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Journal of Biological Sciences

Year: 2008 | Volume: 8 | Issue: 2 | Page No.: 368-373
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Authors

L. Mpenyana

M.A.A. Coetzee

S. Schwarzer

Keywords

Research Article

Removal of Ammonia from Landfill Leachate in a Two-Stage Biofiltration Process

L. Mpenyana, M.A.A. Coetzee and S. Schwarzer
The efficiency of nitrification and denitrification in a two-stage biological filter in the removal of ammonia from sanitary landfill leachate, using plastic media, was investigated. A pilot-scale biological filter constituted of leachate from Weltevreden sanitary landfill was built. During the first 25 weeks of the investigation no external carbon source was added. To facilitate denitrification methanol was added to the pilot-scale. The first 9 weeks of the study was characterised by the raw leachate that had an average pH value of 8.89±0.13, an ammonia-nitrogen concentration of 450±20 mg N L-1 and a COD concentration of 1600±116 mg O2 L-1. The change in raw leachate characteristics resulted in the decrease of pH and alkalinity which necessitated the addition of soda-ash (Na2CO3) to achieve complete nitrification in the first stage of the pilot-scale. A decrease in ammonia-nitrogen was noted from 200±10 to 2±2 mg N L-1 and a 99% ammonia removal was therefore recorded after Stage 1. In Stage 2, denitrification took place after the addition of the methanol at a methanol:nitrate ratio of 1.23:1. The nitrite and nitrate were 0.20±0.02 and 13.67±0.58 mg N L-1, respectively, at the end of the experiment which was acceptable according to the general authorisation from the Department of Water Affairs and Forestry (DWAF). The COD removal was very poor since only 36% was removed at end of the experimental period; which meant that 64% was non-biodegradable. Ammonia-nitrogen from landfill leachate can be removed by a two-stage biofiltration process.
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