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Enhanced biological tertiary treatment of Municipal Solid Waste (MSW) leachate: a comparative study of conventional technologies with innovative PVA gel technology and its large -scale process optimization

Student Name: Mr Himanshu Chaturvedi
Guide: Dr Priyanka Kaushal
Year of completion: 2020

Abstract:

In India and most of the developing countries, scientific management of Municipal Solid Waste (MSW) is a matter of concern for urban local bodies (ULBs). Unscientific dumping of mixed MSW in dumpsites is still the preferred means of waste disposal for most of the Indian cities.

Ultimate disposal of mixed untreated MSW in dumpsites and unlined landfills signifies an ecological and environmental problem worldwide especially in developing countries. This open dumping of MSW causes problems like odour, vector borne diseases, air and soil pollution including ground and surface water pollution due to generation of leachate.

Leachate is a contaminated, dark brown liquid oozing out from mixed MSW. Leachate generation from accumulated MSW dumpsites and processing facilities affects surrounding environment i.e. air, water and soil in absence of proper treatment prior to its disposal. MSW management in India is still in nascent stages and so is leachate treatment. In present scenario only few conventional processes like aerated lagoons, oxidation ponds and activated sludge process have been used to manage the serious problem of leachate at MSW dumpsites and existing waste processing facilities.

A survey was conducted on the residents living near the Ghazipur dumpsite and East Delhi Waste Processing Company Ltd to assess the impact of generation and presence of leachate around Ghazipur dumpsite. Analysis of the result revealed that there was a direct adverse bearing on the different aspects of human life due to the presence of MSW leachate in the neighbouring area.

Review of literature revealed that conventional treatment processes having physiochemical and biological processes were unable to treat leachate to the requisite discharge level as per the stipulated discharge norms. With the objective to minimize impact of leachate through single or multistage treatment process to achieve desired outlet parameters to ensure environmental and financial sustainability a combination of physiochemical, anaerobic and aerobic biological treatment methods were measured in this study.

Current study purposed to evaluate the novel technological applications Vis a Vis conventional technology for fresh MSW leachate treatment. Selection of experimental technologies had been taken into consideration after analysing different treatment aspects and their implementation on commercial scale.

This study was carried out at a 12 MW Waste-to-Energy Project, owned by East Delhi Waste Processing Company Limited, situated adjacent to Ghazipur municipal waste dumpsite, East of Delhi, India. A pilot plant was setup at the waste processing facility in which physio- chemically, aerobically and anaerobically treated leachate was concurrently subjected to two conventional biological treatment processes i.e. Activated Sludge Process (ASP) and Fixed Film Process (FF) against one novel biological treatment process Polyvinyl Alcohol Gel technology (PVA Gel). These biological treatment processes can also be termed as suspended growth (ASP), attached growth (FF) and attached suspended growth (PVA Gel) processes.

The outcome of these three biological treatments processes were analysed against the experimental parameters like pH, colour, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and oil & grease, wherein the inlet parameters and other physical factors were kept constant. Results obtained from this pilot study were analysed and it was observed that among the experimental treatment processes for treatment of partially treated mixed MSW-leachate the efficiency of PVA Gel process was found better than other two biological treatment processes.

Once the efficiency of PVA Gel technology was established against other two biological treatment processes with the pilot study it was pertinent to optimize the process of PVA gel technology as the tertiary biological treatment process on partially treated MSW leachate for the scale up of this technology. To achieve process optimization of PVA gel technology, partially treated leachate samples were subjected to PVA gel tank.

Parameters like temperature, hydraulic retention time (HRT), BOD, COD and PVA gel loading rate (media loading rate) were analysed and observed to get the process optimization. At a given experiment one parameter was varied within the defined range and other operating parameters were kept unchanged (constant) to get the optimized treatment limit of PVA gel technology for the treatment of MSW leachate. Results established that at BOD level of 600mg/L, COD 1500mg/L, temperature ranges between 30-40°C, media loading at 30-35 Kg/m3/day with HRT of 5hr or more showed maximum efficacy of PVA gel technology.

An analysis of the financial benefits of PVA Gel technology with suspended growth (ASP) and Fixed film (FF attached growth) biological treatment processes for scaling up was carried out. The analysis revealed that PVA Gel Technology was found to have both lower capital and operational expenses over its life cycle.