Microbiology Procedure

Index >> Waste Water Microbiology >> Composting Compost

Composting Compost

	Composting - Compost - Here the organic part of waste is biodegraded by composting. In this process, the waste is degraded by aerobic, mesophilic and thermophilic microbes. Inorganic fraction is separated either at source or by using magnetic separators. Organic fraction is ground up, mixed with sewage sludge and/or bulking agents (shredded news paper, wood chips) and then composted. This balances C : N balance. Microbial composting converts the waste into a stable, sanitary, humus-like product. The various composting methods are used. These include the following:
1. Window method. Solid waste is arranged in long rows and covered to allow decomposition. Material is turned over repeatedly. 2. Aerated pile method. Here composting rates can be enhanced. Waste is arranged in piles and forced aeration is used to supply extra-02' Perforated pipes are buried inside the compost .pile and the air is then pumped. 3. Continuous-feed composting. It uses a reactor that permits control of the environmental parameters. Reactor is like an industrial fermentor. Here composting is complete in 2-4 days. But this method is expensive.
In compost of domestic garbage and sludge, several microbial species that come from soil, water and human fecal matter are present. High moisture content of the compost favours the growth of bacteria than fungi, Mesophiles are the first to appear and as the temperature rises thermophiles begin to grow. Thermophiles that are dominant in compost are bacteria like Bacillus stearothermophilus, Thermomonospora spp, Thermoactinomyces spp and Clostridium thermocellum, and the fungi, such as Geotrichum candidum, Aspergillus fumigatus, Mucor pusillus, Chaetomium thermophile, Thermoascus auranticus and Torula thermophila.
The reactor is maintained at thermophilic temperatures. Maximum composting occurs at 50-600C, moisture should be 50-600% water content, the C : N ratio must not exceed 40 : 1, the lower nitrogen will not allow the growth of enough microbial biomass.

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