Chemical Engineering April 2023 - 51

EVWD
FIGURE 2. Municipal water providers certainly serve many different end users than the industrial sector,
but the key lessons related to conserving water and minimizing system bursts and leaks are crucial for
all water suppliers and users
exact location of a leak can be identified,
allowing for monitoring and repair
before the leak deteriorates into
a burst.
Industrial water use and loss
It is estimated that industrial water
use represents about 5% of total direct
water withdrawals (surface and
groundwater sources) in the U.S.
(around 18.2 billion gal) and 12% of
the public water supply. Among the
most water-intensive industries are
agriculture, biotechnology and pharmaceuticals,
metals and mining and
forest products.
Leaks can represent a significant
economic factor for an industrial
facility. For plants relying on public
water supply, the cost of water includes
not only the price of incoming
water and the sewage fee for
discharge, but also the cost incurred
through any treatment or processing
(typically for chemicals and energy)
that a plant carries out for its own
purposes, plus associated labor and
other costs. The full cost of water
can end up being three to four times
the cost charged by the utility.
Moreover, industries operating in
water-stressed areas of the world -
the southwestern U.S., for example
- likely will be facing a changing
regulatory landscape with regard
to acceptable water use and loss,
making leak detection and elimination
a critical element in any industrial
water strategy.
Companies can begin the process
of determining water loss and
potential leaks with a water-balance
calculation, or a comparison of input
versus output, considering such factors
as evaporative loss, input to
product streams and wastewater
discharge requirements. When output
is shown to be less than input,
a leak may be the culprit. Effective
pressure and acoustic monitoring
can help industrial facilities to avoid
the loss of a tremendous amount of
water and associated expense.
Use case: EVWD
East Valley Water District (EVWD;
www.eastvalley.org) provides water
and wastewater services to 103,000
residents of San Bernardino County,
Calif. (Figure 2). EVWD staff felt that
evaluating the existence and severity
of pressure transients was a prudent
step in actively managing its waterdistribution
system. The main goal
was to reduce line breaks caused
by pressure transients, aging assets,
bedding failures and corrosion. With
the cost of repairing
a single break ranging
from $10,000 to
$25,000, reducing
these events can
generate
to
significant
deploy
a
savings. EVWD decided
network-calming
project
using smart
pressure monitors.
To identify critical
areas, the team
imported
EVWD's
historical data on
breaks and combined
this with geoCHEMICAL
ENGINEERING WWW.CHEMENGONLINE.COM
South East Water
FIGURE 3. Pressure monitoring data were used to pinpoint the location
of a simulated leak
APRIL 2023
51
graphic information system (GIS)
data using open-source GIS software
to create a map of " hot spots "
of concern associated with specific
pressure zones. Possible transient
sources - such as pumps, valves
and user points - were then identified
near each hot spot. Using this
water-main-break heat map, pressure
monitors were deployed at
pumping stations and on hydrants
across the network to confirm
transient propagation across the
monitoring area.
To cover the entire service area,
the monitoring project was undertaken
in phases, focusing on the
most critical areas on the heat map
first. To identify transients of concern,
two types of data were analyzed,
as described below.
Summary pressure data. This is
a summary of the minimum, mean
and maximum pressure values registered
over a period of 1 or 15 min
based on constant readings at 128
samples per second, also known as
high-sample-rate data.
Pressure sensitivity data. A pressure
sensitivity threshold, known as
an S3 score, was set in each pressure
monitor to alert when transient
events occur. S3 scores are a nondimensional
measure of pressuretransient
activity calculated within
the unit
itself. Large and sudden
changes result in a high score; small
changes over a longer period result
in a lower score. Tracking and
profiling pressure sensitivity data
is a good measure of the pipeline's
transient
activity, indicating
if
the
activity level has increased or if mitigation
work has been successful in
reducing it.

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Chemical Engineering April 2023

Table of Contents for the Digital Edition of Chemical Engineering April 2023