the temperature data obtained,” the researchers wrote in the paper.
Read more: Ghazipur, Delhi: Just why has this landfill been simmering for so long
The landfill subsoil could be broadly categorised into three zones based on the temperature.
Zone-1 can be established up to the depth of 30 metres from the surface and has a temperature range of 30-50°C, while Zone-2, which sits between 30 m and 50 m below the surface, witnesses mercury ranging between 60°C and 70 °C.
Zone-3 extends up to a depth of 60 m and is the coolest, where temperatures stay below 30 °C.
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