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bioremediating parts washers
- Subject: bioremediating parts washers
- From: Karl DeWahl <email@example.com>
- Date: Mon, 22 May 2000 13:48:41 -0500
- List-Name: p2tech
- Organization: MnTAP
- Reply-To: Karl DeWahl <firstname.lastname@example.org>
1. We have some anecdotal information that confirms what John Katz found -
bio-parts washers remove oils pretty well but they are slow at removing
These are intended to be long-lived parts washers if they are maintained.
This reduces the importance of whether the solution is hazardous or not.
If there is no waste, whether the solution contains hazardous constituents
only matters in terms of worker exposure and potential spills. I would
expect the heavy metals concentration to equilibrate at some point. Solids
would need to be removed. I have not seen biowashers with good means of
dealing with solids. The solids would likely be hazardous.
2. A variation on long-lived aqueous washers is the Circuit Research
"Cleanwise" system, 763-479-3662. The cleaner is intended to last
indefinitely but in reality, with carry out, the solution is completely
turned over in 6-9 months. There are a number of cases here where there
has been no aqueous cleaners waste yet in 4 years of operation, and no
reason to expect any in the future as long as the washers are maintained
The washer maintenance is elegant. There is a skimmer to remove oils (used
oil), and solids are removed in an automotive/truck type oil filter. It is
believed that most of the heavy metals in solution don't have time to
transport to the aqueous phase before they are skimmed off with the oil
phase. In Minnesota used oil and oil filters are managed as wastes exempt
from hazardous waste rules as long as they are recycled. The filters go as
scrap metal along with other oil filter waste.
These washers also work well at removing oils, but are typically 20-30%
slower than mineral spirits at removing grease.
The Minnesota Office of Environmental Assistance gave CRC a grant in 1995
to study the solution over time. I suspect the results would be similar for
other aqueous solutions that are designed to last indefinitely for
automotive repair applications. Over a 1.5 year study, oil and grease
levels were typically in the 2000 mg/l range with some spikes of up to 10
times that level.
BETX remained at less than 5 mg/l except for 2 higher spikes. In neither
case was there any tendency toward concentrations climbing.
Metals also fluctuated substantially over time. Lead was the only species
problematic from the point of view of hazardous waste rules. The highest
lead level observed was 12.8 mg/l, the average concentration was 4.2 mg/l
and the year and a half test ended with a lead concentration of 0.6 mg/l.
Cadmium was never observed at concentrations higher than 1.1 mg/l. Chrome
concentrations were never observed higher than 1.2 mg/l. In terms of
possible wastewater considerations, the copper concentration averaged 9.3
mg/l with a high concentration of 25.8 mg/l, while the average zinc
concentration was 87 mg/l with a high of 124 mg/l.
3. I wouldn't classify the system one parts washer as either aqueous or
bioremediated. My understanding is the washer uses mineral spirits and has
a built-in still to recover the solvent. Anecdotes in this area are that
it cleans well (fresh solvent is almost always available for use), but the
standard unit is small for many operations and can easily be overwhelmed
with soils in a large or busy shop.