Characterization and biological treatment of pre-treated landfill leachate

•The application of anaerobic, aerobic and their combination to landfill leachate treatment has been investigated.•The use of ammonia stripping step prior to biological treatment increased the efficiency of the overall treatment process.•Landfill leachate has to be diluted by 50% using sewage to be amenable to biological treatment.

Characterization and biological treatment of leachate generated by Borg El-Arab landfill has been carried out. Intensive monitoring of the leachate indicated that it is moderately biodegradable. The BOD/COD ratio is in the range of 0.33–0.45. The ratio of COD:N:P was 100:39:0.3 indicating high nitrogen and low PO4-P content. Three experimental sets of treatment schemes were conducted: aerobic, anaerobic and combined anaerobic/aerobic. To assess the impact of the applied organic load on the performance of the treatment processes, the leachate was diluted using sewage. Three different leachate concentrations were used, 5.9%, 25% and 50%. These correspond to average COD values of 1166, 4207 and 7830 mgO2/l, respectively. Each treatment scheme was fed with the three dilutions. The same sets of experiments were repeated after pre-treatment using air stripping to remove ammonia nitrogen. The results obtained indicated that ammonia stripping for 6 h after adjusting the pH of the leachate (1:1) at 10, coupled by aerobic treatment via activated sludge for 24 h achieved the best results. Ammonia removal was more than 90%. Corresponding COD and BOD removal values reached 64.4 and 67.2%, respectively.