Potable Water
A healthy beginning for the Wawa Water Treatment Plant by Brian Sahley and Bruce McMullan
The architectural design makes the facility an attractive addition to Wawa’s downtown core. The simplicity of the process layout makes it a “beautiful facility to work in”.
oil Advisory – most of us recognize this term as an emergency response. For the people of Wawa, it was a way of life for three years while a new water treatment plant (WTP) was designed and constructed. Late in 2006, the elation of the 3,400 people in this small mining heritage town in Northern Ontario could be heard far and wide when the main gate valve was turned and safe, clean, membrane–filtered water entered the municipal system. The journey began in May 2003 with the completion of the Wawa Water System Upgrading Class EA, Environmental Study Report (part of a Schedule C, Class EA). Study conclusions included: • Converting the existing WTP to a low lift pumping station (PS). • Construction of a new WTP. • Installation of a watermain from Wawa to the Michipicoten River Village elevated water tank. Following the study, in September 2003, the Township of Michipicoten retained KMK Consultants Limited to complete the design and construction of the new plant. Based on first principles, KMK conducted a water quality assessment of Wawa Lake and then held a comprehensive process/technology review and workshop with the municipality. This exercise was conducted so that the
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options could be fully explored, forming the basis for an informed decision on the best process solution considering all the various technical and cost merits. Membrane filtration was selected as the preferred alternative based on higher levels of treatment and anticipated future regulations. KMK proceeded to pre-select the preferred membrane vendor and then to conduct confirmatory pilot testing with the pre-selected vendor. In the meantime, the design for a new 6 ML/d plant, including a 3 ML reservoir, was fasttracked and completed in 98 working days. The design included the refurbishment of the previous WTP to a low lift PS, raw watermain, microscreening, pressure membranes, chemicals area, high lift pumps, electrical, laboratory, control room, offices and workshop all in one integrated structure situated in a small, confined site in the downtown core. PALL Corporation was selected as the preferred membrane vendor. Pilot testing of its ARIA AP4 microfiltration membrane system confirmed the necessary requirements for design criteria and performance. The system has a rating of > 4 Cryptosporidium and Giardia log removal. As part of the pilot testing, powdered activated carbon (PAC) was added up to 50 mg/L. Provision for future PAC addition was incorporated into the final
design that is based on three skid mounted units. The Pall ARIA AP4 system uses the proprietary Microza membrane system in unitized modules for ease of maintenance, servicing and efficient treatment of the water. “We have yet to fail an I.T. test which would indicate to me that no broken fibres have occurred (i.e., no visible signs),” says Mark McRae, Water and Sewer Lead Hand. Turbidity used to be an issue for the previous WTP. “We have seen such an improvement in turbidity levels with the membrane filtration process from the previous PS which had no filtration”, says Bill Lamon, Director of Infrastructure Services. The WTP should not have a problem achieving less than 0.1 NTU, 99% of the time. The beauty of this new facility lies within the design - the simplicity of the process, ease of operations and maintenance, and the compact footprint. The simplicity of the process begins with 610 mm diameter intake pipe from Wawa Lake. The old WTP was converted into a low lift pumping station with three new pumps (two duty and one stand-by). These pumps convey the water to the membrane system where it is ‘pushed’ through thousands of tiny tubes with a diameter less than that of a grain of salt, removing harmful microorganisms and parasites. The filtered water is then treated with chlorine for primary disinfection and retained in chlorine contact chambers (CT cells) to provide adequate disinfection contact time. The high lift pumps convey treated water to the municipal distribution system which is a closed distribution system and operates on pressure only. Membrane wastewater is discharged to two wastewater equalization tanks, with
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