Water Treatment Plants
EBMUD's six water treatment plants can filter and process more
than 375 million gallons of water daily (MGD). The water treatment plants are
Upper San Leandro in Oakland, San Pablo in Kensington, Sobrante in El Sobrante,
and plants located in and named for Orinda, Lafayette and Walnut Creek.
The Orinda Water Treatment Plant has the largest output, with a maximum capacity of 200 MGD. This plant serves all or parts of Alameda, Albany, Berkeley, El Cerrito, Emeryville, Moraga, Oakland, Orinda, Piedmont, Richmond and San Leandro. The other plants supply water in varying amounts to the balance of the EBMUD service area.
Every drop of water delivered to customers is filtered through sand, and anthracite or carbon. Each water treatment plant also provides disinfection, fluoridation and corrosion control.
Water Treatment Steps
Aeration
Water entering the plant is sprayed into the air through
nozzles, producing a fountain-like effect. Breaking the water into small drops
creates a proper oxygen balance, releasing trapped gases that can cause
objectionable tastes and odors.
Coagulation
EBMUD adds coagulants to the water in mixing basins. The
coagulants neutralize particles, allowing them to join together. These
particles are removed in subsequent steps.
Flocculation
After coagulants are added, the water is gently mixed to cause
particles to combine and grow large enough to settle.
Sedimentation
The water flows into sedimentation basins where the
particles settle to the bottom. This step removes about 85 percent of the
suspended matter in the water. Water for the next step (filtration) is collected
from the top of the sedimentation basins.
Filtration
Any remaining particles are trapped and removed during
filtration. The almost clear water from the sedimentation basins flows into
deep, concrete-walled boxes. At the bottom are filter beds made up of layers of
anthracite and sand. Particles are trapped in these layers as the now-clean water flows down through the
filters to a
collecting system.
Disinfection
The addition of a chlorine solution kills any pathogenic
microscopic life, such as bacteria or viruses. Finely controlled amounts of
chlorine are added on an ongoing basis.
Prior to leaving the treatment plant, small amounts of ammonia are added to the
chlorine to form chloramine, a more stable disinfectant, that will last longer
in the distribution system.
Ozonation
At
Sobrante and Upper San Leandro water treatment plants, ozone is used for
disinfection and control of taste and odor causing compounds.
Fluoridation
EBMUD
is required by regulation to add a small amount of fluoride to the water to
promote dental health.
Corrosion
Control
EBMUD
adds calcium hydroxide (lime) or sodium hydroxide to the
water at the source or at water treatment plants to control corrosion. Using
lime to achieve a slightly alkaline chemical balance prevents the water from
corroding EBMUD's distribution pipes and consumers' plumbing. This keeps
substances like lead from leaching out of plumbing fixtures and into the drinking water.