Comparative phosphorus removals using modified activated sludge processes
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Date
1977-10-05
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Virginia Tech
Abstract
The operation of three continuous flow units as modified activated sludge models using mean cell residence time as a principal operational parameter has led to the following conclusions:
- Lower mean cell residence times result in higher phosphorus removal efficiencies in biological reactors.
- Higher mean solids residence times result in higher phosphorus removal efficiencies in strictly chemical reactors.
- Calcium-phosphate precipitation can occur in continuous flow reactors in a normal activated sludge pH range (7.5-8.5) given sufficient Ca++ concentrations.
- Calcium-phosphate precipitation can occur in the activated sludge process without hindering COO removal efficiency.
- The phosphorus sludge content only exceeded the one to two percent range in the biochemical and chemical units, where phosphorus precipitation was the predominate phosphorus removal mechanism.
- The anaerobiosis and acid stripping procedure, as used in this investigation, is not effective in enhancing either a biological or chemical unit's ability to remove phosphorus.