The removal of ammonia from sanitary landfill leachate using a series of shallow waste stabilization ponds.

This study evaluated the efficiency of a shallow (0.5 m deep) waste stabilization pond series to remove high concentrations of ammonia from sanitary landfill leachate. The pond system was located at EXTRABES, Campina Grande, Paraiba, Northeast Brazil. The pond series was fed with sanitary landfill leachate transported by road tanker to the experimental site from the sanitary landfill of the City of Joao Pessoa, Paraiba. The ammoniacal-N surface loading on the first pond of the series was equivalent to 364 kg ha(-1) d(-1) and the COD surface loading equivalent to 3,690 kg ha(-1) d(-1). The maximum mean ammonia removal efficiency was 99.5% achieved by the third pond in the series which had an effluent concentration of 5.3 mg L(-1) ammoniacal-N for an accumulative HRT of 39.5 days. The removal process was mainly attributed to ammonia volatilization (stripping) from the pond surfaces as a result of high surface pH values and water temperatures of 22-26°C. Shallow pond systems would appear to be a promising technology for stripping ammonia from landfill leachate under tropical conditions.

Performance of constructed wetland systems treating anerobic effluents.

The purpose of this present paper is to verify the performance of three wetland systems operated with effluents from a UASB reactor, with respect nutrient removal (nitrogen and phosphorus), pathogenic organisms and remaining carbonaceous material, monitored over a three-year period. The experiment was carried out and monitored at PROSAB (Programa de Saneamento Básico) in Campina Grande, Paraíba. The removal efficiency of the carbonaceous material expressed in DQO ranged from 70 to 86%, but concerning the total suspended solids, the efficiency ranged from 50 to 71%. The removal efficiency in terms of nitrogen and phosphorus of both vegetated systems was about 65.5 to 86%, respectively, during the first year of operation. Under the operational conditions of the experiment, the removal of phosphorus in a wetland system containing washed sand as the substratum decreased, as its operation period increased. The vegetated wetland has been the most efficient in removing faecal coliforms (roughly 4 log units) as compared to the non-vegetated one (about 3 log units), when both were operated with the same hydraulic load (2.3 cm. per day). Thus, the effluent produced over the three-year period ranged from 800 to 1,800 UFC/100 mL in the analyzed samples.

Post-treatment of anaerobic effluents in constructed wetland systems.

This papers describes the behaviour of wetlands as a post-treatment unit for anaerobically treated sewage for the removal of organic matter, suspended solids, nutrients (nitrogen and phosphorus) and faecal coliforms. Raw sewage was treated in a UASB reactor with a retention time of 5 h and the effluent was used in four units of wetlands with coarse sand as the medium and operated with different hydraulic loads. Three of the units had emerging macrophytes (Juncus sp), whereas the fourth one was operated as a control unit without plants. During the 12 months of operation, the organic material removal efficiency (measured as COD) was in the range of 79 to 85%, whereas suspended solids removal varied from 48 to 71%. Faecal coliform removal was very high (99.99%); phosphorus was also efficiently removed (average efficiency of 90% for the lowest hydraulic load), but nitrogen removal was only partial (45 to 70% for ammonia and 47 to 70% for TKN). The experimental results clearly show the technical feasibility of using wetlands for treatment of municipal sewage after a pre-treatment in the UASB reactor.