Texas Instruments
(TI) has found that developing water balance
diagrams that map water inflows, outflows and intermediate
reuse between production and support areas in a manufacturing
plant provide valuable information for improving water
management and reducing costs. A water balance is very
beneficial during the design of manufacturing plants
as well as during efforts to optimize subsequent plant
operations, particularly where appropriate flow meters
are installed. Identifying the amount and quality of
water needed in all (or major) water use areas allows
the development of a better-integrated water use program
during process design that may reduce demand for freshwater.
A water management system can also match water use requirements
with other water streams in the facility of appropriate
quality, enabling reuse without additional treatment.
TIs semiconductor fabrication
plant in Miho, Japan has been in operation since the
early 1980s as a zero industrial wastewater effluent
plant. The plant was built this way at the request of
the local neighbors and government. At the time, the
area lacked the infrastructure to support a more conventional
plant design, which typically uses over a million gallons
of water per day. The production area at the Miho plant
reuses process water over and over again, enabling the
plant to consume a much smaller amount of water than
comparable semiconductor plants. Some generated production
byproducts are segregated from process water
and collected for reuse as raw materials at other companies
or disposed of as concentrated waste solutions.
The Miho plant has found water balances
to be useful tools for improving process designs and
communicating about water use. A sample water balance
for the Miho plant is shown below.

Miho
Water Balance
The complexity of a water balance
depends on the type of facility and the characteristics
of the local area. A site with only a few water use
requirements might need only a simple water balance
prior to starting a water management program. For a
complex site with many water uses, an accurate site
water balance should consider seasonal impacts as well
as water use at various production rates. For example,
at the Miho plant, and a similar plant in Hiji, Japan,
there are actually many water pipeline interconnections
between areas to minimize water use. Many of these connections
at the Miho and Hiji plants are measured on varying
frequencies to assure gains are being maintained and
to identify additional opportunities.
Using an accurate water balance in
a sound water management program can improve:
- Identification of current and future
water uses
- Consideration of water conservation
opportunities during the plant design phase
- Ability to troubleshoot problems
during actual plant operation by using flow meters
to compare actual water use with plant design
- Identification of water reuse opportunities
during plant expansions
- Identification of other future
cost-effective water conservation projects
- Ability to communicate water use
issues within the company and to external critical
customers

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