Section 18. BIOLOGICAL SYSTEMS
SHOCK LOAD CAPABILITIES OF ANAEROBIC SYSTEMS
TREATING HIGH STRENGTH WASTEWATERS
Enos L. Stover, Professor
Reinaldo Gonzalez, Graduate Student
Bioenvironmental and Water Resources Engineering
School of Civil Engineering
Oklahoma State University
Stillwater, Oklahoma 74078
Ganapathi Gomathinayagam, Environmental Engineer
IMS Engineers
Rochester, New York
INTRODUCTION
Biological treatment of high strength industrial wastewaters by aerobic treatment methods has
often been limited by the variable nature of the wastewater, economics of treatment, excessive sludge
production, and physical limitations relative to adequate oxygen transfer and solids settling and thickening problems. On the other hand, anaerobic treatment of high strength wastewaters can be highly
feasible while not being limited by these problems. With many types of wastes, high treatment efficiencies can be achieved by anaerobic treatment along with low sludge production and production
of enough methane to make the treatment facilities self-sufficient from an energy standpoint.
The key to maintaining process control and stable operations in biological treatment systems
(aerobic or anaerobic) is to provide proper environmental conditions to the biomass or bacteria in
the system. Changing environmental conditions, especially fluctuations in wastewater characteristics,
tend to disrupt steady-state conditions which the biological treatment facilities were designed to approach. The hydraulic flow rate and organic (BOD or COD) loading rate, along with the variability
in these parameters, are two of the most critical parameters relative to maintaining stable operating
conditions; of course, pH, temperature, nutrients, and lack of toxic or inhibitory substances are also
critical to successful operations. Environmental changes tending to disrupt steady-state conditions
(shock loads) which cannot be, or have not been, smoothed by preventive engineering measures must
be accommodated solely by successful biological response or by combined biological and operational
remedial responses.
Due to the previously described advantages of anaerobic treatment of high strength wastes, an
extensive research program was undertaken with both fixed-film and suspended growth anaerobic
systems to evaluate their response capabilities under both shock load conditions and total feed shutdown periods. During production or manufacturing processes, wastewater discharge characteristics
may vary significantly both in quantity and quality or temporarily ceased for clean-up operations,
mechanical breakdown of equipment or overhauling of production facilities. Some facilities, especially food processing plants may have significant variations in wastewater discharges on a seasonal
basis. There may also be significant periods of time where no wastewaters are generated. With these
wastewater discharge characteristics in mind, the capabilities of anaerobic treatment systems to handle shock loads relative to changes in flow, organic loading rates, temperature, pH, nutrients, and
shutdown or no feeding periods were investigated. The results from these experiments are discussed
here to show the stability and response capabilities of these systems relative to substrate removal,
effluent quality, gas production, and gas quality under changing conditions.
MATERIALS AND METHODS
Bench-scale complete-mix, continuous flow anaerobic suspended growth (activated sludge) systems were used in these studies. The wastewaters were pumped to the mix tank reactors, and the
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