Effects of phosphorus addition on treatment efficiency of an anaerobic filter treating landfill leachate

Sanitary landfill leachate is a source of environmental concern due to its high organic strength and chemical diversity. The widespread use of sanitary landfills has resulted in regulatory authorities requiring municipalities to give serious consideration to the treatment and safe disposal of this wastewater. A number of lab-scale and pilot scale studies have indicated that the anaerobic filter .is highly competitive with other forms of biological treatment and has distinct economic advantages. While there have been a number of studies based on a general overall approach to leachate treatment by the anaerobic filter, limited' information is available on the role played by essential nutrients (phosphorus and nitrogen) in the biological treatment process. Laboratory studies were conducted at room temperature (22°C) to study the effect of nutrient addition (specifically, phosphorus, the deficient constituent of most leachates) on treatment efficiency of landfill leachate by the upflow anaerobic filter. Two anaerobic filters (0.975 metres x 0.15 metres diameter) were constructed using plexiglass pipes and packed with strips of corrugated fibre-glass sheets in four layers to form the filter bed. Leachate collected from a nearby landfill was applied at moderate organic loadings (2.0-4.2 kg COD/m³.day) to the two units maintaining a HRT of 0.987 days. During runs 2 and 4, leachate collected from the Premier landfill had a very low organic strength, necessitating the addition of acetic acid to raise that strength to around 2000 mg/l COD. When phosphorus addition was made at the 10 mg/l level to this feed, no favourable effect on COD removal was observed, possibly because the feed was VFA based and not inclusive of complex organics. During run 3, the strength of the leachate increased to around 4000 mg/l, with a relatively lower proportion of the COD present as VFA (around 1600 mg/l as acetic acid). When phosphorus addition was made to this feed at a 40 mg/l level, COD removal capacity of the anaerobic filter improved significantly, indicating that phosphorus may be added to an organically diverse waste with distinct advantages.Applied Science, Faculty ofCivil Engineering, Department ofGraduat