49    USE OF RESPIROMETRY TO EVALUATE THE
EFFICACY OF BIOLOGICAL PRODUCTS FOR THE
BIODEGRADATION OF WASTEWATER GREASE AND OIL
J. L Tisinger, Senior Research Engineer
D. J. Drahos. Senior Research Scientist
Sybron Chemicals, Inc.
Salem, Virginia 24153
INTRODUCTION
A laboratory screening protocol was developed to test the efficacy of commercial bacterial
products for enhancing the biodegradation of wastewater grease and oil. Biological products formulated with several species of commercially grown bacteria were used to evaluate the
biodegradability of waste grease and oil obtained from industrial wastewater treatment systems,
municipal lift stations and restaurant grease traps.
A biological product is a combination of several natural, environmental bacterial isolates commercially grown and formulated with chemical components to enhance the biodegradation of recalcitrant compounds. The process of adding commercial bacteria to increase the degradability
of target compounds is called bioaugmentation. The commercial cultures consist of bacteria selectively enhanced and enriched to provide a superior rate of degradation of grease. The chemical components consist of macro and micro nutrients, pH buffers, enzymes, growth inducers, stabilizers and low concentrations of biodegradable surfactants. The two biological products used in
this study contained both vegetative and sporulated species. Both gram-negative and gram-positive species were tested.
In order to test many samples economically, respirometry was chosen to provide a quick, inexpensive, and reproducible method for measuring grease biodegradability. Our overall project
goal was to determine the potential of our biological products compared to the indigenous bacteria for the biodegradation of the field-collected grease samples. The findings of this study
showed that the biological products significantly improved the biodegradability of the waste
grease compared to the indigenous micro flora.
BACKGROUND
Oil and Grease (O&G) are found in many wastewater collection and treatment systems. Grease
traps are required for the protection of the down stream pipes and treatment system from O&G
which builds up on pipes and may contribute to filamentous bacterial growth.' Some problems
that occur are plugging, odors, foaming, and costs associated with removal and disposal of solid
waste. The reduction in pump out times and the elimination of odors were stated as the goals by
the business owners for bioaugmentation. Immediately after pumping, as well as in clean restaurant grease traps, the liquid surface in the trap is open to the atmosphere. Dissolved oxygen in
grease traps can exist from the entrainment of air in the incoming wastewater and from the liquid
surface exposure. A well maintained bacterial population may reduce the grease cap layer, thus
allowing more oxygen to enter from the atmosphere.
It was reported that the oil and grease found in many restaurant grease traps and municipal
waste facilities is mainly animal and vegetable fats. The fats in a typical grease trap are nonpolar triglycerides which are usually broken down to their fatty acids and glycerol components.
However, animal and vegetable greases contain high levels of long chain fatty acids (C14-C18)
51st Purdue Industrial Waste Conference Proceedings. 1996. Ann Arbor Press. Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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