AWWA JAW65524

This article provides details of one approach for evaluating whether to install low-pressure membranes as part of a water treatment plant (WTP) expansion. Even though the conventional WTP at the Modesto (California) Irrigation District (MID) was exceeding all state and federal water quality requirements, the decision was made to switch to a new filtration technology for the expansion. To verify the membranes' applicability and performance, the MID embarked on an extensive pilot testing program. It also evaluated options for residuals handling and for treating membrane cleaning wastes. Even a well-operated conventional water treatment plant can have good reasons to expand with a newer technology, such as low-pressure membranes. For the MID, the anticipated regional population growth and limited land for future water plant expansions, were significant reasons for expanding its conventional water plant with membranes. The authors have presented information that will be useful for utility managers facing their own treatment plant expansions by providing an example of one approach to evaluating a new technology for a plant expansion. Water utilities can see how MID proceeded with evaluation of low-pressure membranes and how decisions were made. They can also learn about the design considerations for ozone, residuals handling, and disposal of membrane cleaning wastes. Readers will also be interested in the use of a siphon arrangement for drawing water through the membranes, a technique that will help to lower the overall energy use at the expanded facility. Includes 3 references, table, figures.