Microbial Reactions and Quality of Substrate

An example of an aerobic, heterotrophic microbial reaction is the degradation of glucose (cf. Examples 2.2 and 2.3)  

Anoxic conditions require the absence of DO and the presence of nitrates. Such conditions are typically only found when artificially implemented. The aerobic and anoxic pathways of organic matter degradation are identical. The addition of nitrate to wastewater is widely used as a control measure to avoid anaerobic conditions in sewers (Section 6.2.7). 

As a result, the partial breakdown of the organic matter by fermentation yields organic products with a low molecular weight, e.g., VFAs, along with C02. Compared with the aerobic respiration, the fermentation is inefficient however, these fermentation products can to some extent, and in addition to fermentable substrate, be used by the sulfate-reducing bacteria that make use of sulfate as the terminal electron acceptor (Nielsen and Hvitved-Jacobsen, 1988). In the absence of sulfate, the methanogenic bacteria utilize the low molecular 

The anaerobic decomposition of organic matter by fermentation, methanogenesis (methane formation) and sulfate respiration is exemplified in Table 3.2. 

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