Jack Annis asked about this situation:
"A company recently purchased an ultra filtration system to remove oil from a
combined wastewater stream of water soluble machine coolants, floor mop
water, and water from buckets used for rinsing chips from parts...After purchasing the system the company and vendor have not been able to get the wastewater below 500mg/l. "
In 1998, we sampled input and output from a Seattle area machine shop ultrafiltration unit. The shop used primarily a chlorinated soluble oil metalworking fluid (Blasocut 4000 Strong) and a synthetic grinding fluid. Tramp oil and floor mopping water also went into the ultrafiltration unit. The output results were within King County sewer discharge limits. We tested for all sorts of parameters (metals, organics, pH, FOG). The sewer limit for non-polar fats, oils and greases is 100 ppm, this shop discharged 10 ppm nonpolar FOG and had 45 ppm total oil and grease. These metalworking fluids contain millions, sometimes billions, of bacteria per milliliter. The pH was 8.3.
This shop did nothing more than turn the machine on once in a while -- it did not require lots of effort on their part to make it work. They used tap water to mix up fluid. The ultrafiltration tank area had some distinctive sulfide odors. This was not a "pristine" operation, but it still worked great for them.
Hope this perspective is helpful. Contact me if you are interested in more details about the testing data.
Alice I. Chapman, PE
King County Hazardous Waste
130 Nickerson St, Suite 100
Seattle, WA 98109-1658