Community Benefits from Packaged Membrane System

Located in Northwest Colorado among some of the most famous ski resorts in the U.S., the town of Oak Creek is a quiet and modest-sized community with a population of less than 1,000. Although small, the community benefits from some of the most cutting-edge water treatment technology in the industry with its new 800 gpm membrane filtration plant.

Faced with an out-of-date drinking water system and limited funding and resources, the town of Oak Creek was challenged to find a new drinking water system that could meet its needs. The town’s water treatment system was an obsolete 1940’s conventional water treatment plant, which had been updated sporadically over time, but was ineffective.

“The old plant would not have been able to meet the new State and Federal EPA log removal requirements,” said Jim Photos, director of public works for the town of Oak Creek. “Also, we lost around 50 percent of the treated water due to lack of automatic controls and safeguards.”

Funding and personnel were also critical issues when selecting technology. The town needed a new system that would be cost effective and easy to operate and maintain by one person.

After careful evaluation, the design-build team of Carter & Burgess and Schmueser & Associates recommended a water treatment system that included a submerged membrane package system, which offered a small footprint, low headroom and the flexibility to meet future drinking water regulations.

“With developments in membrane technology reducing the costs associated with membrane filtration systems, small communities like Oak Creek now have the opportunity to benefit from high-tech water treatment systems,” said Seth Leiboh, an applications engineer for USFilter Memcor Products in Sturbridge, MA.

Oak Creek’s membrane filtration system consists of two USFilter Memcor® Axia units. The systems are skid-mounted units containing 48 oxidant-tolerant membrane modules each. All required controls, instrumentation, blowers, compressors and pumps needed for a fully functional system are included. Each skid is 15 feet long and 7.5 feet wide. The height of each unit is 9 feet.

For easier access and maintenance, the membrane module rack is removed from the front of the unit. Because of this removal method, the system requires less height than other systems of its capacity - meeting the building height requirements. With each module weighing less than 15 lbs, the system also reduces the cost of operator maintenance as only one plant operator is required to service the modules and no heavy equipment is required.

The Axia™ system uses Memcor’s submerged membrane filtration system (CMF-S). Axia units consist of one or two cells, which are stainless steel rectangular tanks that house the CMF-S membrane rack assembly. Each Oak Creek unit has two cells, which are manifolded together and run in unison during all sequences of operation. A filtrate and process air manifold are connected to each rack. The Oak Creek systems have 48 membrane modules on the skid - 24 modules per cell.

The submerged membranes use hollow fiber PVDF membranes with outside-to-in filtration to remove particles greater than 0.1 microns from a feed stream. CMF-S systems operate with the filtrate being pulled from the outside to the inside channel of each hollow fiber by a suction pump. Using one unit, the town will be able to produce 200 to 400 gpm. With two units on-line, the town has the flexibility to achieve up to 800 gpm.

For an additional maintenance benefit, the CMF-S system is self-cleaning. A proprietary low-pressure air scour and liquid backwash removes the solids build-up on the membrane surface at regular, operator-adjustable intervals. Periodically, a chemical cleaning procedure (Clean-In-Place) is used to restore membrane performance.

Each serviceable CMF-S module contains thousands of hollow fibers surrounded by a protective plastic screen and sealed with polyurethane pots at both ends. The filter modules can be removed for repair or replacement. And, each membrane rack assembly can be pulled horizontally from the Axia cell, providing ground-level access for service.

“The new water plant is nearly maintenance free, fully automated, extremely easy to operate and produces bottled water quality drinking water,” Photos said.

A three-month pilot study, during the coldest part of the year, confirmed the unit’s flow rates, but also the backwash, clean in place (CIP) and recovery of the overall system. Based on the pilot, the system will be able to achieve longer CIP intervals and higher recoveries than initially anticipated - even when treating water with a temperature less than 1 degree C.

The system went fully operational on October 5, 2004, and is meeting every expectation, Photos said. WW