Table 172

Hypotheses Explaining the Causes of Activated Sludge Deflocculation

Factors associated with sludge deflocculation

Extracellular polymeric substances (EPS)

Microbial community shifts

Bacterial physiological responses

Microbial metabolism

Abiotic processes

Hypothetical mechanisms

Physiological inhibition of EPS production79,83 Production of EPS degrading enzymes101 Depletion of EPS and PHB due to substrate deficiency19; EPS degradation under anaerobic storage with microbial reduction of ferric iron and sulfate98

Death of floc-forming bacteria with a narrow range of temperature tolerance; death of aerobic floc-forming bacteria due to anaerobic conditions; outbreak of non-flocculating populations due to phenolic step loadings causing effluent turbidity102 Bacterial and protozoan-metazoan lysis, which deactivates bacterial flocculating properties and changes physico-chemical interactions among flocs

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