Leachate Recirculation Aiming At Accelerating Stabilization Of Fresh Refuse In Landfill

Refuse landfill leachate treatment is a world-wide problem due to its high contamination strength and variation of quality. Meanwhile, the refuse in landfill biodegrades slowly and become mineralized after long time stabilization process. Leachate recirculation is an environmentaly-firendly treatment option and the refuse subjected to the recirculation may be biodegraded more effectively so that the refuse can reach stabilized at a short time. Traditional recirculation process would lead to the accumulation of organic acids and ammonia nitrogen, which hinder the refuse degradation.Meanwhile, the aged-refuse-based reactor has been long time used for the cost-effective treatment of landfill leachate, and the COD, BOD and NH3-N can be reduced from 10,000, 5000, and 1800 mg/L to < 300-400 mg/L, 10-20 mg/L and 5-15 mg/L respectively. The effluent looks clear and odorless.In this work, the effluent from the aged-refuse-based reactor was recirculated into the fresh refuse bioreactor, and then the effluent from the fresh refuse bioreactor was introduced into the aged-refuse-based reactor, and so on, until the fresh refuse becomed stabilized and the effluent quality reached COD < 1000 mg/L. The main conclusions are drawn below.(1) For the aged-refuse-based reactor, the effluent quality will be improved when natural ventilation is applied, and the average effluent COD concentrations were 726mg/L and 1076mg/L, ammonia nitrogen 123.7mg/L and 315mg/L, respectively, with and without ventilation.(2) The effluent from the natural ventilation aged-refuse-based reactor was then recirculated into both the anaerobic and natural ventilation bioreactors of fresh refuse so that the volatile fatty acid and ammonia nitrogen accumulations can thus be eliminated and the fresh refuse biodegration can be accelerateed. It was found that the natural ventilation bioreactor recirculation was better than the anaerobic bioreactor recirculation. It was predicted that the COD concentration of leachates would reach 1000 mg/L after 100 days and 2.2 years, respectively.(3) Reaeration recirculation of effluent leachate from two alternate aged-refuse-based bioreactors could greatly improve the blockage of the aged-refuse-based bioreactor and meanwhile the fresh refuse can be stabilized faster when the blockage was overcome. The blockage mechanism was studied based on the relationship between the total organic carbon in the aged refuse and time. Tt was considered that the blocage of the aged-refuse-based bioreactor may be contributed to the adsorption and interception of the organic suspended substances in the leachate.(4) Based on the total amount of degraded pollutant by aged refuse, it was determined that limit load and critical load can be used as the evaluation indexes to prevent the blockage of the aged refuse bioreactor. It was found that the limit load of reaeration recirculation and anaerobic recirculation was 69 and 52.2 gCOD/kg aged refuse, and critical load was 20.9 and 55 gCOD/kg aged refuse, respectively.