AWWA ACE59975

Membrane filtration systems generate several waste streams, including a waste washwater flow that is approximately 10 percent of the total plant treated water production. Provisions for handling the waste streams can have a significant impact on the capital and operating cost characteristics and viability of the treatment plant. Using the design of United Water Idaho's new 6 mgd Columbia Water Treatment Plant (WTP) as a case study, five basic alternatives for waste washwater handling that are typically available to most municipal treatment facilities are presented. This paper discusses the capital cost, power, staffing, maintenance, chemical, space, permitting, reliability, and operational flexibility considerations of each alternative, along with the potential for impacts to water quality or membrane performance. The paper concludes with the selected approach for the Columbia WTP. Includes tables, figures.