The Lake Dunlap Water Treatment Plant is owned by the Canyon Regional Water Authority (CRWA) and is located in New Braunfels, TX.
Click here to enlarge imageAdditionally, PMPW membranes from KMS are credited with 4-log (99.99%) removal of Giardia, Cryptosporidium and viruses by the California Department of Health Services.
Capacity Expansion
By mid-2003, Canyon Regional Water Authority needed to increase capacity to meet customer growth that was outpacing earlier projections. CRWA decided to install the PMPW-10 cartridge, a newly available, 10-inch diameter UF hollow fiber cartridge from KMS containing 60% more membrane area and capable of filtering 60% more product water than its 8-inch predecessor.
During the summer of 2005, six PMPW-10 filtration units were commissioned, producing 14.4 mgd at the New Braunfels plant. The original two PMPW-8 units were moved to the San Marcos plant to expand the previously installed PMPW-8 system.
“Our systems are highly automated. They maintain low transmembrane pressure, with a once-a-month cleaning routine,” Davenport said.
The monthly Clean-In-Place (CIP) protocol consists of recirculating softened potable water containing 200 ppm of chlorine through the membranes at 95 to 110ºF at a pH adjusted to 12 with sodium hydroxide. Occasionally a citric acid solution (pH 3) is used.
The use of chlorine dioxide to control algae has been an effective pretreatment step for the New Braunfels system. Approximately 1 ppm of chlorine dioxide is injected into the raw water line year-round, with a typical residual of 0 to 0.3 ppm going into the membrane system.
High automation and low maintenance are not only important at larger facilities, but smaller ones as well, as exemplified at the Martindale Water Supply Corp., a 0.5 mgd facility located a dozen miles southeast of the San Marcos plant. A 13-cartridge PMPW-8 system, brought online in February 2001, filters well water for 2,500 Martindale area residents. This facility also must comply with the Surface Water Treatment Rule, because it uses ground water under the influence of surface water.
“I am the only employee at this facility, besides the office manager, and therefore ease-of-maintenance is critically important,” said Steven Fonville, general manager of the Martindale Water Supply Corp. “We barely have to clean the membrane system. However, we do perform a cleaning every six months as a formality, so we don’t forget how the process works.”
Successful operation of membrane ultrafiltration plants at the New Braunfels, San Marcos and Martindale plants has spurred wide interest in the technology in south central Texas.
“We were one of the first plants, and now there are 15 to 20 similar plants in Texas, in construction or in the process of coming online,” Fonville said. WW