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RE: Treatment of Wastewater for Reuse; Flexo Printer (2)


I agree with Mike Callahan that a UV/ozone generator would be an
alternative for biocide and may be the only alternative if your clients
products are for packaging food or drug industry products. You can probably
find some vendors in the Thomas Register. On the other hand, I doubt that
your client will be able to maintain conditions in his plant which will
negate the need for some means of biological activity control. The problem
is 1) the lapse between generation of the wastewater and its reuse, 2) the
ambient conditions of the wastewater during processing, storage and reuse
(warm, humid environment), 3) the fact that starch and the organic
components of water based flexo inks are an excellent food source for
bacteria, 4) the fact that none of the starch or flexo ink components
(other than the biocide most flexo ink manufacturers add to their products
specifically for control of biological activity) are highly toxic to
bacteria and 5) the fact that, whether continuous or batch, the treatment
process does not lend itself to complete removal of the components
favorable to bacteria at anytime during their operation.

Given this, bacteria will rapidly reproduce and can, even if you were to
start out with sanitary conditions, reach a colony count high enough to
consume most of the food source (starch, etc.) within about 2 weeks. To
avoid this and the detrimental effects of the bacteria on the client's
gluing operation, every square inch of the system would have to be cleaned
weekly or even twice per week with a bleach solution or other biocide.
Because all systems have blind spots, dead corners and other impediments to
complete cleaning (even if totally enclosed), this is a physical
impossibility. Therefore biological activity will have to be controlled
with a formaldehyde based biocide or, as Mike suggested, a UV/ozone system.

Hope this is useful.


>Start with the water handling system.  Look for dead legs where sludge
>can collect.  These areas will breed bacteria.  For the entire process,
>think sanitary.  Can you hard pipe to holding tanks ?  Shops that use
>the floor drains to convey wastewater will never maintain sanitary
>What about worker habits ?  Do they smoke or eat in the shop ?  Do they
>spit into open trenches ?  Eliminate these sources of contamination and
>you will be able to bring bio growth under control.
>In terms of treatment, a small UV/ozone system should help.  Biocides
>may be used but there may be restrictions if the paper can come in
>contact with food.  UV/ozone is nice because it does not generate
>chlorinated by-products.  Its downside is that there is little long-term
>protection provided to the treated wastewater.  That's why maintaining
>sanitary conditions is important.
>Just some thoughts,
>> ----------
>> From:         Wayne Pferdehirt[SMTP:pferdehi@epd.engr.wisc.edu]
>> Sent:         Wednesday, February 04, 1998 12:29PM
>> To:   p2tech@great-lakes.net
>> Subject:      Treatment of Wastewater for Reuse; Flexo Printer
>> Would appreciate any suggestions that might help a flexographic
>> printer that UW is assisting decrease wastewater:
>> The company is a flexographic printer, manufacturing primarily
>> printed kraft paper bags (grocery sacks, take-out bags, etc.)  All
>> inks used are water-based.  The company is not connected to a
>> municipal sewer system.  Only sanitary wastes are discharged to the
>> on-site septic system; other wastewater must be trucked to a municipal
>> wastewater treatment plant, at considerable expense.
>> There is considerable wastewater from cleanup of the paste makeup and
>>  cooking operations, and from ink cleanup.  Presently, wastewater is
>> pretreated through precipitation and vacuum drum to remove solids, and
>> effluent is trucked to wastewater treatment plant.
>> The company would like to increase its reuse of wastewater.  They
>> tried in the past, but said that remaining bacteria in the wastewater
>> caused problems with paste makeup.  Said the bacteria caused the paste
>> to break down and lose strength.
>> Any experience and suggestions from P2Tech users that might help
>> identify improvements that would help company to successfully treat
>> wastewater to enable reuse for paste makeup?
>> **********************************************************
>> Wayne P. Pferdehirt, P.E., AICP
>> U. of Wis., Solid & Hazardous Waste Education Center
>> 610 Langdon Street, Room 529, Madison, WI  53703-1195
>> Phone:  608/265-2361     Fax:  608/262-6250
>> pferdehi@epd.engr.wisc.edu
>> **********************************************************


Warren J. Weaver
227 W. Market St.
York, PA 17401

fax 717-854-0087

ph 717-848-6669

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