RECLAIMING PLATING WASTEWATER BY REVERSE OSMOSIS
Jay E. Warlike, Manager
Kenneth G. Thomas, Process Engineer
Beckman Instruments, Inc.
Porteville, California 93257
Samuel C. Creason, Principal Application Engineer
Beckman Instruments, Inc.
Fullerton, California 92634
INTRODUCTION
The Porterville, California facility of Beckman Instruments, Inc., is responsible for producing printed circuit boards which are used in a wide variety of process and scientific
instruments.   About 10,000 sq ft of material is processed each month.  Copper, tin-lead
and gold plating are performed in a conventional subtractive process.
In 1973-74, plant water usage averaged about 1.5 million gal/month and was increasing.   A continuing increase soon would have become unacceptable, since rather extensive
modifications to the Porterville city water system would have been required.   Further, it
was felt that the reject rate of the plating operation could be significantly lowered by
improving the quality of the rinse waters.   Finally, the prospect of meeting EPA waste
discharge requirements had to be considered.   Accordingly, a program was undertaken to
assess the situation and implement a satisfactory solution.   The result is a system which
has reduced water consumption by about 70% and lowered the cost of shop rejects to
less than a third of its previous value.   It complies fully with the 1983 goal of zero
discharge.
WATER CONSERVATION
The overall problem was attacked in two ways.   First, to minimize water consumption,
rinse-tank controllers were installed on the plating line.   These are devices which sense
the conductivity of the water in a rinse tank and admit fresh water if the conductivity of
the water is above a prespecified value.   Manual control, which relies on an operator to
turn on water when parts are being rinsed and to shut off water flow to idle rinse tanks,
is thereby eliminated.   The usefulness of the controllers can hardly be overemphasized.
After their installation, water consumption decreased to 750,000 gal/month, about half
the previous value.
With water consumption reduced to a tolerable value, attention was turned to the
problems of improving the quality of the water and meeting effluent discharge
requirements.
WATER TREATMENT
There are two streams which feed the water treatment system:   Porterville city water
and contaminated rinse water.   A typical analysis of city water is shown in Table I.   In
this particular case, the conductivity is shown as 290 /imhos, but it may range as high as
400.   The conductivity of the contaminated rinse water may range as high as 1000 jumhos.
Reverse osmosis was chosen as the principal method for water purification.   A solar evaporation pond was selected as the means to deal with wastes which could not be recycled
through the reverse osmosis system.
Overview
A block diagram of the water treatment scheme is shown in Figure 1.   Wastewater
from the plating shop is segregated into two streams.   About 2000 to 3000 gpd is sent
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