Wastewater Management
WRF, which currently produces approximately 8m gallons/day of water, began operating in July 2008. It features the largest MBR in North America. Use of membrane bioreactor technology to produce high-
quality effluent for aquifer recharge allows the growing city to earn water credits and therefore extract the equivalent amount of water from the aquifer to augment its supply and meet future needs. With the future addition of several membrane cassettes, the
facility will ultimately produce up to 13m gallons/d of water for aquifer recharge. Black & Veatch provided design and construction-phase
services for the US$135 million facility. The full treatment process includes fine screens, activated sludge with biological nitrogen removal, and UV disinfection as well as membrane filtration. Low-profile structures and effective odour control are designed to make the WRF a good neighbour.
Wastewater treatment MBRs are also finding their way into smaller wastewater treatment processes. Take for example the 1000-acre Laurel Cove Golf & Country Club in middle Tennesee, USA, which is being developed into both a golf course and 800-strong residential community. The decision makers had expressed a strong desire to
incorporate the best available technology to allow for water conservation leading to Bord na Móna being awarded a contract for the design and supply of a PuraM MBR wastewater treatment plant.
A tight schedule was required as local regulation required
that the wastewater plant had to be constructed prior to building the homes. The system installed at Laurel Cove includes 18 flat-plate
PuraM membrane cassettes designed to treat a phase one flow of 250 000 gallons/d and to achieve a final effluent quality of 10mg/l BOD: 20mg/l TSS: 10mg/l TN. The design allows the final effluent to be used as a supply for
irrigation water on the development’s Greg Norman-designed golf course. The PuraM wastewater treatment plant is comprised of
two treatment streams each designed to handle up to 125 000 gallons/d. Each stream has an anoxic/equalisation tank and PuraM MBR tank. Consideration was made in the design to allow for upgrading the system in future phases for flows up to 1 000 000 gallons/d.
Reduced operational input The PuraM MBR was chosen because of its design that is particularly suitable for the decentralised market with an emphasis on reduced operational input, ease of maintenance and less complexity than comparable systems. The flat-plate ultrafiltration membrane treatment technology
is assembled into stainless steel membrane cassettes that consist of an integral dedicated air diffuser assembly that eliminates the need for back-pulsing or frequent chemical cleaning. The system does not require permeate pumps or any site-
installed chemical dosing system while achieving a typical time between recovery cleans of approximately 12 months, significantly better than comparable water reuse systems. n
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