If it were only that easy... We´d all love to save the planet, keep it green, waste minimize and satisfy every other buzz phrase that is now or ever was a popular reflection of the sentiment toward reuse of vital resources. "Can´t be done, though (you might be thinking) - not here in this plant anyway. Our processes are unique; our cleanliness specs are so tight that there is no way we could recycle our water-based cleaning solutions." But it is an interesting premise nonetheless, isn´t it? What if there actually is a way to reclaim all that wastewater generated from your washing operations? "Shoot, if that was possible, we have one conveyor line with both pre-clean and clean stages; we´ve got a half-dozen stand alone turntable washers, plus our pre-paint five stage. And our plating tanks, soaks and electros - what if those could be extended too? What about floor washing? Hundreds of gallons in mop buckets all over the shop... more than that from our walk-behind and drive-around scrubbers. Think of the potential savings"

Pie-in-the-sky dream or reality? The premise here is the latter.

This article´s intent is to share recycling expertise so the reader can consider equipment to recover and reuse aqueous cleaners; so, suspend any disbelief for the next few minutes while we examine the wisdom in at least investigating the concept, beginning with an explanation of the heart of the technology itself - membranes.

Membranes have been around for years, in metal working plant applications from ultra-purification of incoming water to pre-treatment prior to sewer discharge of wastewater, the two most common uses within industry. Focusing on the end-of-pipe scheme, the membrane selected often has pores that, in comparison to others that may be available, would be categorized as relatively "tight" - in hopes of removing as much as can be practically achieved without severely curtailing the speed of processing. Materials of construction differ from vendor to vendor, but, in a majority of cases, consist of a polymer "skin" surface atop a fiberglass substrate. For limited pH range and ambient temperature projects, such as either of the above would typically be, these components serve well.

However, when dealing with highly alkaline cleaners or very low pH combination phosphatizer/degreasers, especially at the elevated temperatures often seen in washing operations, they simply do not hold up. Additionally, the benefits of "tightness" prior to sewer discharge will now actually be detrimental to reuse because some of the good stuff may be removed during the processing. Membranes intended for use in recycling are not so "tight," and are typically made to thrive under conditions where others might fail.

Arbortech´s Washer Washer (small scale) and WWPro (larger scale), for example, utilize titanium dioxide membranes with a 316L stainless steel substructure. Hence, this module and others so designed can tackle applications where pH is anywhere from 0-14, at temperatures to 200F - what it often takes to recycle water-based cleaners. The mechanism for removal and concentration of the "yuck" is cross-flow (not dead end as in traditional bag or cartridge filters), pressure-driven (generated by a circulation pump) and multiple pass, with the long-term effect being that oils and soils are retained on one side of the membrane, while the water plus materials in true solution with water (like the cleaning product) pass through to the other side. With an in-line system set-up, permeate (that which passes through the membrane) is normally returned directly to the wash bath while the reject is slowly concentrated in a small (compared to the wash bath) process tank for later removal and disposal. As a result, the wash bath stays perpetually near to freshly-made-up condition and the contamination concentrates in the recycling system´s process tank instead of the wash bath, therefore requiring no (or at least greatly reduced) dump/recharge - just continual reuse.

In one unusually successful case, a company that formerly dumped and recharged its 5,000+ gallon bath quarterly before implementing a recycling system, only did so once in the next seven years... when they moved the operation out of one building and into another. While this performance is quite extraordinary, prolonging of bath life from four to six times is very common. Beyond extended bath life, what other direct or indirect contributions to the bottom line might be expected from installation of a good recycling system?

Floor Scrubber Solution Concentrate on Left Permeate on Right	Alkaline Cleaner Concentrate on Left Permeate on Right
Iron Phosphate Concentrate on Left Permeate on Right	Floor Scrubber Concentrate on Right Permeate on Left

There are nine fundamental reasons to at least consider investigation:

• Improved parts´ cleanliness
  If the condition of the wash bath is consistently high quality, the washing process will be enhanced and parts cleaned will always be at maximum purity. You know how well your bath cleans just after a dump/recharge; why not just keep it that way?
• Improved rinsing
  Typical washing operations result in transfer by carry-over of a small portion of the wash bath to the subsequent rinse stage. Where this carry-over is highly contaminated, the negative consequences at the rinse stage can be dramatic. (Review this article, Georgia Metal Finishing Initiative 2003, for an extensive case study demonstrating the kinds of results possible with recycling and counter-flowing.) After installing adequate recycling, including counter-flowing measures, rinse stages that formerly overflowed at high rates have been reduced, and, in some cases, even turned into standing rinses.
• Improved subsequent steps
  How difficult is it to paint or plate a part that has not been properly cleaned? By maintaining wash bath cleanliness, those issues often disappear.
• Increased production
  Is your wash process a production bottleneck? If so, forget about ever-shortening cycles of dump and recharge, because recycling can keep high quality cleaning virtually perpetually available. Think about your reject rate on parts... how much might it be reduced if they came out consistently clean?
• Save labor
  Do you dump and recharge on straight time or overtime? Many companies do such work after hours or on weekends, making the labor costs even greater. And how about the dollars spent addressing all the paperwork required for proper handling/disposal of the wastewater?
• Save power
  Whether you heat by gas or electricity, as your wash bath deteriorates, one common performance booster is to turn up the heat and that can be expensive.
• Save hauling costs
  When was the last time that your cost per gallon to haul this "stuff" away was reduced? Some of Arbortech´s customers have not only dramatically (sometimes by more than 98%) reduced their volumes to be hauled (obvious benefit) but also been charged less per gallon for the much more highly concentrated wastewater achievable through recycling (not so obvious benefit).
• Save water
  In portions of the world where good quality water is scarce and a precious commodity, (southwestern USA, for one example) keeping a 5,000 gallon bath in use instead of recharging it 3-4 times per year would be substantial conservation. Further, if recycling can enable a rinse overflow to be reduced, say from 3 gpm to 2 or 1 gpm, or even eliminated, what a savings in water that would be... incredible!
• Save chemistry
  Savings in chemicals ranging from 50% to 80% have been reported. How much is your annual budget for cleaning chemicals? Think that might be worth a phone call or two to companies with a recycling focus? Think your chemical vendor should reconsider that purchase of a new luxury sedan?

Some final words to the wise...

Pick your potential recycling partner carefully. Writing about the benefits of reclamation and "sales pitching" a product to accomplish this objective are both relatively easy. The willingness and ability to prove the application at your specific site, with your incoming water quality, your operating personnel, your chemicals and your contaminants are much better standards against which to measure. Vendors with capabilities to run bench scale demonstrations followed by in-the-field pilot scale testing... all done prior to your issuance of a purchase order to buy a system, may also be the ones best suited to stand up and be counted when Murphy visits you long after the final payment check has cleared.

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