89    INDUSTRIAL LAUNDRY PRETREATMENT PLANT
DESIGN AND IMPLEMENTATION:
MUCH MORE THAN A TECHNICAL PROBLEM
Carol L. La Breche, Senior Project Leader
Roy F. Weston, Inc.
Houston, Texas 77056
Jack V. Matson, Associate Professor
University of Houston
Houston, TX 77204-4791
INTRODUCTION
This paper presents a case history involving the largest industrial laundry in Houston, Texas, and
concerns efforts to design, construct, and permit a wastewater pretreatment system that meets the
City of Houston's pretreatment standards for oil/grease, lead, zinc and pH. The initial system design
consisted of a solids removal system and a batch reactor for biological treatment. That was'the easy
part. Due to prior conflicts between the city and the facility, the city attempted to shut down laundry
operations prior to implementation. The same city officials also had to approve the design. Furthermore, the laundry increased its wastewater flow almost threefold by adding stone-washing of blue-
jeans during construction of the pretreatment system. The contractor walked off the job during a
contractual dispute at the 80% completion point. Finally, the city sewer system was found to be
inadequate once the plant was started up. Many of these problems called for drastic revisions of the
pretreatment system while it was under construction. Our interface between actual design and construction, and the realities of political, legal, and technical problems is this paper's subject.
BACKGROUND
In early April of 1986, the laundry's owner came to the University of Houston for help in what he
called a final, desperate attempt to keep his business running. He was holding a 2-year Interim
Industrial Waste Permit that allowed his company to discharge wastewater to the city sewer. The
Interim Permit was due to expire in only seven months. Time was of the essence.
During the months of May and June, the laundry facilities were evaluated. Operating on an
intermittent basis, 8 to 10 hours per day, the laundry generated 300 gallons per minute of wastewater.
The laundry washed uniforms, lab coats, floor mops, mats, and shop towels from small businesses
and industries throughout the Houston area. The wastewater produced was of a complex and variable
nature, making it difficult to characterize. Wastewater analyses (Table I) verified that laundry effluent was above the City's maximum allowable limits for oil/grease, lead, zinc and pH. Organics
(measured by biochemical oxygen demand, BOD) and total suspended solids (TSS) (Table I) were also
high enough so that the laundry was assessed a sizable monthly surcharge on its utility bill. The
surcharge limits were 325 mg/L and 365 mg/L (Table I), above which additional fees were imposed on
dischargers. One concise problem statement was written: "How to design a pretreatment system to
remove lead, zinc, oil/grease, TSS, and BOD, and to adjust pH."
ENGINEERING THE CONCEPTUAL DESIGN
Our first recommendation, to conduct a pilot-scale air flotation system at the laundry, was rejected
by the owner. According to the laundry's owner, previously piloted models of filtration and air
flotation systems operated by other consultants on wastewater at the site ended in failure. Biological
treatment, our second right answer, was selected and a pilot test of a Rotating Biological Contactor
(RBC) was begun. The RBC is a fixed film process in which biological growths attach to shaft-
mounted discs that rotate slowly through a vat containing wastewater. Oxygen is supplied during
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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