63    HEAVY METALS REDUCTION PRETREATMENT
DESIGN AND PLANNING FOR SPACE OPTIMIZATION
USING THE HYDROXIDE METHOD
Mohamad B. Ismail, Environmental Engineer
Woolpert
Dayton, Ohio 45402
INTRODUCTION
Woolpert was hired by an automotive manufacturer to provide engineering services for designing a pretreatment plant to treat wastewater from a newly installed paint system. The manufacturer had the integrated expertise in the development and production of vehicle chassis components and subsystems, including suspension, braking, traction to the wheels, and electronic
integration. The new paint system was expected to discharge high concentrations of certain metals including chromium, lead, and zinc. The metal concentrations were expected to be discharged
to the city sanitary sewer collection system at levels higher than permitted. As a result, a new
pretreatment plant was required.
DESIGN PARAMETERS
In preparing the design for the pretreatment plant, several factors were considered. The focus
of concern was influent and effluent characteristics, as well as space and height limits for installing all necessary equipment to provide a complete pretreatment plant.
INFLUENT AND EFFLUENT CHARACTERISTICS
The new paint system that will discharge wastewater with high concentrations in chromium,
lead, and zinc was one of the first systems of this type to be installed in the country. Figure 1 is a
process schematic of the paint system showing the system's major components. It consists
mainly of several tanks containing sodium hydroxide, phosphoric acid, zinc phosphate,
chromium seal, and deionizers. Flow from these tanks, as well as the rinse tanks, will overflow
to the proposed treatment plant.
As mentioned above, this system was one of the first systems to be installed in the country,
and as such, no current effluent data were available. Therefore, the proposed effluent characteristics had to be estimated. After discussions with the owner, the paint system manufacturer, and
the chemical supplier, the paint effluent wastewater or pretreatment plant influent characteristics
were determined and are presented in Table I.
Most municipalities that operate a publicly owned treatment works (POTW) have a pretreatment program that regulates the effluent from major industries that discharge wastewater to their
sanitary sewer system. The pretreatment program has effluent limits that meet or exceed the limits defined in 40 CFR (Code of Federal Regulations) Part 433. On May 30, 1995, the United
States Environmental Protection Agency (USEPA) proposed new limits for the metal products
and machinery (MP&M) industry (40 CFR Part 438) which should supersede 40 CFR Part 433.
Since the new limits were not finalized and are still in debate, these new limits were not used. Instead, the current effluent limits were used. Table II presents the allowable effluent limits for the
wastewater pretreatment plant.
51st Purdue Industrial Waste Conference Proceedings, 1996, Ann Arbor Press. Inc.. Chelsea. Michigan 48118
Printed in U.S.A.
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