Respirometry as a Tool for Troubleshooting of Biological Wastewater

EBS often uses respirometry as a valuable tool when evaluating client wastewater treatment systems and programs. It is a versatile instrument that allows us to conduct studies aimed at evaluating and optimizing treatment plant performance and can also be used to evaluate the potential impact of new chemicals entering the wastewater treatment plant. Respirometry testing is an ideal technique for evaluating chemical and biological additives in biological wastewater treatment systems and for measuring the kinetics of wastewater treatment, oxygen utilization rates, the impact of toxic shock events and process control. The following information provides insight into respirometry.

What is respirometry?

Respirometry is a general term encompassing a number of techniques for obtaining estimates on the rates of metabolism of vertebrates, invertebrates, plants, tissues, cells, or microorganisms. In wastewater microbiology, we use it to determine the viability of bacteria via direct or indirect measurement of oxygen consumption.

So how is oxygen consumption measured?

If bacteria are alive, they consume oxygen. One method for measuring oxygen consumption is manually via the DOUR/SOUR test. Computer-controlled respirometers can be used for more advanced measurement.

Manual Oxygen Uptake Testing via DOUR/SOUR

The Dissolved Oxygen Uptake Rate (DOUR) measures the respiration rate of microorganisms. It is the calculation of oxygen uptake (how quickly the microbes are using the oxygen). The Specific Oxygen Uptake Rate (SOUR) is defined as the milligram of oxygen consumed per gram of volatile suspended solids (VSS) per hour. SOUR is the relationship between oxygen uptake and the amount of solids.

BOD Bottle and DO Meter

DOUR/SOUR is used for:

• Daily performance monitoring

• Identifying toxicity

• Determining viability of lightly loaded systems

• Balancing loading and flows in parallel basins

• Monitoring recovery from upsets

DOUR/SOUR can be used as a real time monitoring approach to improve process operation and troubleshoot a variety of treatment issues.

Bench Respirometers

Computer-controlled respirometers can be used for more advanced BOD testing, biodegradability assessments, bioremediation testing and toxicity screening studies. These instruments continuously and precisely resupply oxygen to sealed reactors needed to sustain bio-reactions in liquids or semi-solids over extended periods of time. Two bench respirometers that EBS utilize are the Challenge Respirometer and the Surcis Respirometer.

The CHALLENGE Respirometer System facilitates an automated, precision measured, and continuous recording of respiration rates on up to 24 reactors simultaneously for both aerobic and anaerobic lab-scale cultures. This system can be operated in the aerobic mode in which oxygen uptake is measured or in anaerobic mode in which the production of biological gases is measured.

Challenge AER200






The BM Respirometry System by Surcis S.L employs a reaction vessel that can replicate the actions occurring in a treatment plant and assess the process through fundamental measurements such as the speed the process consumes oxygen, short term biological oxygen demand, biodegradable fractions of COD, non-biodegradable fractions of COD, specific toxicity for a determined activated sludge process, nitrification activity, and others. Surcis BM respirometry analyzers demonstrate results in a quick and practical manner by utilizing the actual activated sludge from the aeration tank. In addition, it provides a treatment plant operator with essential information to help protect and control the biological process of the plant.

Surcis BM Advance Respirometer









Although new to the industry, the Surcis BM Respirometry System shows promise with regard to the type of valuable data it provides during the troubleshooting phase. The Surcis respirometer is now being distributed in the United States by Environmental Business Specialist. For more information, please contact EBS.