Tambaram takes bio-route to clear toxic dump yard
CHENNAI: After years of struggle by local residents, Tambaram Municipality has finally planned to clear the Kannadapalayam dumpyard using the biomining method. The civic body has switched to the new technology, which officials believe is much more efficient and the land would almost return to it original form.
Besides, the municipality has started implementing ‘Wednesday scheme’ to segregate degradable and non-degradable wastes at the source itself.The move has come after the National Green Tribunal pulled up the civic body over environmental hazards caused by the dumpyard and ordered its removal. “We initially planned to convert it (the garbage hill) into a small garden. But we have changed the plans opting for biomining,” says Albert Arulraj, sanitary inspector in charge of the dumpyard.
The process
“Biomining process is a popular solution for huge landfills,” says Nagesh Prabhu, director of Zigma Global Environ. While explaining the process, he adds that “it is a near zero emission process where the dump-hills can be cleared as if they never existed.”
He said a set of machinery would be set up near the garbage hill to segregate the combustible and non-combustible materials with an automatic machine. He shattered the myth that the dump will be cleared soon after the machinery is set up.
This is mainly on account of the fact that dumpyards are complex. They contain methane, and other harmful gases since they have been there for many years. There is also water pollution caused by ‘leachate’ which is produced from garbage decay. “If you let a earthmover to climb over the garbage hill and simply open it, there is a chance that these gases might escape in a rush. Sometimes it might cause fire accidents and there is a probability that those working in the dumpyard will feel nauseous,” he warns. Hence, the process starts with pre-stabilisation where bio-culture is sprayed. Bio-culture is basically bacteria which will rapidly degrade the material that is not fully bio-degraded. It will stabilise the dump, which includes sanitising it, freeing it from pathogens and making it free of ammonia, methane, hydrogen sulphide and other obnoxious gases.
Waste is segregated by a machine and combustible materials like plastic and wood sent to cement factories to be used as alternate fuel. But one might ask, “Will the burning plastic not produce air pollution?”According to norms, the smoke emitted by burning a material in the cement furnace at 90 degree C as alternate fuel will be sent through a scrubber (an air filter), which will absorb all the poisonous substance of the gases. The non-combustible materials like sand, soil and other degraded food waste will be dumped again in the given land as they can easily decay and maintain the carbon content.
“There is carbon content in the soil, which we receive through food and we give it back through wastes,” said the director of one of the companies involved in bio-mining. “This routine is damaged once you start to incinerate the garbage. The carbon content is depleted too much and also produces air pollution. But by bio-mining, the required carbon is given back to the earth. Though the process is simple, it’s highly scientific.”The sanitary inspector said the 1.5 lakh tonne garbage heap in 2.3 acre land will be cleared within a year. The tender has been issued and they are waiting to finalise the contractor, after which garbage will be removed.
Transfer station
To prevent building up of another garbage hill, the Tambaram municipality has started segregating wastes and convert ing degradable waste into manure and raw materials for industries. A total of 110 tonnes of waste is collected everyday and brought to a transfer station by the municipal workers and is then taken to the Vengadamangalam treatment plant by the Essel Group.
“The Municipal Solid Waste (MSW) processing plant collects 280-300 tonnes of municipal garbage on a daily basis,” said RM Manikandan, plant head of the SPV Pallavaram and Tambaram Private Ltd, of the Essel Group. “The fresh garbage is led into a primary shredder machine and the objects are broken down to 300mm and passed on to the drier to remove the moisture.”
This is then led to the first inspection table, where big particles like stone, plastic bottles and glasses are separated using manpower. The particles then pass through a disc screen separator, where the materials below 20mm will go to fine screen for further separation and those above 20 mm will enter magnetic Eddy current separator.
The final product of the plant consists of manure, scrap materials and fuel for cement plants.
The plant is in its next phase of development. The company might produce 4.5 megawatt power from the wastes, which requires ` 55 crore investment.
Kumbakonam example
Kumbakonam was one of the first places to implement biomining process. “We were able to reclaim almost 10 acres of land which we thought we would never get back,” said the Kumbakonam municipality commissioner K Uma Maheshwari. “The bio-mining process went on from Sept 2015 to Feb 2017 to reclaim 1,31,000 cubic metre by which we got 80 per cent of the total land and the process for the other 20 per cent (58,000 cubic metre) is going on.”
Bring on the bacteria...
Bio-culture is basically bacteria which will rapidly degrade the material that is not fully degradable. It will stabilise the dump, including sanitising, freeing it from pathogens and making it free from ammonia, methane, hydrogen sulphide and other obnoxious gases.
Generally the moisture content inside a dumpyard would be 60 per cent whereas it is only 15 per cent in a normal environment. The bio-culture will bring it down to 15 per cent.
Dumpyards that have had years-old plastic, wood and food waste will be difficult to segregate. Further, methane and other obnoxious gases that produce leachate liquid will also be present. Bio-culture will stop the leachate liquid and make the inside of dumps dry.
For the Kannadapalayam dump hill, pre-stabilisation will take almost three months.
The stabilised dump-hill will then be cleared layer-by-layer so as to let methane and other obnoxious gases escape without harming people working at the site.
Wednesday scheme
The Tambaram municipality is following the Tirunelveli and Tiruchirapalli corporations which had introduced the ‘Wednesday scheme.’ The residents have to keep one week’s non bio-degradable waste such as used plastic bottles, glasses, plastic items and others outside or inside their houses.
Designated members would collect this and give it to the recycling agents and the money generated is shared among the workers.
Sanitary inspector Albert Arulraj is hopeful that people will eventually get used to segregating bio-degradable wastes from others at their homes.