NEW PRIMARY SCUM HANDLING SYSTEM FOR THE CITY OF DETROIT'S WWTP - AN INNOVATIVE APPROACH

The Detroit Water and Sewerage Department's (DWSD's) Wastewater Treatment Plant (WWTP) primary treatment system, one of the largest in the world, will have a peak capacity of 1,800 mgd in 2004. Primary treatment capacity is evenly divided between circular and rectangular primary clarifiers. Scum removal and handling at the circular primary clarifiers has caused significant operations and maintenance challenges since the clarifiers were constructed over 25 years ago. An on-going project (PC-740) is constructing two, new circular clarifiers with a redesigned scum removal and handling system. Because of the scum removal challenges with the existing clarifiers, this project is also retrofitting the scum removal and handling systems for the four existing circular clarifiers, which are similar in size and capacity. The total cost of the project is about 90 million, of which about 20 million is for the scum removal improvements. This paper describes the proven solutions for significantly improving the scum removal and handling system for the circular clarifiers using an innovative approach of a fullscale pilot test of the system on one clarifier and implementing the improvements on subsequent clarifiers.