Environmental Science & Engineering - www.esemag.com - September 2003
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Continuous microfiltration-submerged system ensures high-quality drinking water
The commissioning of a 10.5 million
US gallons-per-day (MGD) continuous
microfiltration-submerged
(CMF-S) system from USFilter
Memcor Products is ensuring a safe drinking
water supply for residents in the West
London, England, area.
Started up in February 2003, the system
is installed at Chertsey Water Treatment
Works (WTW), operated by Three Valleys
Water. CMF-S technology, combined with
downstream ozonation and carbon filtration,
acts as a barrier to bacteria and protozoa,
including cryptosporidium, in the groundwater
wells at the WTW. The system is also
designed to treat water from the River
Thames for short periods, should groundwater
sources be unavailable.
Three Valleys Water awarded the contract
to USFilter’s sister company, Veolia Water
Partnership, and Black & Veatch Contracting Limited, to
design and supply the membrane filtration system following
several months of successful CMF-S system pilot testing.
A pilot study was conducted on two water sources,
Abbeymead well water and the River Thames, which are
susceptible to cryptosporidium contamination. Testing of
the Memcor CMF-S system demonstrated the capability of
the membranes to treat both the groundwater and surface
water sources. The testing on the Abbeymead well water
included oxidization upstream of the CMF-S system to precipitate
iron, allowing the reduction of iron as well as turbidity
and suspended solids. Subsequent pilot testing on
the River Thames, where turbidity ranges between 20 and
50 NTU, with spikes up to 100 NTU, showed that the system
was able to consistently produce product water with
turbidities less than 0.2 NTU, and provide an effective
physical barrier to cryptosporidium.
The CMF-S system at Chertsey WTW consists of six
membrane filtration cells, with each cell containing 192
PVDF membrane modules and “rack inserts” to increase
system recovery and minimize waste disposal. Five of the
six cells will be used to filter the incoming water, with the
sixth cell operating as a backup while one of the other cells
is being backwashed or cleaned. The system’s product
water is sent at a constant flow to downstream ozone contact
tanks, and then to the carbon filters. A programmable
logic controller (PLC) allows the operator to interface easily
with each cell by using the graphical user interface. To
ensure that the microfiltration membrane is providing an
effective barrier between feed water and product water, the
CMF-S system includes a built-in, automated, pressure
decay test, which is easy for the plant operator to monitor.
Three Valleys Water, a Veolia Water company, is the
UK’s largest water-only supply company, serving three million
customers with more than 200 million gallons of highquality
water every day in an area north and west of
London.
For more information, contact www.veoliaenvironnement.com.
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