Gaps in Aqueous
Efforts to better understand and document the successes of aqueous cleaning are
ongoing. Several areas that merit future study are:
- Extending the life of aqueous cleaning solutions using closed-loop
approaches. The use of oil skimmers or similar equipment to remove large quantities of oil from aqueous cleaners is widely used and well known, but more sophisticated approaches such as membrane filtration are still not fully understood by many manufacturers. To date, the majority of work done to extend cleaner life has been done within private companies, and has not been made publicly available. Some work has been done recently. For example, Underwood and Thomas reviewed the concepts and techniques for closed loop aqueous cleaning and presented three short industry case studies where filtration was used to extend the life of aqueous cleaners.
(Ref. 16) In one example, a metal parts manufacturer reduced daily wastewater discharge due to cleaning from 2,000 to 75 gallons by installing a cleaner recycling system that uses hollow fiber ultrafiltration. Additional applied research and documentation of industry experiences is necessary to provide an available knowledge base to help manufacturers reduce the wastewater streams they generate as a result of aqueous cleaning. Extending the life of the cleaning solution will reduce both cleaning purchasing and wastewater treatment costs.
- Obtaining a better understanding of temperature's effect on the aqueous
cleaning process. The significance of
temperature in aqueous
cleaning was discussed in the technical section of this review, but several
important questions remain unanswered. Why did some experimentation show that
operation at temperatures above the cloud point resulted in higher cleaning
efficiencies? Is this finding, which contradicts conventional wisdom, true for
cleaning solutions other than those already tested? Gaining a better
understanding of the effects of temperature will allow manufacturers to operate
their cleaning processes more efficiently.
- Ongoing development of cleaning solutions that are biodegradable
This issue of cleaning solution biodegradability was briefly mentioned in the
of this review. Increased biodegradability of cleaning solution will reduce
treatment requirements for spent cleaning solutions, as long as non-biodegradable
contaminants added during cleaning are separated from the solution or can be passed
on to the discharge point (sewer or surface water).
Continue on to the summary page of the Aqueous Cleaning Technology Review.
- Additional case studies of manufacturers' efforts to implement and
improve aqueous-cleaning systems. Continued documentation of industry
experiences in this area are essential to promote the transfer of information
between companies as continued improvements are made by individual manufacturers
in their aqueous-cleaning processes. More detail regarding the experimentation
with key cleaning process parameters that many companies do to implement a
new system would be useful to include in these case studies. Ultimately, what
does and does not work in the manufacturing environment will be defined by
manufacturers themselves, and continued transfer of this knowledge will reduce
the number of companies that waste time when trying to implement or improve their
own aqueous-cleaning process.
Return to the introduction of the Aqueous Cleaning Technology Review.
© 1999, Pacific Northwest Pollution Prevention Resource Center
phone: 206-352-2050, e-mail: email@example.com, web: www.pprc.org