BIOCHEMICAL OXYGEN DEMAND (BOD)

Biochemical Oxygen Demand or Biological Oxygen Demand, is a measurement of the amount of dissolved oxygen (DO) that is used by aerobic microorganisms when decomposing organic matter in water. BOD can be measured in rapidly or real-time with Real Tech’s instruments to improve wastewater process control and plant efficiency.

HOW TO MEASURE BOD IN REAL-TIME

To measure BOD rapidly or in real-time, Real Tech’s innovative BOD/COD meter and  BOD/COD sensors utilize patent-pending and proprietary technologies to provide superior measurement performance across multiple wavelengths of light using UV LEDs.

Many compounds absorb light in the UV-VIS spectrum including organic compounds. The instruments measure organics in a multi-dimensional way that results in improved correlations to aggregate organics water quality parameters, such as BOD and COD. This also allows the sensors to be able to detect changes in the composition of organics independently of their concentration.

To ensure the results are as accurate and predictive of the lab as possible, Real Tech’s Liquid Ai^® platform suite of services can be used in combination with our BOD/COD instruments

For rapid testing with our BOD/COD meter, the Liquid Ai^® Data Management PC software empowers users to create their own custom calibrations to capture site-specific water conditions in addition to various other sample and calibration management abilities.

For continuous, real-time monitoring with our BOD/COD sensors, the Liquid Ai^® data analytics services provide ongoing calibration health monitoring. The service enables continuous calibration improvements to be made as water quality composition changes or new contaminants are introduced. We ensure reliability and trust in the results, so our clients can make confident, informed decisions to improve their plants processes. The longer our systems are installed, the smarter and more insightful they become with our Liquid Ai^® services.

IMPORTANCE FOR WASTEWATER

Biochemical oxygen demand / biological oxygen demand is an important water quality parameter because it provides an index to assess the effect discharged wastewater will have on the receiving environment.

The higher the BOD value, the greater the amount of organic matter or “food” available for oxygen consuming bacteria. If the rate of DO consumption by bacteria exceeds the supply of DO from aquatic plants, algae photosynthesis or diffusing from air, unfavourable conditions occur. Depletion of DO causes stress on aquatic organisms, making the environment unsuitable for life. Further, dramatic depletion can lead to hypoxia or anoxic environments.

BOD is also used extensively for wastewater treatment, as decomposition of organic waste by microorganisms is commonly used for treatment. Regulations and permitting for biochemical oxygen demand effluent will vary by country and region, such as the National Pollution Discharge Elimination System (NPDES) in the United States, with a maximum allowable concentration established for either direct discharge to the environment or discharge to a municipal sewer system.

BENEFICIAL APPLICATIONS FOR MONITORING

Real-time or rapid BOD monitoring is becoming increasingly popular, and it’s no surprise as the alternative is a 5-7 day wait for lab results.

Continuous organics monitoring opens the door for many new treatment process control and optimization possibilities that can result in significant cost savings, improved water quality, and compliance peace of mind.

Wastewater applications for online BOD measurement include:

LABORATORY DELAY FOR BOD RESULTS LIMITS ACTION

The most common laboratory method for determination of biological oxygen demand / biochemical oxygen demand is Standard Methods 5210B. A sample is first analyzed and conditioned to ensure favourable growth conditions for bacteria, which may include adjustment for pH, neutralization of residual chlorine, and/or reduction of DO in supersaturated samples. The sample is then diluted and the appropriate amount of seed bacteria added. The initial dissolved oxygen content is recorded and the sample is then incubated for 5 days at 20°C.

After the 5 day period, the sample is removed from the incubator and the final dissolved oxygen reading is taken. BOD is calculated from the DO depletion and volume of sample used following the formula below:

BOD₅ = BOD mg/L = [(IDO -DO₅) – seed correction] x dilution factor

Relying on grab samples leads to significant delays. When BOD results are received 5-7 days later, the information is usually of little value for process control and improving plant performance.

Plants need a practical and affordable solutions that deliver continuous information on wastewater composition and quality to operations personnel. Real Tech has the solutions to help our clients get the information they need, when they need it.