Respirometry, a Valuable Tool

EBS often uses respirometry as a valuable tool when evaluating client wastewater treatment systems and programs. Respirometers are versatile instruments that allow us to assess the treatability of a wastewater sample by measuring the respiration rate of aerobic or anaerobic microorganisms present in the wastewater. Respirometry can be used to evaluate and optimize wastewater treatment plant (WWTP) performance by analyzing the response of microbes to existing or new wastewater streams, process changes, toxic shock events, and the effects of chemical and biological additives. Additionally, they can be used for measuring the kinetics of wastewater treatment, such as oxygen and organic utilization rates.

What is respirometry?

Respirometry is a general term encompassing several techniques for obtaining estimates on the rates of metabolism of vertebrates, invertebrates, plants, tissues, cells, or microorganisms by measuring aerobic or anaerobic respiration. In wastewater microbiology, we use it to determine the activity of bacteria via direct or indirect measurement of oxygen consumption in aerobic processes or gas production in anaerobic processes. Since bacterial respiration is linked to the consumption of organics (BOD), monitoring it can provide an indirect measurement of the BOD removal rate and quantity.

How is respiration measured?

If bacteria are alive, they generally consume oxygen or produce gaseous byproducts, such as nitrogen gas or methane. One method for measuring oxygen consumption is done manually via the DOUR/SOUR test. Computer-controlled respirometers can be used for more advanced measurement of both aerobic and anaerobic respiration.

Respirometry

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 milligrams of oxygen consumed per gram of volatile suspended solids (VSS) per hour. SOUR is the relationship between oxygen uptake and the amount of solids.

DOUR/SOUR is used for:

  • Daily performance monitoring
  • Identifying toxicity
  • Determining viability of lightly loaded systems
  • 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 assessments such as toxicity screenings, BOD testing, standard biodegradability assessments, bioremediation testing, nitrification assessments, nutrient optimization, bioaugmentation evaluations, temperature evaluations, and chemical oxygen demand (COD) fractionation.

EBS utilizes the Respirometer Systems and Applications (RSA) PF-8000 model Respirometer, which facilitates an automated, precision measured, and continuous recording of respiration rates on up to 48 reactors simultaneously, for lab-scale cultures. This system can be operated in the aerobic mode or anaerobic mode. For aerobic processes, these instruments continuously and precisely resupply pure oxygen to sealed reactors needed to sustain bio-reactions in liquids or semi-solids over extended periods, while for anaerobic processes, the production of biological gases is measured.

For more information on respirometry and how your plant can take advantage of this tool to optimize your wastewater treatment plant, please call EBS at 985-674-0660 or contact us.

 

Learn about the microorganisms in your wastewater treatment system.