Conclusions

Floc formation and associated microbial populations play a key role in the degradation of complex detrital organic matter in the activated sludge process of wastewater treatment. Extracellular enzymes represent an important class of EPS associated with the activated sludge floc particles. The extracellular proteases, lipases, and glucosidases hydrolyze large organic molecules too large to be taken up by bacterial cells to smaller subunits that are readily transported into the cell and metabolized. The floc matrix offers a conditioned environment outside the bacterial cells for these enzymes to carry out their function. Other extracellular enzymes such as PO4ase regenerate the inorganic forms of non-conservative elements such as phosphorus. This represents the initial step in removal of detrital polymeric organic-P from wastewater streams. Since one-third to one-half of the total P in wastewater exists as detrital polymeric organic P, the bacterial populations that produce active PO4ase play a key role in P removal from wastewater in the activated sludge process. Members of the cytophaga-flavobacteria group appear to be particularly important in this regard since they account for 17% to 20% of the total PO4ase-active cells in the system.

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