| Summary: | Biodegradation of petroleum hydrocarbon can be an effective treatment method
applied to control oil pollution in both fresh water and marine environments.
Hydrocarbon degraders, both indigenous and exogenous, are responsible for utilizing
petroleum hydrocarbon as their substrate for growth and energy, thereby degrading
them. Biodegradation of hydrocarbons is often enhanced by bioaugmentation and
biostimulation depending on the contaminated environment and the competence of the
hydrocarbon degraders present. An evaluation of the performance of the biological
treatment of petroleum hydrocarbon by the hydrocarbon degrading microbes at the
Brayton Fire School??s 4 million gallon per day (MGD) wastewater treatment plant was
the main research objective. Samples were taken for two seasons, winter (Nov 03 ?? Jan
03) and summer (Jun 04 ?? Aug 04), from each of the four treatment units: the inlet tank,
equalization tank, aeration tank and the outfall tank. The population of aliphatic
hydrocarbon degraders were enumerated and nutrient availability in the system were
used to evaluate the effectiveness of on-going bioaugmentation and biostimulation.
Monitoring of general effluent parameters was conducted to evaluate the treatment
plant??s removal efficiency and to determine if effluent discharge was in compliance with
the TCEQ permit. The aeration tank is an activated sludge system with no recycling.
Hydrocarbon degraders are supplied at a constant rate with additional nutrient
supplement. There was a significant decrease in the population of microbes that was
originally fed to the system and the quantity resident in the aeration tank. Nutrient levels
in the aeration tank were insufficient for the concentration of hydrocarbon degraders,
even after the application of dog food as a biostimulant. The use of dog food is not
recommended as a nutrient supplement. Adding dog food increases the nitrogen and
phosphorus concentration in the aeration tank but the amount of carbon being added with
the dog food increases the total chemical oxygen demand (COD) and biochemical
oxygen demand (BOD). An increase in the concentration of total COD and BOD further
increases the nitrogen and phosphorus requirement in the system. The main objective of
supplying adequate nutrients to the hydrocarbon degraders would never be achieved as
there would be an additional demand of nutrients to degrade the added carbon source.
This research study was conducted to identify the drawbacks in the treatment plant
which needs further investigation to improve efficiency.
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