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RE: Reply-Ultrafiltration to Remove Oil


Have you sent a sample of the oily water to the vendor for testing?  If he
can get it down to 20 mg/l as before, then the problem would most likely be
membrane damage as pointed out in Jacks reply. If he can't, then aging has
altered the chemical composition of the oily water. I can see this as a
cause because the vendor would have been testing a mixture of clean water
and oil. In the shop, bacteria could be breaking down the oil and forming
surfactants that further emulsify the oil.  Use of tap water, poor sump
design, and improper coolant maintenance all contribute to bacterial growth.
Good luck.


-----Original Message-----
From: wjw5@psu.edu [mailto:wjw5@psu.edu]
Sent: Friday, April 06, 2001 2:19 PM
To: Annis, Jack
Cc: p2tech@great-lakes.net
Subject: Reply-Ultrafiltration to Remove Oil


Ultration is standard technology for this application. City water should
not be a problem. An ultrafilter should eliminate all of the oil all of the
time. There must be a hole between the permeate side of the filter and the
recycle loop for that much oil to be getting through. I can think of no
other reason (unless its a microfilter instead of an ultrafilter). pH is
only important if the membrane has a preferred range and the pH of the
wastewater is something different. Silicone oils can be a problem with
ultrafilter membranes, but they would blind the filters, preventing both
oil and water from passing through, rendering the filter temporarily
useless (until it is cleaned). Oh, here's another thought. The wastewater
needs to be pre-filtered to prevent large particles such as grinding swarf
from eroding the membrane and allowing oil and other contaminants to pass
through. I can't imagine that this is the case as pre-filtration is such a
standard approach that someone would have had to blow the application
bigtime for this to occur.

Good luck.


>A company recently purchased an ultra filtration system to remove oil from
>combined wastewater stream of water soluble machine coolants, floor mop
>water, and water from buckets used for rinsing chips from parts. Company
>machines primarily aluminum and iron, maybe 95%. Minimal amounts of brass
>and no stainless or plated products are machined.
>The vendor who supplied the company supposedly ran samples of the combined
>spent coolants and wastewater through the same system prior to purchase of
>equipment and supposedly could deliver wastewater at 20-50mg/l oil
>remaining. After purchasing the system the company and vendor have not been
>able to get the wastewater below 500mg/l. Several things have been tried,
>segregating wastewater streams and running them separately, new membranes
>a different type and so on.
>The company uses city tap water instead of DI water for coolant mixing.
>Could the City water cause interference with the membranes because of
>chlorination or minerals in the tap water?
>How critical is pH range?
>I'm aware of several other technologies that will work but company would
>like to use what they have bought if possible.
>Any ideas, suggestions appreciated.
>Jack Annis, Co-Director
>Solid and Hazardous Waste Education Center
>College of Natural Resources
>UW-Stevens Point
>Tel 715-346-2793
>Fax 715-346-3624


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