AWWA ACE95104

This paper addresses the potential impacts on finished water quality of various alternatives for handling the liquid and solid residual streams in a conventional water treatment plant (WTP) that uses surface water as its source. The Cleveland Division of Water (CDW) is in the process of upgrading and expanding its Crown Waterworks facilities; one of the CDW's four WTPs. The existing facilities are being upgraded since the original Crown WTP went online nearly 40 years ago. The present facility has a rated capacity of 50 million gallons per day (MGD), and the expansion portion of this project is increasing the rated capacity to approximately 125 MGD; mostly by converting existing conventional, unit treatment processes (e.g., clarification and filtration) to high-rate ones. An overview of the CDW's system is provided to put the waste stream recycling alternatives presented in this paper into proper perspective. The three Phase approach to upgrading/expanding the Crown WTP is discussed: pilot-scale demonstration study; rehabilitation (upgrade) design; and expansion design. The benefits of this three Phase approach are enumerated, particularly in terms of how the Phase I pilot-scale demonstration study was used to generate the necessary data for: justifying the proposed high-rate clarification and filtration processes to the regulatory agency (i.e., the Ohio EPA); developing the appropriate design concepts for these unit treatment processes to be used in Phase III; and making sure sufficient flexibility was built into the design so applicable current and anticipated drinking water regulations could be consistently met. Finally, the residual solids management (RSM) alternatives considered for this project, as well as the methods/reasons employed to select the recommended alternative, are presented.