Treatment of Landfill Leachate using Sequencing Batch Reactor

Abstract

In Sri Lanka municipal solid waste is generally disposed in poorly managed open dumps due to lack of liner systems and leachate collection systems. Rain water percolates through the waste layers to produce leachate which drains into ground water and finally to nearby water bodies, which cause degrading the quality of water. Leachate thus has become a major environmental concern in municipal waste management and treatment of leachate is a major challenge for the existing and proposed landfill sites. The present study was conducted to assess the feasibility of the usage of the Sequencing Batch Reactor (SBR) in the treatment of the landfill leachate up to the proposed levels in the draft report of “Proposed Sri Lankan standards for landfill leachate to be disposed to the inland waters". Leachate collected from the open dumpsite at Meethotamulla, Western Province, Sri Lanka was used for leachate characterisation. The SBR was constructed with a 10 L working volume operated in an 18 hour cycle mode and each cycle consists of 15 hrs of aerobic, 2 hrs settle and 0.5 hrs of fill/decant stages. The Dissolved Oxygen (DO) level within the SBR was maintained at 2 mg/l through the aerobic stage. Infeed was diluted with water during the acclimatisation period and a leachate to water ratio of 55:45 was maintained. The removal efficiencies for different parameters were; COD=90.5%, BOD=92.6%, TS=92.1%, conductivity=3.9%, alkalinity=97.4%, hardness=82.2%, Mg=0.5%, Fe=94.2%, Zn=63.4%, Cr=31.69%, Pb=99.6%, sulphate=98.9%, and P=71.4%. In addition, Ni and Cd were completely removed during a single SBR cycle. The dilution of leachate in the dumpsites using municipal wastewater, groundwater or rainwater was identified as the most cost effective dilution methods. The effluent from the SBR proposed to be further treated using a constructed wetland before releasing to surface water.