The optimization of anaerobic digestion aims to maximize organic waste stabilization after a short digestion period. This paper presents the optimization performance of the combined anaerobic digestion and sequential staging concept in a thermophilic, solid-state batch system as a treatment technology prior to landfill. The former involves enhanced pre-stage flushing with the addition of microaeration and inoculum in the methane phase. The latter involves leachate cross-recirculation between the mature and fresh waste reactors without conducting a pre-stage operation. The optimized process for combined anaerobic digestion showed that reducing the pre-stage operation with the maximum removal of organics from the waste bed is beneficial. Moreover, the sequential staging concept offers an improved process over the combined anaerobic digestion wherein the specific methane yield of 11.9 and 7.2 L CH4 kg(-1) volatile solids (VS) per day was achieved, respectively. After 28 days of operation, the sequential staging process showed an improved waste stabilization with 86 and 79% mass and volume reduction, respectively. A higher methane yield of 334 L CH4 kg(-1) VS with 86% VS reduction, which is equivalent to 84% process efficiency was obtained.
This study investigated medical waste management (MWM) practices in Bangladesh: its present constraints, the health effect of existing practices, and the weaknesses of the current system. Suggestions for improvement of the MWM situation have also been offered. Those interviewed included hospital staff, waste pickers and local residents. In-depth field observations and a questionnaire survey were conducted in June-July 2000 and March 2001. Laboratory analyses of medical waste were done on different occasions from 1998-2001. Analyses of medical waste showed severe contamination of pathogenic microorganism and respondents suffered from various infectious diseases. The study identified the absence of rigorous laws related to MWM practices. It is a necessity to improve the handling and disposal methods of medical waste in almost all the available medical facilities.
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