EVALUATING SECONDARY CLARIFIER COLLECTOR MECHANISMS

Controversy continues among wastewater treatment facilities owners and operators, consulting engineers, and process equipment manufacturers and their representatives as to the advantages and disadvantages of alternative sludge collection mechanisms for secondary clarifiers in the activated sludge process. This paper summarizes the four alternative collector mechanisms available while presenting an evaluation of the advantages and disadvantages of each mechanism. These evaluations incorporate the results of several recent engineering studies.The paper concludes that, from a process perspective, the suction plenum or Tow-Bro mechanism offers significant advantages over all presently available mechanisms and recommends that new secondary clarifiers or retrofitted existing secondary clarifiers utilize this design.This paper concludes by suggesting that additional improvements in the design of secondary clarifiers may be achieved in the future through the use of mathematical models of the secondary clarifier coupled to existing models of the activated sludge process and the flow regimes in which these systems operate.