Apr 12, 2006

Alternative Solutions for a Sustainable Future

According to a recent World
Bank report, 300 million people
live in areas with serious
to severe water shortages, and this
number could reach three billion
within 25 years. The option of tapping
into alternative water resources
continues to be explored as the
demand for water increases.
Population growth, environmental
pollution, infiltration of saltwater into
aquifers and the increased cost of
wastewater disposal are some of the
key reasons why membrane technology
is being utilized to resolve these
complex issues.

An increasing number of water
and wastewater treatment facility
managers are incorporating membrane
filtration technologies into their
treatment systems because of the
many advantages of membranes.
These advantages include greater
automation, smaller facility requirements,
reduced chemical use and
environmental impact, and high-quality
results. For drinking water, membranes
provide a high level of treatment
that often can’t be attained by
other technologies.

American Water is investigating
new ways of supplementing traditional
treatment approaches with
efficient, cost-effective and
advanced technologies to meet its
customers’ needs.

For example, membrane treatment
is being applied in small community
developments to provide
high-quality, decentralized water and
wastewater treatment utilizing automated,
computer-controlled systems.
Wastewater treated by such membrane
processes is increasingly being
reused for irrigation, sanitation and
groundwater replenishment.

The brief case studies that follow
illustrate the various applications of
membrane filtration technology for
treatment of potable water and
wastewater, and for water reuse.

Potable water treatment

Four Seasons, Chester, N.J.

At Four Seasons at Chester, a senior
community in Chester, N.J., treated
water is discharged into the
aquifer. This helps maintain a plentiful
groundwater supply in the local
environment. The Applied Water
Management Group of American
Water designed and built the facilities
and now owns and operates them
for this community.

Potable water plant, Anthem, Ariz.

The Anthem Water Treatment

Plant receives water from the
Waddell Canal, which connects the
Central Arizona Project Canal and
Lake Pleasant. Surface water from the
Waddell Canal is drawn through a
trash rack and pumped to the
Anthem Water Campus through a
30-in. diameter pipeline that is
approximately 8.8 miles long.

At the water campus, the flow is
directed into the raw water storage
reservoir. From the reservoir, the water
enters the raw water pump station
wet well where submersible pumps
convey the water through a strainer
and influent meter to the membrane
filtration (MF) process tanks. The MF
system has a maximum design capacity
of 7 mgd and utilizes ZeeWeed
membrane technology by Zenon
Environmental, Inc.

After treatment by the MF system,
the permeate pumps deliver the
water through a treated-water meter
and into two finished water storage
reservoirs. A UV disinfection system,
followed by chlorine contact tanks,
serves as the primary disinfection
process for the plant.

Wastewater treatment and reuse

Wastewater plant, Anthem, Ariz.

Arizona American Water’s Anthem
wastewater treatment facility is a
3-mgd membrane process plant
that began operation in 1999. It
produces an extremely high quality
Class A+ effluent for reuse—the
highest standard designated by
the Arizona Department of
Environmental Quality.

Plant effluent is used for irrigation
at a local park, two golf courses,
highway medians, community landscaping,
aquifer recharge, and it is
sold to contractors for spray application
to control dust. The plant has
been constructed in three distinct
stages to meet the needs of a growing
community, and it is in the planning
stages of a fourth expansion.

At its headworks, the plant is
equipped with a screenings grinder
followed by a perforated 2-mm
screen with screw conveyor and
vortex grit removal system. The biological
treatment design is similar to
a normal wastewater plant design,
except that the anoxic zone is
increased. This is done to account
for the long sludge age of the system
based on a biological nutrient
removal process that will nitrify and
denitrify the wastewater to meet the
permit effluent criteria. The purpose
of the membrane system is to filter
the water from the bioreactor mixed
liquor suspended solids.

The membrane treatment
process is capable of producing a
filtrate meeting the permit requirements
for suspended solids, turbidity
and total nitrogen in a smaller
space than other conventional
alternatives. The system utilizes a
ZenoGem system, which incorporates
hollow, fine-fiber membranes
in an “outside-in” flow configuration.
The flow, provided by suction
through the membranes induced by
the permeate pumps, draws the
clear water through the membranes
at pressures ranging from -0 to -9
psi. The filtrate from the membrane
bioreactor system is sent to the
chlorine contact basin or an inline
UV system and then to the storage
reservoir. From the storage reservoir,
the effluent is pumped to
the reuse distribution system.

Sustainable water management

Membrane technology has
helped American Water prepare
for a future when freshwater supplies
across the country and the
world will be less readily available.
It is critical that alternative solutions
are investigated today for
a sustainable future.

About the author

Mark W. LeChevallier, Ph.D. is director,
innovation and environmental stewardship
for American Water. To find out more,
contact American Water at 856/346-8200
and ask for business development.