BOD Loading Rates Research Articles

Rates of biogenic oxygen production in mass cultures of microalgae, absorption of atmospheric oxygen and oxygen availability for wastewater treatment

Oxygen for the aerobic treatment of wastewater in High Rate Algal Pond (HRAP) systems arises from biogenic production by microalgae during photosynthesis and from absorption of atmospheric oxygen through the air/water interphase. The total quantity of available oxygen per m 2 and day determines the permissible BOD loading rate of a HRAP. The quantity of biogenic oxygen production, has for the first time been measured in a closed bioreactor and open chemostatic cultures. Good agreement was obtained between the two methods where more than 1.92 g O 2 g(dry wt) was produced by the microalgae. This was significantly higher than oxygen yields calculated from a generalized compositional formula of algal biomass. In combination with a predictive mathematical model, it was possible to calculate the potential biogenic oxygen production per season for any latitude. This may serve as the basis of feasibility studies on application of HRAP systems.

Evaluation of Waste Stabilization Pond Performance in Missouri and Kansas, U.S.A.

Twenty waste stabilization ponds in Missouri and Kansas were evaluated as to their ability to meet the State effluent requirements. It was found that a large number of these ponds were violating the BOD or the suspended solids requirements on many occasions. The performance of these ponds did not correlate well with the traditional design parameters, such as BOD loading rates or mean hydraulic detention time. The use of multiple cells was also not found to be advantageous in all situations. Some of the pond design equations did not provide a valid method of estimating their performance. Effluent polishing methods are necessary to remove excess suspended solids during the critical summer months.

Factors Affecting Biological Removal of Phosphorus

A pilot plant study on biological removal of phosphorus was conducted over fifteen months to obtain optimum operational conditions and evaluate process performance. The pilot plant was composed of an anaerobic zone followed by an aerobic zone, and had a capacity of treating 100 m3 municipal wastewater per day. In the anaerobic zone, BOD loading rates and BOD to MLSS ratios were found to be important factors. In the aerobic zone, on the other hand, the hydraulic retention time had a significant influence on the phosphorus removal efficiency. For successful removal of phosphorus, a shorter hydraulic retention time in the aerobic zone along with appropriate parameters in the anaerobic zone (BOD loading rate ≦ 2 kg-BOD/kg-MLSS day, BOD to MLSS ratio ≦ 0.1 kg-BOD/kg-MLSS) are essential.

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

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.

A first-order kinetic model for designing anaerobic ponds in the treatment of palm oil mill effluent

Anaerobic ponds have been used as an initial step in the treatment of palm oil mill effluent (POME). Data on BOD loading rate and subsequent reduction exist but no systematic attempts have been made to synthesise these data into a theoretical framework for proper engineering design. This paper discusses alternative kinetic models for the design of ponding systems. First-order kinetic rate coefficients, k, are derived from the analysis of existing data from several sources. The average k value was found to be 0·36 day −1. With this theoretical model, derived from practical data, a simple approach can be used to arrive at an effective design. A case for further aerobic waste treatment following the anaerobic ponds is proposed.