Full Description

The U.S. Environmental Protection Agency's (USEPA) Guidance Manual requires both directand indirect monitoring of membrane filtration performance by daily integrity testing andcontinuous on-line turbidity testing. Some states have accepted the USEPA guidelines; however,other states require further indirect monitoring and have implemented additional, more stringentrequirements. Many of the regulations and guidelines were promulgated when membranefiltration technology was in its infancy and only limited or pilot testing data were available.The City of Kennewick, Washington completed the retrofit of its Water Filtration Plant (WFP)multi-media filters with a state-of-the-art submerged membrane system. This conversiondoubled the plant's capacity (to 15 million gallons per day [MGD]) within the original footprint.However, during the startup period, the turbidity and particle counts exceeded the WashingtonDepartment of Health threshold limits. The plant's supervisory control and data acquisition(SCADA) system showed that spikes occurred after every backwash and after the daily pressuredecay test (PDT). The output from the on-line instruments confirmed that the spikes occurredapproximately 60 seconds after the backwash cycle and continued for up to 20 minutes.An investigation ensued, and minute air bubbles were observed in the tubing and rotometers thatled to each instrument. It became apparent that entrained/dissolved air was released into themembrane filtrate, migrated to the instruments, and registered as particles, causing false positiveturbidity and particle count readings.The challenge of starting up this submerged membrane system was to meet water demands andmaintain regulatory compliance with instrumentation that is so sensitive that a few tiny airbubbles can trigger an automatic shutdown and indicate that the system is out of regulatorycompliance.Startup procedures required innovative actions to successfully reduce the influence of entrainedair and to demonstrate to the Department of Health that the membrane filtration system was fullyoperational and compliant with state and USEPA guidelines.This paper summarizes the regulatory guidelines of several states in which membrane filtration isused and how these rules can affect full-scale operating and reporting parameters during startup.The regulatory lessons learned at the Kennewick WFP, the largest membrane filtration plant inthe Northwest, are described, as well as lessons learned from other recent membrane plants in theU.S. Includes tables, figures.

Product Details

Edition: Vol. - No. Published: 06/01/2007 Number of Pages: 47File Size: 1 file , 1.5 MB