Abstract:
Urban waste management is one of the most complex environmental problems in Sri Lanka.Large quantities of wastes are generated day by day and there decomposition rate is low under anaerobic conditions. Landfill bioreactor is the most suitable system for waste degradation.
The bioreactor landfills with the use of leachate recirculation as a method o f leachate
management is the modem approach for landfill design and operation. Most leachate
recirculation operations performed to date have been conducted on traditionally designed landfills. In future, successful leachate recirculation system will be engineered as part of an integrated bioreactor landfill design. Thus, the design and operation of modem landfills involves many sciences and engineering disciplines, including the biology and chemistry of waste decomposition and leachate production, as well as the hydraulic, geotechnical, and materials engineering required for the design of liners, pipes and pumps.
To successfully operate the bioreactor landfills, it is necessary to control and monitor
biological, chemical and hydrologic processes occurring within the landfill body. It is difficult to control the existing landfill bioreactors and it was found in an earlier study that leachate recirculation system should be maintained under anaerobic conditions. Therefore to obtain the process parameters for controlling the system, the leachate while being under anaerobic conditions, the TS, TSS, VS,VSS, TDS, salinity, conductivity, pH , leachate quantity, BOD and COD were monitored.
As reported in many of the literature, hydrolysis phase is the governing stage o f the reactions to follow. It seems that this phase is prolonged at very low levels of microbial activity leading to large variations between BOD and COD values. Although VS and other parameters are fluctuating, there is an overall increase in the leachate strength. However, the BOD as expected seems to go through carbonaceous and nitrogenous phases, where the first phase had reached a peak at seven days. Also it could be concluded that acicogenesis has been delayed due to the evolution of acid forming gases, namely hydrogen. Thus amendments of the nutrients are essential to promote firstly acidogensis, followed by acedogenesis and finally methenogenesis.
The delays in biochemical transformation may be due also to the type of the waste in this particular "experiment because the quantity o f paper was very high. Further analysis of the results is required to substantiate the conclusions and recommendations made in this study.
