Oxygen dynamics and heterotrophic aspects of a pond treatment system for cattle feedlot effluent

Abstract

The oxygen dynamics and heterotrophic activities of a waste treatment system, consisting of a storage pond, a high rate algal pond (HRAP) and a fish pond, which handles the effluent from a cattle feedlot are presented. Long-term and short-term observations suggest that BOD loading rates of 9·5 to 35 gm −2 day −1 can be used in the HRAP, depending on the season. The wastewater had a high COD to BOD ratio and the ratio decreased through the system. It is hypothesized that the eventual biodegradation of compounds initially measured in COD, but not BOD, estimates must pass through a stage in which it contributes to BOD estimates, thereby contributing to the observed COD : BOD ratios. Aerobic and anaerobic bacteria were present in high numbers in the storage pond and HRAP and contributed to heterotrophic activity and waste stabilisation. A significant (>99·6%) overall reduction in bacterial numbers was achieved in the system.