Chemical Engineering May 2023 - 45

Applied Technologies
Cutting Cost and Waste with
Rinsewater Recycling
Onsite recovery conserves one of the most precious resources - water.
A well-engineered, closed-loop recycling system can pay dividends in avoided costs
to treat and discharge wastewater
Rick Hines
GF Piping Systems
I
n Southern California, few businesses
dispute the need for water
conservation. In a naturally arid
region that is also a center of industry,
it is clear that every drop of
water used in industrial processes
comes at a cost - to the environment,
as well as to the bottom line.
In short, all incentives align in favor
of responsible reuse. In light of these
facts, closed-loop water-recycling
systems can offer a cost-effective
alternative to one-time water use for
industrial processes. Such systems
can be designed for specific process
needs, and in many cases, can provide
95% or greater water recovery.
Designing the recycling system
In 2017, a manufacturer in the aerospace
sector sought a way to reduce
costs and wastewater at a site located
in Southern California. To rinse
metal parts as they are cleaned,
etched and electrolytically plated
with specialized metal finishes, the
company's operations require a high
volume of deionized (DI) water. They
therefore also produce a high volume
of metals-bearing wastewater.
A majority of this volume consists
of rinses that can be closed-loop
recycled by ion exchange in a costeffective
manner. The remainder
requires specialized treatment to
remove cyanide and heavy metals
before discharge to sewer.
During its decades in operation
before the installation of a new rinsewater
recycling system, the business
sourced all its water from the Metropolitan
Water District of Southern
California, using portable exchange
deionization (PEDI) vessels to produce
a limited volume of DI water,
at a cost of approximately $70-80
per 1,000 gal. Given this high cost,
GF Piping Systems
FIGURE 1. Water Innovations' HFX75d recycling
system, supported by process-automation
technologies from GF Piping Systems, reduced
wastewater management costs for an aerospace
manufacturer by 80%
the manufacturer only used DI water
for critical process rinses. And at
the end of the manufacturing process,
100% of the wastewater was
discharged to the Orange County
Sanitation District, after expensive
chemical treatment to comply with
regulatory discharge limits.
When the company decided to
enlarge its metal-plating operation,
they worked with Water
Innovations,
Inc. (San Diego, Calif.; www.
waterinnovations.net) to develop an
onsite system for rinsewater recycling.
Utilizing a wide array of measurement
and control instruments,
sensors and valves supplied by GF
Piping Systems (Irvine, Calif.; www.
gfps.com), the HFX75d system engineered
by Water Innovations (Figure
1) selectively recycles wastewater to
maximize closed-loop recovery of
usable water.
As described by Water Innovations
managing partner Steven Ward:
" This recycling is achieved through
the use of three different resin
systems: one that recycles up to
75 gal/min
of select
compatible
rinses; one for oxidation and removal
of cyanide from precious-metal plating
rinses; and a polishing system
with a series of specialized PEDI
vessels to remove residual regulated
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM MAY 2023
heavy metals and cyanide from the
remaining effluent prior to discharge
to sewer. " Water Innovations also developed
a proprietary bentonite reactant-treatment
system that would
allow onsite treatment of a highvolume,
oily wastewater stream. In
total, the volume of wastewater requiring
chemical treatment before
discharge has been reduced by
over 60%.
Water recycling gets results
With the new system providing an
abundant supply of DI water (and
with the cost per gallon reduced by
about 70%), the aerospace company
has been able to expand the use of
the system to a wider range of rinse
processes, with a positive impact on
product quality. Meanwhile, compared
with the process of purchasing
water, using it once, waste-treating
and discharging to sewer, the
business' investment in closed-loop
rinsewater recycling with segregated
waste treatment has brought down
their overall wastewater-management
cost by approximately 80%,
the company says. The recycling
process produces DI water at a cost
of $5-6 per 1,000 gal - a significant
improvement over their previous
cost of $70-80 for PEDI purification
of potable water. Given that disposal
expenditures were greatly reduced
as well, the company achieved return
on its Water Innovations investment
in approximately two years.
As of November 2022, assuming
HFX75d operation at 75 gal/min,
for around 100 h per week, since
startup in March 2017, this aerospace
supplier had recycled (and
therefore avoided discharging to the
publicly owned treatment works) an
estimated 120 million gal of water.
For nearly two decades, Water
Innovations' water recycling and
45
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