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.