|
News
CROWN
Solutions, Inc. Technical Resource
Introduction
Jim Marten - Vice President/Marketing Manager
In
this month's edition of the CROWN Solutions Inc. Technical
Resource, we discuss strategies for water minimization,
recycling, and reuse.
Water
costs and the cost of preparing water for discharge
are rising steadily with no end in sight. There are
many strategies and techniques that can be implemented
to provide immediate gains in water reduction. In addition,
the variety of technologies for bona-fide wastewater
recovery are constantly improving.
Industrial
water consumers have to consider water as a recoverable
resource. Please read on, and let us know if some of
our ideas have any interest for you.
If you have any questions, or if there is anything that
we can do for you, please contact me directly.
James
N. Marten
Vice President/Marketing Manager
Phone: 1-800-875-4075 (x) 211
Fax: (937) 898-7360
jmarten@crownsolutions.com
Figure
1: Ultrafiltration Pilot Unit
Wastewater
Recycling, Reuse, and Reduction
By James McDonald, PE, CWT
Industry
uses water to create steam, generate electricity, cool
and heat processes, clean components, or produce products.
While water can be the life blood of many industrial
processes, this same “life blood” usually becomes a
wastewater that costs money to treat or send to the
local publicly owned treatment works (POTW). Typical
industrial wastewater streams include nonsanitary streams,
reverse osmosis concentrate, softener regeneration,
ultrafiltration waste streams, process wastes, oily
wastes, and high metal content wastewater. As discharge
limitations become tighter and tighter, the costs become
higher and higher. Also, as the cost of water itself
increases, the idea of recycling, reusing and reducing
wastewater becomes even more attractive.
Wastewater
recycling is defined as treating a wastewater stream
to the point that it can be recycled back to the process
that created it in the first place. Wastewater reuse
is treating a wastewater stream to the point that it
can be reused some place else in the plant. Wastewater
reduction involves minimizing the generation of wastewater
in the process itself. See Table 1 for examples of these
strategies.
Table
1: Wastewater Recycling, Reuse, and Reduction Examples
| Recycling |
| Water
Softeners |
Brine
recycling collects the brine solution from the end
of the brining cycle and uses it at the beginning
of the next brining cycle to reduce the amount of
brine and water used for regeneration. |
| Rinse
Waters |
Removing
the offending ingredient in a rinse water with a
filter, ion exchange, ultrafiltration, reverse osmosis,
etc. may allow the water to be recycled. |
| Reuse |
| Cooling
Towers |
Waste
streams such as reverse osmosis concentrate may
be of high enough quality to use as cooling tower
makeup. With treatment such as degasification, filtration,
etc., other waste streams may be usable too. |
| Rinse
Waters |
Rinse
waters may be cascaded from one rinse bath to another
for reuse. |
| Paper
Mills |
Boiler
blowdown, softener regeneration, etc. can be used
in the pulp process to reduce the amount of water
and maybe even heat required in the process. |
| Reduction |
| Boiler
Blowdown |
Improved
pretreatment technologies such as reverse osmosis
can be used to decrease boiler blowdown. |
| Condensate
Return |
Increasing
condensate return to the boiler system will reduce
boiler blowdown, makeup water pretreatment wastes,
fuel costs, and the amount of condensate that goes
down the drain. |
| Automatic
Boiler Blowdown Control |
Maintaining
boilers at their conductivity setpoints eliminates
wide control swings that can increase blowdown unnecessarily. |
| Cooling
Tower |
Using
soft water or improved inhibition chemistries can
reduce blowdown. |
| Rinse
Waters |
Rinse
waters may be cascaded from one rinse bath to another
to reduce water usage and wastewater generation. |
There
may be many viable uses for wastewater, but each circumstance
will have to be considered separately. The basic steps
for determining if and how to recycle, reuse, or reduce
a wastewater stream are:
Figure
2: Benchtop Reverse Osmosis
1.
Identify the wastewater stream.
2.
Characterize the wastewater stream. What are the components
that make it a wastewater stream (e.g., oils, heavy
metals, dissolved solids)
3.
Identify potential treatment options, if any, which
are necessary such as conventional physical/chemical
wastewater methods, biological treatment, ultrafiltration,
degasification, reverse osmosis, and ion exchange.
4.
Identify potential uses for the wastewater. Steps 3
and 4 are interchangeable because the use will dictate
the treatment, but the treatment that is possible may
also dictate the use.
5.
Understand the process requirements for water quality.
6.
Benchtop test the treatment strategy in a laboratory.
See Figures 2, 3, and 4.
7.
Pilot test the treatment strategy live and on-site with
scaled-down versions of the treatment technology. See
Figures 1 and 5.
8.
Install the full-scale treatment system.
Conclusion
Wastewater recycling, reuse, and reduction can have
both financial and environmental benefits. Determining
if such a strategy will work at your plant requires
upfront work to ensure its success and possibly some
“outside the box” thinking. The old saying goes something
like “One man’s junk is another man’s treasure.” The
same can certainly apply to wastewater. If you have
any questions, comments, or ideas concerning wastewater
recycling, reuse, and reduction, please contact your
local CROWN Water Management Specialist.
|
|
|
|
|
Figure
3: Benchtop Ultrafiltration
|
Figure
4: Pilot Rig for Silt Density Index, Ion Exchange,
and UF Testing
|
Figure
5: Reverse Osmosis Pilot Unit
|
|
