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| Posted on 3/20/08 at 05:45 AM | |
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Interesting thought, but lets add a little to this. Lets take a look at pure photopolymer emulsion for a second. Great stuff, but generally its used because the shop using it has a weak exposure lamp and can't use the cheaper dual cure emulsions. Pure photopolymer emulsions have the habit of cross linking in the screen when you use organic solvents as a press wash (this includes most screen openers, xylene based thinners etc.) This makes the emulsion harder to get out. Its more of a crystalline debris. It stops up pipes in a great many shops. Simply going to a better lamp could result in less solids in the waste stream. Yeah its more expensive for a good lamp, but at $20 less a gallon in some cases you can pay the difference in that lamp cost in the first year. The polyvinyl alcohols and polyvinyl acetates of emulsions tend to conglomerate in waste streams with all kinds of chemicals. It may actually be that you are doing more damage to city plumbing systems than actual damage to the environment. That being said, having to use a ton of periodic acid (the base chemical of emulsion removers) drops the PH so low that you may also end up killing off a great deal of beneficial bacteria that help break things down in the sewage system. Lots of angles to worry about. What could alleviate most of this is what was being discussed in another thread last week. Filter what comes out of the reclaim sink. Its not that hard and not very expensive. You need to get a idea of how many gallons per day you use of combined water and chemicals. Build 2-3 tanks, drums , pits...whatever....containment vessels. Plastic chemical drums work great. You need covers. You will need a small sump pump. Water comes from sink, goes to first tank passing through a strainer to settle out heavy solids. It comes in from the bottom or middle of the tank. It only gets out by flowing over the top edge through a pipe into the second drum (its called a weir). It flows through a simple mesh filter to grab any floating debris and the last of the tape etc. This second drum could be outfitted several ways. Either a heavy wire rack on feet holding about a foot of pea gravel and sand,or a fiber filter element on the shelf. The pea gravel and sand method allows you to backwash out the solid crud every couple weeks into a covered trough where you let the water evaporate, scrape up the solids and put it in a disposal drum. The water exits this second drum from the bottom. At this point you will usually find the water decently clear but a little murkey. It can go to the sewer. Congratulations! You just created the equivalent of a 1940's swimming pool filter. It takes most solids out. If you really wanted to be creative and obsessively green (though this is not necessary really)....you can have a third tank that you dump a little bit of Muriatic acid in (swimming pool acid). The drop in PH will generally precipitate any small solids out and they settle to the bottom...rapidly. Or...get a common pool floculant and add an ounce or two. This will floculate all of the almost microscopic solids into big visible ones in about 30 minutes so that they can be caught by filters as simple as the sand filter you built or a simple sock filter. The real issue here is that there will be some maintenance to be done. Not a lot, but about the equivalent of running the chemicals and filters on your own home swimming pool (minus the vacuuming). The question remains to be seen as to whether the average shop owner will invest the effort. Commercial systems like this have been mandatory in Californis for some time. Companies like CCI chemicals have made turnkey systems that use vitreous clay media and bag filters to do this work...for eons. The stuff you need to be green has been out there for decades. Just that until now...few people have taken the initiative. My advice is to do it now. Do something! Once you get a system in place...almost any system, get into the routine and plan the cost overhead into your product, it will become a part of daily life. Because...not far off (and remember someone told you this)...you will be forced too by LAW. The more you do now, the less they will force you to do later.... because you displayed due diligence in taking preemptive corrective actions. It will be cheaper now than when everybody needs it. Ray | ||
 
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