Changing characteristics of pollutants in high-rate anaerobic reactor treating landfill leachate

Abstract

Landfilling has been a popular, economical and convenient method of waste disposal of domestic, industrial and hazardous waste. Leachate generated from landfill by contact with precipitation, surface run-off, and groundwater is one of the major environmental hazards. Leachate characteristics are related with the biological phenomena occurring in the landfill as well as with the characteristics of the solid waste. Leachate typically contains organic matter as well as inorganic ions including ammonia and heavy metals in high concentration. Futhermore, leachate characteristics have not been defined clearly. It is, therefore, difficult to treat properly. And it could be detrimental to environment as it contaminates groundwater, soil, and water resources if it is not properly collected, treated, and disposed. It has to be treated by various methods including physicochemical or biological treatment before being released into receiving environment. In this research, the characteristics of pollutants in a UASB reactor treating landfill leachate were studied. Besides, comprehensive studies were conducted to overcome the limitations in anaerobic leachate treatment and to improve its efficiency. Potential problems such as ammonia inhibition, leachate toxicity, precipitate accumulation, and limited use of anaerobic process were also investigated. The UASB reactor could be effective for various industrial wastewaters containing high concentration of ammonia nitrogen. The COD removal rate was about 80% at ammonia concentration up to 6000 mg-N/l. The inhibition threshold value of anaerobic treatment was 490 mg-N/l of free ammonia nitrogen. However, the methane yield decreased with increasing ammonia nitrogen. The ammonia nitrogen concentration I50, causing 50% inhibition of SMA were 2670, 4780, and 5570 mg-N/l, respectively. The kinetic coefficients (l, m, and n) of ammonia inhibition using formate, acetate, and propionate as substrate were 3.28, 1.00 and 0.60, respectively. ...