ANAEROBIC AND SEQUENTIAL ANAEROBIC-AEROBIC TREATMENTS OF MUNICIPAL LANDFILL LEACHATE AT LOW-TEMPERATURES

Anaerobic treatment of municipal landfill leachate (COD 1-4 g l(-1), N H4-N c. 0.16 g l(-1)) was studied at 11 and 24 degrees C by using labo ratory-scale UASB and hybrid reactors. Aerobic post-treatment of the a naerobically treated leachate was also studied at 24 degrees C using a n activated-sludge process. In the 11 degrees C reactors, a COD remova l of up to 60-65% was obtained with 1.5-2 day HRT and 0.7-1.5 kg COD m (-3) day(-1) organic loading rates. At 24 degrees C, a COD removal of up to 75% was achieved with a 10 h HRT. The highest organic loading ra te applied was 10 kg COD m(-3) day(-1) at 24 degrees C. Inorganic mate rial accumulated in the reactor sludges at both temperatures. However, the specific methanogenic activity of the 24 degrees C reactor sludge did not decrease during the 282 days of operation. After 196 days of operation, the specific methanogenic activity of the 11 degrees C reac tor sludge was one-third of that of the 24 degrees C sludge. The aerob ic post-treatment removed 45-75% of the COD left after the anaerobic t reatment removed 45-75% of the CoD left after the anaerobic treatment and produced effluent with a BOD7 of less than 22 mg l(-1) and a COD o f less than 380 mg l(-1). The COD removal in the sequential process wa s 80-90%. An ammonium removal of up to 80% and a total nitrogen remova l of 40% were achievable in the aerobic stage. The results showed that the anaerobic treatment of medium-strength leachate was feasible even at 11 degrees C. The sequential process produced effluent quality clo se to the requirements set for municipal wastewater treatment plants. Copyright (C) 1996 Elsevier Science Ltd.