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Steps in the Water Treatment Process |
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Intake: |
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Located at the northeastern edge of
Lake Erie, in a region known as the Emerald Channel. It serves as a
conduit, directing Lake Erie water to an onshore Screen House. Chemical
treatment can begin at the Intake. Chlorine gas is routinely introduced
at the Intake when the temperature of Lake Erie reaches, and exceeds, 50
degrees Fahrenheit, for zebra mussel control.
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Raw Water
Conduit:
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Lake water is transported by
gravity, to the treatment process through the raw water conduit.
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Screen House: |
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Located onshore within the Colonel
Ward Pumping Station Complex. The Screen House consists of 2 banks of
traveling screens, which mechanically filter large debris from the raw
water entering the treatment process. Occasionally a cationic polymer
may be added after mechanical filtering to begin the coagulation
process, when floc resistant algae enter the lake. |
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Chlorine Gas and Fluoride Feeds: |
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Chlorine gas is added to the raw water conduit to kill
pathogens. A fluoride solution is also added to promote dental health. |
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Thickener Decant Stream: |
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filter backwash water enters the raw water conduit vault through the
Thickener's decant stream. This allows the processed backwash to be
exposed to the entire water treatment process. |
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Coagulant Feed: |
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important part of the treatment process is the coagulant feed. This
causes fine particles in water to clump together allowing the removal of
viruses and parasites, that are too small to filter without
agglomeration. |
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Low Lift Pumps: |
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low lift pumps serve a dual purpose. They serve to mix the chemical feed
introduced to the raw water conduit, and they transport the water toward
the surface to the Treated Water Conduit. |
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Treated Water Conduit: |
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This conduit transports the chemically treated water
through the flocculation stage. |
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Rapid Mix: |
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is a mechanical mixer within the treated water conduit that allows for
additional chemical feeds to be introduced to the water treatment
process prior to sedimentation. |
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Polymer Feed Line: |
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This is a static feed line within the treated water conduit, that allows
for an additional polymer coagulant feed to be introduced to the water
treatment process prior to sedimentation. |
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Flocculators: |
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Water, from the treated water conduit
is directed underground to a series of large, slow-moving mechanical
paddles which promote the formation of floc. The previously
introduced coagulant imparts a charge to particles in the water. The
slow mixing induced by the flocculators cause these particles to clump
together. This helps to improve the settleabilty or filterability of
debris in water. |
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Sedimentation Basin: |
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Floc-laden water is introduced to a
large baffled basin. The baffling serves to limit the velocity of the
water and further encourage particle clumping. The heavier dense settle
by gravity to the bottom of the basin, where they accumulate as sludge.
The lighter clumps will float or suspend within the basin's water,
destined to be removed through filtration. |
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Settled Water Conduit: |
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Treated water leaves the sedimentation
basin via the settled water conduit en route to the rapid sand filter
banks.. This water contains floc that is too light to settle out in the
sedimentation basin. |
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Chlorine Gas to Filters Feed: |
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Within the settled water conduit is
another chlorine gas feed. This disinfectant feed allows the plant to
increase the chlorine residual of the treated water prior to entering
the filter beds and clear well storage. |
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Coagulant to Filters Feed: |
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When necessary a coagulant is added to
the settled water conduit to increase the filterability of the treated
water prior to filtration. |
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Rapid Sand Filters: |
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Water is directed from the settled water conduit to the
rapid sand filters, where lighter floc, created in the sedimentation
basin, is removed from the treated water. The rapid sand filters use
anthracite, derived from coal, as its' filter media. Filtration occurs
through adsorption on the anthracite's surface area. The filtered water,
now cleared of floc and debris, is directed to an underground clear
well. |
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Clear Well: |
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Filtered water is stored in the clear well until it is
directed through the distribution system by pumps located at the Colonel
Ward Pumping Station and the Massachusetts Pumping Station. As the water
leaves the clear well a polyorthophosphate is added as a corrosion
control. This chemical inhibits lead from contaminating the distribution
water from old pipes that our customers may have. |
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Washwater Tanks: |
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rapid sand filters are backwashed with potable water stored in our
Washwater tanks. Every time a filter is backwashed, approximately
100,000 gallons of potable water is used. |
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Backwash Process: |
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Filters are kept clean by the backwash process. Water, stored in our
Washwater Tanks, is directed through the filter from bottom to top,
while a filter sweep ( a spinning sprinkler system aimed at the filter)
blasts the filter with water from the surface. These action dislodge
dirt and debris trapped within the filter's media, cleaning the filter. |
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Equalization Basin: |
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Used backwash water and leakage are directed into a large holding vault
known as the "Equalization Basin". Water from this basin is directed
into our backwash station. |
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Backwash Station: |
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Collected backwash and leakage water is sent from the equalization basin
to a large well, known as the backwash station. Here, backwash and
leakage water is directed into our Thickeners by a series of pumps, for
processing. |
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Thickeners: |
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backwash and leakage water enters the Thickeners, a non-ionic polymer is
added to coagulate the debris. This treated backwash water is directed
to the Thickener's settling tubes, where the large surface area
encourages settling. The settled backwash is known as sludge. The
cleared processed liquid is known as decant water. |
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Thickener Decant Stream: |
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decant, produced from the thickener is directed over a weir (notched
barrier) and is allowed to enter our raw water conduit to undergo the
full water treatment process. |
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Thickener Solids Stream: |
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sludge, produced in the settling tubes by non-ionic polymer addition, is
pumped into an on-site lagoon. |
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Lagoon: |
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on-site lagoon will accept and store sludge produced in our Thickeners
and Sedimentation Basin. The stored sludge will further settle due to
gravity and the freeze/thaw process. The lagoon's decant is pumped to
the Buffalo Sewer Authority, while the sludge is processed through a
belt press or centrifuge, and trucked to an Off-Site Landfill. |