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bioremediating parts washers





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 
grease.
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 
properly.
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.