Almost a decade back, when an environmental group raised the red flag over the landfill at Mavallipura, a village about 20 kms north of Bangalore, it marked a new awareness of the harmful fallout of unplanned landfills. Reports suggest that the owner who leased out the land for the landfill actually did not own it at all, and the land was in fact forest land. The Bangalore Municipal Corporation quickly cancelled that agreement but the harm was already done.
In the monumental problem of landfills facing the country, the issue is not just the lack of proper sites but more significantly, the correct system of setting it up and preventing and tackling the ill effects of waste percolating into the land.
Landfill sites
Landfills are essentially mountains of municipal solid waste (MSW) that are collected and gathered from various parts of a city and disposed off in the landfill sites. In India, this waste is mixed - an unruly combination of organic (wet) waste, inorganic (dry items like glass, plastic, etc) waste and debris from construction sites, etc. While the MSW (Management and Handling) Rules are in place and have been so since 2000, not much attention has been paid to the parameters that the rules state must be taken into consideration before dumping waste in landfill sites.
One of the main parameters is the segregation of waste at source. With the increasing understanding that waste is a resource, waste must be segregated at source. Waste generally generated in an Indian household comprises around 70 percent wet waste while the rest 30 percent comprises paper, plastics, glass and metals. Each type of waste has its own function and characteristics. For instance, wet waste when biodegraded can be used to create biogas and compost for agricultural purposes. In fact, it is one of the most fertile kinds of manure that can also make barren lands fertile. Dry waste is, on the other hand, recyclable to an extent. Paper and glass can be recycled and reused; recycled plastic is increasingly finding its place in roads and other similar practices; debris, too, can be powdered and used to make bricks and other similar construction materials. Given this, the segregation of waste at source not only aids in making these processes easier and allows faster recycling and treatment, but also retains its original value, and most importantly, saves space and helps protect the environment and the health of the citizens.
But, what about the existing landfills in the country? The waste that towers over the cities using up precious land and airspace? Technologies over time have been invented and used to reduce the hazardous effects of landfills on the environment.
Leachate treatment
When tonnes of waste are piled one upon the other to reach great heights, it is but natural that the pressure on the lowest portion of the mountain is the greatest. Now, when mixed waste is dumped unceremoniously in ‘scientific’ landfill sites, it is important, as mentioned earlier, for there to be a system to collect both the leachate and the landfill gas.
Leachate is highly complex and polluted wastewater that is produced by the wet waste mixed with other waste when dumped at the landfill site. As the pressure on the waste increases, highly toxic wastewater is released as though it is being squeezed out and slowly enters the ground thus polluting the water table almost irreversibly. Over the years, several leachate treatment technologies like coagulation-flocculation, adsorption by activated carbon, biological treatment and reverse osmosis have been introduced and applied depending, of course, on the conditions available at the landfill site.
However, as Partha Sarathi Majumder, Sr. Manager- Technology, Ion Exchange (India) Ltd., informs, leachate treatment projects in India are far and few between. The treatment of leachate is much like that of waste water; however, the specific process depends on the characteristics of this highly complex solution. Leachate mostly comprises inorganic gaseous pollutants like methane, ammonia, hydrogen sulphide; organic pollutants; nutrients like total nitrogen and total phosphorous; total dissolved inorganic solids like sodium chloride, sodium sulphate/calcium chloride, calcium sulphate. Given these characteristics, any leachate treatment plant must be customised to take not only the load of the maximum amount of leachate that the particular landfill can produce but must also be protected from the effects of its highly corrosive material right from the underground drains to the outlet pipe.
Once the leachate is transported from the landfill site, it reaches a collection pit that is part of the landfill system where it is stored and then transported to a treatment plant either on or offsite according to the characteristics of the leachate. The duration of collection depends on how much leachate is generated and the capacity of the plant. The primary phase of treatment starts with the equalisation tank, which balances the flow and characteristics of the leachate to suit the specifications of the plant. Within around 10-15 days, the leachate collected is tested, analysed and balanced out before going to the next phase of treatment. If the total dissolved solids (TDS) are high, then they can be removed using clarifiers or dissolved floatation systems. The treated water is then collected through a pipe and then sent to the next chamber.
This is where the main biological treatment takes place to remove the organic content. Majumder informs that Ion Exchange uses fluidised media reactor (FMR) technology, which is an aerobic process (provides oxygen). Here, a medium is introduced into the solution to allow the sludge to attach to it. This converts the sludge into carbon dioxide and water. The treated water then moves on to tertiary treatment. Here, another process is the anaerobic process, which produces methane and carbon dioxide that can be used to convert waste to energy. Moreover, it requires lesser power and is thus a green technology. However, it is not effective enough to bring the BOD and COD to the desired levels, hence Majumder prescribes a combination of the two processes. If enough methane is generated, it can be used to create energy or else it is burnt through the flare system.
By the time the water reaches the tertiary system, it is ready to be disinfected. If the total suspended solids are high, it also goes in for filtration using sand and activated carbon filters. And finally, once the outlet water meets the acceptable standards, it is released in its most harmless state into the water system. Of course, this water can be reused and recycled as grey water as well.
Landfill gas recovery
While this is one of the most effective processes to take care of leachate treatment, the landfill continuously and simultaneously releases noxious gases into the air, of which equal amounts of methane and carbon dioxide are a part, along with other non-methane organic compounds. Methane can singularly add to the depletion of the already depleting ozone layer in the earth’s atmosphere. Moreover, apart from the health hazards that it causes to people living in the vicinity and ragpickers working on the site, the gas is highly combustible and can also cause explosions and fires in the worst-case scenario.
As a result landfill gas (LFG) recovery is a rather important step. Not only does it help to reduce odours and other hazards associated with LFG emissions but also prevents methane from infiltrating the atmosphere and contributing to smog and global climate change. LFG is extracted from landfills using a series of wells and a blower/flare (or vacuum) system. This system directs the collected gas to a central point where it can be processed and treated depending upon the ultimate use for the gas. From this point, the gas can be simply flared or used to generate electricity, replace fossil fuels in industrial and manufacturing operations, fuel greenhouse operations, or be upgraded to pipeline quality gas. It can also be used directly in place of other fuels or evaporate leachate. Moreover, it can be used for cogeneration projects to generate both electricity and thermal energy in the form of steam or hot water.
In India, one of the few proposed LFG recovery projects was in the capital of the country at the Okhla landfill site. Here, in 2011-2012, a team comprising officials from TERI, JMI and MoEF proposed a landfill gas recovery plan. According to Dr. Suneel Pandey, Senior Fellow, Earth Science and Climate, TERI, “The Okhla project was an R&D-based demonstration project supported by MoEF, where the landfill gas and its recovery was being monitored. The three-year project demonstrated the feasibility of harvesting landfill gas from large open waste dumps in India before they are closed and redeveloped.”
In this technology, gas wells are put in the landfill with a blower to extract landfill gas. The extracted gas is purified to remove hydrogen sulphide by scrubbing with alkaline waste and is then chilled to remove moisture before the gas can be used either for thermal applications or for power. Unfortunately, despite the success of the technology, after the project and technology were monitored and approved, the set was dismantled on request of the landfill in-charge – the Municipal Corporation of Delhi – since it claimed to need the space for disposal of waste. However, TERI proposes to continue LFG recovery at a commercial level in landfills across the country, while organisations like GAIL have been trying LFG recovery at the Ghazipur landfill in New Delhi.
Reducing landfills
Despite the various technologies to prevent the rather polluting effects of landfills, it is not difficult to completely prevent the dumping of waste. In fact, the need for landfills of such heights is almost obsolete.
According to Rishi Aggarwal, Environmental Activist and Research Fellow at Observer Research Foundation, the approach towards reducing landfills is two pronged. First, the government must stop dumping waste and adding to the pressure of the landfills. While this is a gradual process, it is quite effective. Segregation of waste at source goes hand in hand with this, where the segregated garbage directly goes for treatment and recycling and then reuse. Finally, he says, one needs integrity, awareness and a desire to improve the situation!
Mumbai in particular has around three active landfill sites at Deonar, Kanjurmarg and Mulund. But, previously Chincholi – where the ever famous Mindspace and Inorbit Mall stand today – was also a dumping yard, as was Gorai. In the case of Gorai, the landfill was having adverse effects on the health of the people and the land itself. Moreover, the then-government decided to manage the landfill sites on the basis of a Public-Private-Partnership Model. So, an entire exercise was carried out where a part bio-remediation and part-capping was done. In terms of bio-remediation, biomining and bioenzymes were experimented with. In biomining, the mountains of waste were treated using biological organisms which helped degrade the wet waste leaving behind the dry, inorganic waste, which was then sent for recycling. The process did not take long and was done at a rather low cost. However, after the successful biomining of a part of the land, it was decided that the rest of the waste would be capped and closed. In that, a geo-textile membrane would be used to completely enclose the waste to prevent it from releasing any LFG or leachate. However, now studies show that the trash is releasing methane into the air.
Agarwal says, “The bio-mining model has no leachate or odour. In fact, once the land is flattened, it can be used as additional space for ragpickers to segregate waste, and process both debris and e-waste. This not only allows these people a space of their own but also reduces the pressure on the Kanjurmarg site.
In view of the various technologies that are being developed, and the methods available to make landfill sites redundant, India needs to up its ante to create a pollution and waste free society, while using the waste that its citizens generate to better the economy.
A case in example is Sweden, which has already converted all its waste into energy and other resources so much so that it needs to borrow (import) waste from its neighbouring countries. It is time to emulate the West for its resourceful concepts rather than its bad habits!