TECHNICAL BULLETIN 135 General Oxygen Requirements for Wastewater Treatment
Oxygen requirements for municipal wastewater treatment can be predicted closely with the standard laboratory analysis using g the BOD test (special requirements exist for some industrial wastewater). The BOD test is designed to measure Biological Oxygen Demand for the wastewater and provides an excellent basis for design assuming:
For wastewater the field or actual oxygen demand is dependent on how far the treatment process is carried. In general the oxygen demand is broken into carbonaceous demands (oxygen required to stabilize carbon in the waste) and nitrogenous demand (oxygen required to stabilize nitrogen in the wastewater). Generally, nitrogen in the waste appears as ammonia (NH or NH4).
For many treatment plants the carbonaceous demand must be considered as 2 components:
For nitrogenous BOD the demand floor oxygen is 4.6 lb O2/ lb BOD (4.6 kg/kg) removed.. To achieve nitrogenous conversion of ammonia to nitrate requires longer aeration time with low food to microorganism ratio, i.e., much sludge MLS (M) with low food supply (F). This condition results in a long sludge age, which promotes s n nitrification.
Biological Nutrient Removal (BNR for Nitrogen)For advanced waste treatment systems denitrification may be required. To achieve denitrification both carbonaceous and nitrogenous removals must be successfully completed. Conversion of the nitrate (NO3) to nitrogen gas actually removes nitrogen from the system. A side result and benefit of denitrification is the recovery of oxygen and reduction of total oxygen requirements. Oxygen recovery is approximately 2.86 lb O2 per lb (kg/kg) of NO3 reduced and removed.
Total Oxygen Requirements
Field oxygen requirements for BOD D removal can be computed as:
Carbonaceous demand + Nitrogen demand Credit for oxygen recovered by denitrification
Each treatment process and each waste must be evaluated to determine field oxygen requirements.
At EDI Knowledge Center, you'll find invaluable resources and information from our engineers and industry leaders. The EDI Knowledge Center offers readers of our website a deeper exploration and understanding of the latest technologies, operator tips and developments in the wastewater industry. The Knowledge Center is available on the web and in your inbox.