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Aqueous cleaner water disposal

mk

#21332

Aqueous cleaner water disposal | 27 August, 2002

Our company uses a conveyorised aqueous cleaner to wash printed circuits after water soluble solder paste is reflowed. The system is closed loop with carbon and resin filters.

The water eventually will get dirty. Can it be dumped? Treated? How do you get rid of the old water when it is time to clean and refresh the machine?

mk

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#21333

Aqueous cleaner water disposal | 27 August, 2002

We use an evaporator, so that we only have a sludge of flux residue and solder metal to dispose of via the hazmat handling service. We also route stencil washer waste water into it. We use a 30 gallon drum and have it hauled off maybe twice a year, about half full. I'm afraid if we wait any long the bottom will drop out of it when they lift it. (eek!)

You could also have them take away all your waste water in drums, although that sounds horrendously expensive.

I *think* there are very efficient filtration systems available as well, but I haven't looked into them, nor have I speculated much on how they work. I would surmise that you'd either clean the filters and call your local hazmat disposal service to haul off the dregs, or just have them pick up the disposable filters. Maybe someone here is using one of those systems and can fill you in...?

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Mike Konrad

#21334

Aqueous cleaner water disposal | 27 August, 2002

MK,

In most cases, if the machine is completely closed-looped (prewash, wash, prerinse, rinse, final rinse etc), then the water should not require changing. As with most inline cleaners, there should be a considerable amount of water loss in the cleaner due to evaporation. This loss requires an equivalent volume of make-up water to be added to the cleaner. Between the carbon and resin system removing organic and ionic contaminants, and the normal water attrition caused by evaporation and make-up, the need to change the water is normally eliminated. A closed-loop cleaner should be closed-loop. A closed-loop cleaner that requires the draining of water is only partially closed-loop.

There are some conditions that may prevent a fully closed-loop environment. If chemicals are added to the wash water and it is segregated from the closed-loop rinse section, then the wash water will require discharge. As previously suggested, an evaporator will reduce the volume of waste water by many times. Eventually, the �sludge� created by the evaporator will need to be hauled away as hazardous waste. There are methods of treating the waste water prior to disposal but then you become a �treatment center� and are subject to strict permitting and regulations.

Mike Konrad

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dragonslayr

#21398

Aqueous cleaner water disposal | 3 September, 2002

All valuable insights are provided by the other posters to this thread. I'd like to add a bit more, if I may.

Being environmental friendly is a must. I would not advocate dumping toxic metals to the sewer.

In a past worklife, a steel mill, I was responsible for the continuous monitoring of the waste water treatment plant. I had a lab that used an Atomic Absorption analyzer and tested for 6 heavy metals. As long as our waste water was within the safe limits (i.e. loww ppm's) we could dump to the sewer and meet Federal, State and local safety standards. This occured in the SF Bay Area.

I suggest you find out through the local municipal waste treatment plant what the standards are for your area. An outside lab can test your water for the critical metals, usually about $50 per metal tested. If your waste is less than the standard, consider pumping a low volume (20 gals or less per day) to the sewer. Be sure your pH is balanced if dumping to the sewer, a ph that is too acidic will eat the concrete sewer pipes. That would be very costly to replace, the hazmat fees for removing your waste water is significantly lower in the long run. Depending on where you are, your local weaste treatment facility may be able to test a water sample and give you an indication if it is a safe idea to dump to the sewer.

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mk

#21446

Aqueous cleaner water disposal | 7 September, 2002

I agree but, are there really heavy metals in this water? Our process is as follows.

Print Paste Reflow Board (no components, water soluble paste only) Wash Board

Same reflow profile for almost every order so no solder balling issues etc. Carbon and Resin filters. Is the heavy metal still a concern? What's in that sticky stuff left over after reflow?

mk

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dragonslayr

#21459

Aqueous cleaner water disposal | 9 September, 2002

Your lack of obvious solder balls indicates you have a decent process. However, there are still small solder balls that are free and floating on the surface of the boards prior to wash. That same solder ball is washed off and ends up in the wash solution or filter traps. Therefore, you will have lead and tin in your waste. It is most likely not broken down to the molercular level and attached to the H2O molecules. Yet, it would be prudent to verify the actual concentration of heavy metal in your waste stream. If you can dump to the sewer and be in compliance, that would be a good thing.

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#21460

Aqueous cleaner water disposal | 9 September, 2002

Around here that opens you up to some financial liability if ANY lead is found in the sewage, if they can't pinpoint the source. Every user over X lbs./month (dunno the specifics, just got this from our hazmat guy) is on the bubble for anyone else's waste if it can't be tracked.

Just be sure you understand what your potential liability is if you're pumping a potential source of hazmat into the local sewer system.

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dragonslayr

#21461

Aqueous cleaner water disposal | 9 September, 2002

steve- once again I mention that the lead that is actually in the water is in solution i.e. the lead is in a molecular form that has attached to a H2O molecule.

To have a minimum of lead that is below the regulated ppm, there cannot be any chunks, solder balls etc. The DI water rinse beds, the water wash filters should be trapping and eliminating the potential of lead getting into the final waste stream. Most PCB assembly processes do not have the capability of reducing the lead to molecular level. That condition would require high heat, caustic acids, etc. all of which would destroy the materials far before a useful product would be produced.

If your local regulatory agency is finding lead in the sewer is because some company is bypassing the approprite filtration prior to dumping to the sewer.

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