71    ZERO SLUDGE/ZERO DISCHARGE PRETREATMENT
SYSTEMS FOR THE METAL FINISHING AND PLATING
INDUSTRY
Mark W. Davis, Process Engineer
Tom Sandy, Process Engineer
CH2M HILL
Bellevue, Washington 98005
INTRODUCTION
A wide variety of metals are used in the metal finishing and plating industry. Although some of
these metals are relatively benign, most are toxic to either humans or wildlife.
Many metal finishing and plating companies discharge their wastewater to municipal sewage treatment plants. Because metal contaminants accumulate in the sludge produced by conventional wastewater treatment systems, thus complicating disposal, pretreatment of the wastewater is required. The
Environmental Protection Agency's (EPA) pretreatment standards for heavy metals and cyanide for
the electroplating and metal finishing categories are presented in Table I. Because state and local
governments may have stricter standards than those shown, it is important to identify all pertinent
regulatory standards before designing a treatment system.
Table I.    Pretreatment Standards for the Electroplating and Metal Finishing Subcategories'
Electroplating Effluent Guidelines (mg/L) Pretreatment Standard - Existing Source (PSES)
Averages of Daily
Maximum Values for (4)
for any Consecutive Monitoring
Pollutant Any 1 Day Days Shall Not Exceed
Cyanide, total" 1.9 1.0
Copper 4.5 2.7
Nickel 4.1 2.6
Chrome, total 7.0 4.0
Zinc 4.2 2.6
Lead 0.6 0.4
Cadmium 1.2 0.7
Total metals 10.5 6.8
Metal Finishing Subcategory (PSES) Pretreatment Standards —Existing Sources (mg/L)
for any Monthly Average
Pollutant Any 1 Day Shall Not Exceed
Cadmium (T) 0.69 0.26
Chromium (T) 2.77 1.71
Copper (T) 3.38 2.07
Lead (G) 0.69 0.43
Nickel (T) 3.98 2.38
Silver (T) 0.43 0.24
Zinc(T) 2.61 1.48
Cyanide (T) 1.20 0.65
Cyanide, amenable 0.86 0.32
a For less than 10,000 GPD effluent, the cyanide limits are 5.0 mg/L (max day) and 2.7 mg/L
(4-day average). Also, lead and cadmium are the only restricted metals.
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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