1920x420 Biochemical Oxygen Demand

BOD Analyzers, Test Kits

Why Test BOD?

Biochemical oxygen demand, otherwise known as biological oxygen demand, is an important parameter in water treatment. When effluent wastewaters are discharged into the environment, they can introduce pollution in the form of organic content to receiving waters. High concentrations of organics can deplete dissolved oxygen levels in water, leading to negative environmental and regulatory consequences.

To help determine the impact and ultimately limit the amount of organic pollution in water, BOD is an essential measurement. USEPA also allows the use of total organic carbon (TOC) when it is correlated with BOD or COD.

At Hach®, find the BOD analyzers, testing equipment, resources, training and software you need to successfully monitor BOD in your specific process application.

Featured BOD Product Categories

Online BOD Analyzers

Biotector 3500c

Complete online solutions for your BOD analysis needs.

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Benchtop BOD Analyzers

HQD Benchtop Meter Kit

Benchtop instruments can provide fast, accurate BOD measurements when quick results are needed.

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Sensors and Electrodes

IntelliCAL LBOD101

The Hach IntelliCAL LBOD101 optical dissolved oxygen probe improves confidence in the BOD5 testing procedure.

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Which Processes Require BOD Monitoring?

Influent waters entering wastewater plants are high in organics and the wastewater plant must reduce the "organic loading" before discharging water back into a receiving body.

Oxygen demand is useful for measuring waste loadings, evaluating the efficiency of the treatment processes, and ensuring effluent compliance.

  • Primary Treatment

    Clarifiers, or sedimentation basins, slow the flow of the wastewater to allow suspended solids to settle. Surface skimmers collect any floating fats, oils and greases. With the use of this mechanical and physical means, approximately 30% of organic matter is removed from the wastewater and is routed to the solids management area of the plant. Clarifiers, or sedimentation basins, slow the flow of the wastewater to allow suspended solids to settle. Surface skimmers collect any floating fats, oils and greases. With the use of this mechanical and physical means, approximately 30% of organic matter is removed from the wastewater and is routed to the solids management area of the plant. By monitoring BOD in the primary treatment, the wastewater facility can control the efficiency of this process.

  • Secondary Treatment

    This process uses living organisms to aid in reducing organics. In the aeration basin, bacteria and microorganisms convert biodegradable organic matter to carbon dioxide and water. With this conversion, organics are reduced, therefore reducing oxygen demand.

  • Discharge Limits

    Discharge limits vary from plant to plant depending on the characteristics of the receiving water, effects on aquatic life, recreational uses and other factors. Discharge permits may stipulate a specific maximum effluent concentration for BOD or COD, pounds loading, and/or a percent removal.

For compliance, it’s necessary to measure BOD or COD of the influent water as it enters the plant, before mechanical screening processes, and at the effluent of the facility at the designated discharge sample location. If the oxygen demand of effluent exceeds discharge limits, regulatory agencies may impose fines. USEPA also allows the use of TOC when it is correlated with BOD or COD.


When selecting a method for analyzing oxygen demand, it’s important to consider the following:

  • Specific testing application
  • Oxidant that will be used
  • Test completion time
  • Accuracy and precision of the measurement
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Aeration basins aid in reducing organics that enter the treatment plant from influent waters. Biodegradable organic matter is converted into carbon dioxide and water

How is BOD Measured?

Dilution Method

Winkler Titration

Respirometric or Manometric Method

BODTrak II Respirometric BOD Apparatus
2952400
$5,283.00

BOD Testing Limitations:

Frequently Asked Questions

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