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Introduction
The Olivenhain Municipal Water District's (OMWD) new treatment facility represents one of the largest ultrafiltration plants in the world. The plant was designed for an initial flow of 25 MGD, expandable to 30 MGD (with additional membranes and equipment) and consists of eight independent process trains, each with the capacity of approximately 3.125 MGD. The facility also includes a three train second stage membrane system that treats the reject flow from the first stage, resulting in up to 99% recovery.
David McCollom, General Manager of Olivenhain called attention to the specific issues surrounding the Olivenhain project: "We needed a treatment plant that we could build initially to handle a specified treatment capacity and then could easily be expanded. We also had a confined space in a valley where we were going to build and there were several environmental concerns."
With the advent of various new approaches to water treatment over the years, Olivenhain's Board of Directors and its consulting engineer, Boyle Engineering, resurrected the old practice of putting each proposed treatment system to the test…head to head. "We needed to make this a proposal process rather than a bidding process", commented Doug Gillingham, Project Manager, Boyle Engineering. "Each company had their own proprietary technology and we felt it was extremely important that we compare "apples to apples".
By 1999, the OMWD selected ZENON to supply a ZeeWeed® based membrane filtration system. "Although all competing technologies were impressive, ZENON stood out because of its ease of operation and maintenance, its convenient adaptability and its durability," concluded Doug Gillingham, Boyle Engineering.
Process Overview
Reservoir water is pre-screened with a fine screen, chlorinated for control of biological growth and directed to the ZeeWeed® membrane tanks, with no further pretreatment. Filtration is achieved by drawing water to the inside of the membrane fiber under a low-pressure suction of –1 to –8 psi, created by a permeate pump. The treated water then flows to the main permeate collection pipes.
The membrane surface is kept clean through aeration and membrane back-pulsing. Diffused air is introduced from the bottom of the membrane module and travels along the surface of the membrane, removing any solids that may have settled. At preset time intervals, the membranes are back-pulsed. This is accomplished by briefly reversing the flow of permeate through the membrane to remove any particles that may have obstructed the pores during membrane operation.
A programmable logic controller combined with a plant SCADA system, monitors the entire system and makes adjustments to pump speeds and valves to ensure the facility is operating at optimal performance.
A unique feature of the plant is the inclusion of energy recovery turbines directly coupled to centrifugal blowers and induction generators. These turbines take advantage of the 24,000 acre-foot reservoir located approximately 150 ft. above the plant, thereby allowing the facility to be operated with a significantly reduced demand on external electrical power by making use of the static head to generate power via the induction generators.
“When you couple the technological capabilities of their system with the experience, creativity and integrity of their people, ZENON is making quite a name for themselves”, commented Kimberly Thorner, Esq. Project Administrator in the OMWD project. "ZENON's proposal to our District was cost competitive, solid throughout and very creative. We stand to save millions of dollars when compared to our initial design concepts. We were impressed by both the high quality of their product and the skills and expertise of their staff."
About ZENON Enviromental Inc.
ZENON is a global leader in the development and manufacturing of membrane technologies and systems for water treatment, wastewater treatment and water reuse. With thousands of installations worldwide, ZENON is providing cost-effective and reliable solutions to challenges faced by municipalities, industry and government agencies.
Web site: http://www.zenonenv.com/
Source: ZENON Environmental Inc.
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