Effect of sonication on combined treatment of landfill leachate and domestic sewage in SBR reactor

A study was undertaken to examine the biological treatment efficiency of combined waste stream landfill leachate and municipal sewage. The ratio of sewage to leachate was 9:1 by volume. Landfill leachate was pre-treated by sonification. The sonification of the leachate was carried out in static condition using the disintegrator UD-20, the field frequency of 20 kHz and amplitude of 12 μm. For the laboratory experiments a SBR reactor was used, with cylindrical shape and total volume of 5 l. The mixed wastewater was seeded to a mixed liquor suspended solids concentration of 3500 mg/l with activated sludge obtained from the biological wastewater treatment plant. The SBR reactor was operating in 24 hrs time cycle in the following sequential operation phases: aerobic fill, aerobic react, anoxic react, settle, draw and idle. Lab-scale plant was managed by means of different operative strategies in order to find out the optimal one in terms of nitrogen compounds and COD removal. The results indicated that the successful biotreatment of combined leachate and sewage was possible and that treatment efficiency strongly depends on operative strategies. It was also found that, ultrasound pretreatment of raw leachate resulted in improvement of the treatment efficiency. The results show significant improvement of the removal rates of COD and nitrogen compounds in reactor operated with leachate irradiated by ultrasound as compared to biological treatment of non pretreated leachate.