Lake Erie Continuous MicroFiltration Plant, Ontario, Canada

In July 2002, after evaluating extensive proposals from five membrane system manufacturers, the Municipality of Chatham-Kent Public Utilities Commission in Ontario, Canada awarded USFilter a US$1.7 million contract to provide the first microfiltration plant to treat water from Lake Erie.

SELECTION PROCESS

In May 2000, Chatham-Kent developed a master plan specifically to address future water and wastewater servicing issues in the region. Part of the plan was to focus on two of the region's existing conventional water treatment plants that draw water from Lake Erie. In order to consolidate operations and provide for future water requirements the plants needed to be upgraded or replaced.

During the design of the new plant, five membrane system manufacturers were asked to submit proposals for review. USFilter was selected to supply the membrane technology due to the "best overall life cycle cost while meeting the prerequisite water quality standards".

The bid selection criteria was based on the quality of the water, capital, operating and membrane replacement costs, and experience of the manufacturer.

CONTINUOUS MICROFILTRATION (CMF)

The Memcor CMF system will provide six million gallons of water per day to over 10,000 residents in the Ontario area. The new South Chatham-Kent Water Treatment Plant will service the area of south Chatham-Kent including the communities of Blenhiem and Erie Beach.

Consulting engineers for the Municipality of Chatham-Kent, Totten Sims Hubicki Associates, will provide project management for the scheme.

The CMF technology incorporates a patented air/liquid backwash to remove inorganic or organic contaminants greater than 0.2 microns and prevents them from entering the hollow fibre membranes that form the CMF barrier. The direct-flow (outside-in) filtration through the PVDF oxidant resistant membrane fibres provides an efficient use of membrane area and ensures the removal of contaminants from the raw water source.

The new plant will also include activated carbon for taste and odour control, and chlorine for disinfection. The unit will be commissioned in the spring of 2003.

MICROFILTRATION TREATMENT PROCESS

The Memtek Microfiltration treatment process begins with the transfer of wastewater to one or more reaction tanks followed by controlled addition of pretreatment chemicals to precipitate the contaminants to filterable particles. Reactions are monitored and controlled automatically and continuously. The chemically pretreated wastewater then flows to the concentration tank.

From there, the water is pumped continuously through the 1in tubular membrane filtration modules at a high fluid velocity. At the normal operating pressure (20psi to 40psi), clean water is forced through the pores of the membrane while the contaminated particles remain suspended in the recirculated stream. The turbulence of the recirculated slurry prevents the contaminants from accumulating on the membrane surface, thereby maintaining high and continuous filtration rates. The filtration piping also includes a back-pulse mechanism that reverses the flow of filtrate to maintain higher flow rates and extend the time between cleaning cycles.

The clean water (membrane filtrate) flows by gravity from the membrane modules to a drain, storage tank or the final neutralization tank. Clean, neutralized filtrate is often used for non-critical rinses and applications. The filtrate is ideally suited for further processing by reverse osmosis (RO) for water recycle. The concentration of the wastewater slurry is typically maintained between 2% to 5% solids.

Under normal operating conditions, a portion of the slurry is periodically removed from the system, usually to a filter press that produces a dry (30% 40%) solids cake for disposal. Filtrate from the press is returned to the feed system for reprocessing.

SYSTEM CLEANING

Every E-Series filtration system includes a convenient integral cleaning loop consisting of a pump, two tanks and the necessary piping and valving to permit in-place cleaning of the membrane modules. No disassembly is required and cleaning normally requires less than two hours after 60-100 hours of operation.

US FILTER

United States Filter Corporation, a Vivendi Environnement company, is North America's largest water company providing water and wastewater systems and services to commercial, industrial, municipal and residential customers.

Vivendi Environnement, comprised of Vivendi Water (worldwide water products and services), Onyx (solid waste and industrial services), Dalkia (energy management), Connex (transportation and logistics) and FCC (Spanish company engaged in environmental and construction related industries), is the largest environmental services company in the world with more than 295,000 employees in about 100 countries and annual revenues of more than $25.6 billion.