Removal of Excess Phosphates

Removal of Excess Phosphates

Removal of Excess Phosphates
Bacterial uptake and storage of P in the form of polyphosphates may be encouraged by modifications in the treatment processes. Enhanced phosphate removal from sludge is associated with polyphosphate storage by Acinetobacter, Moraxella mima group of bacteria. Under anaerobic condition, the microbes incorporate large amounts of fatty acid and store them in the form of Poly Beta Hydroxybutyrate (PHB). When the sewage is re-aerated, the polyphosphate bacteria rapidly oxidise their intracellular PHB and take in the phosphate that is in excess of their growth requirements.

The incorporated phosphate is stored as energy rich polyphosphate in cells thus removing phosphorus from the liquid effluent. All the advanced ASP involves one or more alternate oxic or anoxic sewage storage cycles. Anaerobic or oxidation process includes anaerobic zone with a retention time of 0.5-1 hour and an aerobic tank of retention time of 1-3 hours. During anaerobic phase, inorganic phosphorous is released from the cells as a result of polyphosphate. Energy liberated is used for the uptake of BOD from waste water. During the aerobic process, soluble phosphate is taken up by the bacteria which synthesise polyphosphate using the energy released from BOD oxidation. The AIO process results in the removal of phosphorous and BOD from effluent and produces a rich sludge.

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