Biodegradation and Recycling of Urban Solid Waste
ABSTRACT Problem statement: Rapid urbanization and population growth are largely responsible for very high increasing rate of solid waste in the urban areas, its proper management and recycling is major problems of Municipal Corporation. The proposed study attempted to proper management, physicochemical analysis of Urban Solid Waste (USW) and its conversion to enriched compost by ecofriendly process. Approach: For this study, we used turned windrows method for composting of USW, microbial inoculums added uniformly and temperature, pH, moisture maintained throughout the composting process. The chemical composition of compost obtained at the end of the composting process compare to the United State Environmental Protection Agency (USEPA) standards. Results: A study in Jabalpur had shown the 47% of Urban Solid Waste (USW) were degradable and 53% non-degradable. The initial compositions of urban waste were indicates an organic carbon status of 38% with the C: N ratio of 950. The additives used in solid urban waste composting such as cow dung and green manure recorded organic carbon content of 25.60 and 34.60 and C:N ratio of 30.11 and 11.23. Conclusion: The results of the study clearly indicate that the recycling of solid urban waste can transform garbage or municipal solid waste to enriched composts. This is practical significance if adopted by urban farmers as a result of soil health and in turn the productivity of soil can be maintained for further agriculture.
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ABSTRACT: Modeling composting processes is the prerequisite to realize the process control of composting. In this paper, a simulation model for domestic solid waste composting processes was developed based on microbial process kinetics, mass conservation equation, energy conservation equation and water balance. Differential equations describing microbial, substrate, oxygen concentrations, moisture content and temperature profiles were derived. Considering that several factors (temperature, oxygen, moisture and FAS) in the process interacted to composting processes, microbial biomass growth kinetics was described. In order to verify the model, a series of aerobic composting experiments on domestic solid wastes were conducted. Temperature, moisture, microbial biomass growth, oxygen consumption rate and the concentrations of organic components were monitored in the composting processes and also simulated with the developed model. The simulation results were well consistent with the experimental results. It also could be seen from the model that the efficiency of composting processes could be raised and aeration requirements could be reduced by controlling the oxygen concentration in the exhaust air within a proper range. When the range is 8% to 12%, the aeration requirements reduced 79.61%. This result was verified by the composting experiment. When initial moisture content was higher than 66% or lower than 33%, it would significantly reduce the rate of substrate degradation. It indicated the effect of initial moisture content on the composting processes was significant. A simple sensitivity analysis demonstrated that two key parameters in composting modeling to determine were maximum specific growth rate (max µ) and yield coefficient (Y Y/S). Therefore, the composting processes could be optimized by the application of the developed simulation model. [The Journal of American Science. 2005;1(1):34-45].The Journal of American Science. 01/2005; 1.
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ABSTRACT: This study investigates the prevailing physico-chemical conditions and microbial community; mesophilic bacteria, yeasts and filamentous fungi, bacterial spores, Salmonella and Shigella as well as faecal indicator bacteria: total coliforms, faecal coliforms and faecal Streptococci, present in a compost of municipal solid waste. Investigations were conducted in a semi-industrial pilot plant using a moderate aeration during the composting process. Our results showed that: (i) auto-sterilization induced by relatively high temperatures (60-55 degrees C) caused a significant change in bacterial communities. For instance, Escherichia coli and faecal Streptococci populations decreased, respectively, from 2 x 10(7) to 3.1 x 10(3) and 10(7) to 1.5 x 10(3) cells/g waste dry weight (WDW); yeasts and filamentous fungi decreased from 4.5 x 10(6) to 2.6 x 10(3) cells/g WDW and mesophilic bacteria were reduced from 5.8 x 10(9) to 1.8 x 10(7) bacteria/g WDW. On the other hand, the number of bacterial spores increased at the beginning of the composting process, but after the third week their number decreased notably; (ii) Salmonella disappeared completely from compost by the 25th day as soon as the temperature reached 60 degrees C; and (iii) the bacterial population increased gradually during the cooling phase. While Staphylococci seemed to be the dominant bacteria during the mesophilic phase and at the beginning of the thermophilic phase, bacilli predominated during the remainder of the composting cycle. The appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse. Compost sonication for about 3 min induced the inactivation of delicate bacteria, in particular gram-negatives. By contrast, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in the compost.Bioresource Technology 01/2002; 80(3):217-25. · 4.75 Impact Factor
Article: Soils and soil fertility