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Jeff:<br>
<br>
Although we don't have an identical system, we do use a reclaim
water system. While I'm not sure that I can offer a great solution,
I can tell you that your description of the problem as a "brown,
slimy, stringy, substance" really sounds very similar to what we
have seen.<br>
<br>
Let me describe for you and others what our reclaim water system is
like:<br>
<br>
Our two, big 25,000 CFM building scrubbers consume something like 4
GPM ... which, as you know, is a lot of water over the course of a
month. To reduce "one-time-use" of industrial water in that system,
we have a system that pumps the output of our acid waste
neutralization tank (as long as the pH is between 5.5 and 10) to the
scrubber and uses that water as the makeup water for our two
scrubbers. The feed into our AWN system includes waste chemicals
from our wet bench cleaning stations (note: things containing HF are
collected in a separate tank/drain system), DI water once it have
been used, and industrial water from a handful of small, local
tool-specific burn boxes and scrubbers. Although we tried it at one
point, we no longer try to reclaim RO reject water.<br>
<br>
In the early months of this year, in particular, we were seeing a
significant buildup of a "brown, slimy, stringy substance" in the
sump of our main scrubbers that was clinging to the walls, clogging
the inlet to the spray pumps, etc. While I think that you may have
done more scientific analysis than we to identify this stuff, we
were wondering whether some of our wet vacuum pumps (we still us a
significant number of wet pumps) were "belching" pump oil vapors
that were collecting in our scrubber system and causing this
problem. While we never convinced ourselves that there was any
validity to our pump oil vapor hypothesis, we certainly did see a
build up of a material that sounds a lot like what you were seeing.
It was sufficiently severe that we had to schedule a mid-year
shutdown of the scrubbers to have them cleaned. Although I'd need
to check some records to be sure, that is the time of the year when
we often get a higher fraction of ground water mixed into our
supply. Most of the year, the water that we get from the Hetch
Hetchy water system is pretty good, produces minimal scale, is easy
on DI systems, etc ... but during the winter months we often get a
higher mix of ground water that necessitated more frequent resin bed
changes, etc.<br>
<br>
So, while I can't offer you a solution, I think that we have seem
something that sounds very similar to what you are experiencing and
would be eager to coordinate our efforts to help further study this
and come up with a good solution. I've cced our building facility
engineer as well as some of our lab senior technical staff in hopes
of making them aware of this discussion. You are welcome to send me
email directly if there is any need for further off-line discussion,
comparison, and brainstorming.<br>
<br>
Thanks,<br>
<br>
John<br>
<br>
<br>
On 10/3/2012 10:16 AM, Kuhn, Jeffrey G wrote:
<blockquote
cite="mid:D14ADF941D26CD4E9015A15C62B39556A918260483@VPEXCH06.purdue.lcl"
type="cite">
<p class="MsoNormal">Good Day All,<o:p></o:p></p>
<p class="MsoNormal">The campus water supply at Purdue is quite
hard. As a result, we have seen a significant buildup of scale
in our exhaust scrubber, liquid ring vacuum pumps, and burn
boxes. This required periodic shutdowns to remove the scale,
which was expensive and time consuming. We have since installed
a water reclaim system to capture RO, ultrafilter, and EDI
reject streams for use as makeup water for the systems mentioned
above. The water from those waste streams has been softened,
thus we eliminated the scaling issue.<o:p></o:p></p>
<p class="MsoNormal">Unfortunately, in solving the scaling issue
we have created a new problem. A brown, slimy, stringy,
substance builds up in the storage tank. It clings to the tank
walls, peels off in sheets, and gets pumped to the points of use
where it causes fouling. It settles to the bottom of the storage
tank and coats the tank walls and process piping. We have to
semi-annually drain and clean the tank to prevent severe fouling
at the points of use.<o:p></o:p></p>
<p class="MsoNormal">We have verified that the material is not
viable (I was surprised by this). Analysis shows that it is
primarily comprised of iron. Purdue uses ground water that is
high in iron for its potable water supply. In order to protect
the water distribution infrastructure, a monophosphate-based
agent is added to the water in order to sequester dissolved
iron. This helps prevent the iron from oxidizing and
precipitating inside the piping system. It would seem that their
sequestering agent is strong enough to prevent the dissolved
iron from being completely removed by IX in the UPW system
softeners. <o:p></o:p></p>
<p class="MsoNormal">My belief is that dissolved iron becomes
concentrated at the RO in the reject brine stream and then
oxidizes in the storage tank, combining with phosphate to form
the slime we are seeing. I do not believe the ultrafilter or EDI
loop reject streams are major contributors to the problem due to
the high purity of these waters. We do not have enough
information yet to prove or disprove my theory.<o:p></o:p></p>
<p class="MsoNormal">I realize that this is a rather unusual
problem, but I was hoping that some of you may also have
installed reclaim water systems and can provide some insight as
to how to deal with this issue. We are considering installing a
filtration system, but it is expensive and I am not yet
convinced that it will solve the problem. <o:p></o:p></p>
<p class="MsoNormal">Thank you in advance for your feedback.<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom: 0.0001pt;"><span
style="font-size: 12pt;">Jeff Kuhn<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-bottom: 0.0001pt;">Facility
Engineer<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom: 0.0001pt;">Birck
Nanotechnology Center<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom: 0.0001pt;">Purdue
University<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom: 0.0001pt;">1205 W.
State St.<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom: 0.0001pt;">West
Lafayette, IN 47907<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom: 0.0001pt;">Ph: (765)
496-8329<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom: 0.0001pt;">Fax: (765)
496-2018<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
</blockquote>
<br>
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