Printech Archive, February, 1998
Re: Treatment of Wastewater for Reuse; Flexo Printer

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From: Wayne Pferdehirt (
Date: Thu Feb 05 1998 - 09:50:13 CST


The company should consider a membrane filtration wastewater treatment
system. To remove virtually all of the contaminants (and perhaps
without abandoning their present treatment system) they could add a
reverse osmosis system. Also, depending on the contaminants remaining
after treating with their existing treatment system, they may be able
to inject a biocide into the cleansed wastewater prior to reuse
without otherwise modifying the system. This is common practice with
flexo newspapers where ultrafiltration is standard treatment followed
by biocide feed and reuse as diluent for the flexo inks. They should
check with their ink supplier for recommendations on biocides as they
may have experience in this area (Flint and Sun Chemical do for sure).

Their present system sounds like an Alar system. My clients have found
that the diatomaceous earth used to coat the vacuum filter gets
"pinholes" in it and allows filterable solids to pass through, albeit
in small quantities. Nevertheless, it has prevented them from meeting
pretreatment standards and causing them to abandon their systems in
favor of either ultrafiltration or evaporation. Evaporation is another
alternative for your client, but in order to reuse the water, it must
be recondensed, an energy intensive and complex system-and you still
need biocides as some of the volatile organics from the ink recondense
too and become a food source for bacteria. If biocide feed is all that
is needed, a small chemical metering pump can add it to the
wastewater. A proportional feed system can be set up if you want to
get real sophistocated (not really needed). Again, see the ink

I refer you without reservation to the following systems vendor who
can assist you with membrane treatment systems:

Mr. Tom Doherty

>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?

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