Oxygen Demand-An Alternative Method for Testing Oxygen Demand
in a Sewage Treatment Facility
University of Montana
In 1986 the Missoula Wastewater Treatment Facility requested a permit change
from the biological oxygen demand (BOD) test to the carbonaceous biological
oxygen demand (CBOD) test. The permit change request is based on an EP A
evaluation which stated that BOD may not be a suitable test because the
nitrogenous oxygen demand is expressed in the effluent but not in the influent
testing. However, nitrogenous oxygen demand is ignored in the CBOD test and
nitrogen loading could be allowed to increase if no limits are placed on
nitrogen loading. The Clark Fork already has a problem with algae and an
increase in ammonia may increase the secondary oxygen demand reducing the water
quality in this section of the Clark Fork River.
The ultimate oxygen demand (UOD) is proposed as a better means of assessing the percent removal of both the carbonaceous and nitrogenous oxygen dem3lld in the effluent. The UOD can be easily calculated for both the influent and effluent waters using the amount of org3ltic carbon and nitrogen in the wastewater.