AWWA WQTC60552

The City of Pflugerville, Texas is embarking on a major project to implement a new water supply to meetthe growing needs of its rapidly increasing population. The new water supply will be surface water fromthe Colorado River, which will require complete treatment in accordance with the Rules and Regulationsof the Texas Commission on Environmental Quality (TCEQ). Low-pressure membranes were chosenover other treatment technologies because they provide a positive barrier for particle and pathogenremovals, they remove higher levels of known microbial contaminants, are relatively easy to operate, andthe costs, both construction and annual, are comparable to most conventional treatment technologies.Present design standards for low-pressure membrane technology include an extended coagulant contacttime for the removal of organics and turbidity. If therecommended coagulant contact time prior to the membranes could be reduced to between 15 secondsand 2 minutes, a substantial savings in initial capital as well as operation costs could be realized.Reducing the coagulant contact time could make it possible to provide the necessary contact time in theraw water line between the raw water pump station and the membrane system, thereby saving the costs ofthe coagulant contact/flocculation basin and equipment, as well as the separate membrane feedwaterpumps. For this project, an innovative application of membrane filtration with direct coagulation waspilot tested to determine the feasibility of minimizing coagulant contact time prior to the membranes.At the present time, membrane technology is classified as an alternative treatment technology under thefederal Surface Water Treatment Rule (SWTR). As a result, the TCEQ requires membrane filtrationsystems to provide pilot test data demonstrating that the system will produce water meeting both therequirements of the drinking water standards governing water quality and the reporting requirements forpublic water systems.Based on this requirement, the City of Pflugerville contracted with Pall Water Processing, Ionics, USFilter (later disqualified), and Zenon Environmental to provide complete membrane pilot systems. ThePall and Zenon pilots were skid-mounted units while the Ionics system was a trailer unit. The pilot unitsincluded all pumps, tanks, compressors and other ancillary systems required for full operation during thestudy. Each pilot unit included instrumentation necessary to record important operating parameters, suchas flow rate, temperature, turbidity, particle counts, and system pressures. The same membrane andprocess conditions proposed for the full-scale plant were used in the pilot plants. The membranesmodules tested during the pilot study were identical to and contain fibers of the same length as those thatwill be used in the full-scale plant. The membrane modules supplied with the pilot units were previouslyunused and were not replaced during the test program. Includes tables.

Product Details

Edition:

Vol. - No.

Published:

11/15/2004

Number of Pages:

5

File Size:

1 file , 340 KB