Factors affecting the fate and behaviour of toxic elements in the activated sludge process

Abstract Laboratory simulations of the activated sludge process have been used to study the removal efficiencies of toxic elements over a range of six sludge ages from 3 to 18 days. Mixed liquor and effluent suspended solids and effluent chemical oxygen demand have been identified as the primary factors controlling the removal of most toxic elements. The effect of sludge age on the solubility of toxic elements in effluent and mixed liquor samples, the relationship between solubility and removal and the accumulation of toxic elements by the biomass have been investigated. The partition of toxic elements appeared to be between the soluble phase and association with particles of greater than 20 μm in diameter for both effluent and mixed liquor samples.

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