CAPACITIES AND LIMITS OF 3 DIFFERENT TECHNOLOGIES FOR THE BIOLOGICAL TREATMENT OF LEACHATE FROM SOLID-WASTE LANDFILL SITES

Leachate from a municipal waste landfill site was treated using an act ivated sludge bioreactor, a fluidized bed biofilm reactor and a packed -bed column reactor (trickling filter). The leachate contained high or ganic matter (2.0-2.6 g/l of COD), high ammonium (300-700 mg/l) and su lphide (200-800 mg/l) concentrations, as well as low metal concentrati ons. The continuously operating reactors were employed to study the ef fects of TOC loading on the removal of TOC as well as on the nitrifica tion and denitrification processes. Among the three biological treatme nt technologies investigated, the fluidized bed biofilm reactor was be st with respect to removing ammonia and TOC. More than 90% of TOC and 99% of ammonia were removed when TOC loading was less than 0.5 kg/m(3) x d. At a TOC loading of 4 kg/m(3) x d, the removal of TOC and ammoni a was 80% and 99%, respectively. In contrast, the treatment of leachat e with the packed-bed reactor was successful in TOC removing only at T OC loadings less than 0.3 kg/m(3) x d (TOC elimination decreased from 86% at 0.06 kg/m(3) x d to 60% at 0.3 kg/m(3) x d). However, the react or was active in nitrification even at a higher TOC loading (more than a 98% ammonia elimination at a TOC loading of 0.5 kg/m(3) d). Leachat e was processed in the activated sludge reactor when TOC loading was l ess than 0.5 kg/m(3) x d (with a removal of TOC and ammonia up to 83% and 99%, respectively). The activated sludge reactor was also effectiv e in TOC removal at a higher TOC loading (e.g. a 74% TOC removal at a TOC loading of 1 kg/m(3) x d), hut for ammonia elimination, the activi ty continuously decreased (less than 60% ammonia removal at a TOC load ing of 1 kg/m(3) x d). Overloading in the activated sludge system was indicated by a high concentration of ammonia and nitrite in the efflue nt. In the packed bed reactor, overloading was characterized by a prog ressively incomplete TOC removal. No significant overloading was found in the fluidized bed reactor up to a TOC loading of 4 kg/m(3) x d.