87    COMBINING BIOLOGICAL AND PHYSICAL PROCESSES
FOR COMPLETE TREATMENT OF OILY
WASTEWATERS
Paul M. Sutton, Principal
P.M. Sutton & Associates, Inc.
Bethel, Connecticut 06801
Prakash N. Mishra, Staff Engineer
General Motors Technical Center
Warren, Michigan 48090
Paul M. Crawford, Manager
ZENON Environmental, Inc.
Burlington, Ontario, Canada
INTRODUCTION
General Motors (GM) has installed add-on biological treatment to conventional oily wastewater
treatment systems at a number of their manufacturing plant sites to achieve compliance with effluent
discharge regulations. The GM Delco Moraine New Departure Hyatt (NDH) plant in Sandusky, Ohio
is typical of these multi-stage physical-chemical and biological treatment facilities (Figure 1).
Although the plants have generally met design expectations, they are costly to install and operate,
mechanically complex and result in the generation of a significant quantity of chemical and biological
solids.
During the 1970s a novel wastewater treatment system was developed consisting of a suspended
growth biological reactor combined with a membrane ultrafiltration unit process (Figure 2).* The
ultrafiltration step provides a positive means of liquid-solid separation preventing any loss of biological solids into the effluent and therefore, allowing maintenance of a very high concentration of
biomass in the suspended growth reactor. The membrane biological reactor (MBR) system is most
attractive when applied in situations where long solids retention times (SRTs) are required, and
physical retention and subsequent hydrolysis are critical to achieving biological degradation of a
pollutant (e.g., biological treatment of an oily wastewater). The ultrafiltration unit in the system
PROCESS WASTEWATER
PLUS BACKWASH/FILTRATE
FROM SOLIDS
REMOVAL/DEWATERING
EXCESS BIOMASS
TO DIGESTER
EQUALIZATION
». SKIM OIL TO
RECLAMATION
OXYGENATION
EFFLUENT TO
POLISHING   "^
POND
tss
SOLIDS DEWATERING
AND THEN LANDFILL "*
SAND
FILTER
TWO-STAGE
FLUIDIZED BED
BIOLOGICAL TREATMENT
SAND
FILTER
DISSOLVED AIR
FLOATATION
FLOCCULATION
T-?
Figure 1.    Simplified process schematic of the current NDH industrial wastewater treatment plant.
•Further development of the technology to the application of oily wastewaters was done jointly by ZENON
Environmental, P.M. Sutton & Associates and General Motors. This process is patent pending and is being marketed
by ZENON under the trade name ZenoGem      system.
47th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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