Chemical Oxygen Demand (COD)

Chemical symbol/abbreviations:

COD

Form commonly found in stormwater:

Residual food and beverage waste from cans/bottles, antifreeze, emulsified oils.

Solubility in water:

Most forms of COD are water soluble

Related constituents:

Biochemical oxygen demand (BOD) – a slightly more refined measure of water quality constituents than COD. BOD measures the amount of organic components that can be biologically degraded in water.  COD and BOD are measured in mg oxygen/L of water.  COD is always equal to or greater BOD.  The ratio of BOD to COD is the percent of the organic materials in water that can be degraded by natural micro-organisms in the environment.

Dissolved oxygen (DO) – a measure of oxygen dissolved in water.

Adverse human impacts:

High levels of COD in water often correlate with threats to human health including toxic algae blooms bacteria from organic wastes and seafood contamination.[ii]

Adverse impacts on the environment:

High COD levels decrease the amount of dissolved oxygen available for aquatic organisms.  Low (generally under 3 mg/L) dissolved oxygen, or “hypoxia,” causes reduced cell functioning, disrupts circulatory fluid balance in aquatic species and can result in death of individual organisms.[iii] as well as large “dead zones”.[iv]  Hypoxic water can also release pollutants stored in sediment.[v]

Stormwater Treatment to Remove COD and BOD

Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) in Stormwater FAQs

What is chemical oxygen demand (COD) and biochemical oxygen demand (BOD)?2019-07-24T16:28:10+00:00

Chemican oxygen demand (COD) and biochemical oxygen demand (BOD) – a slightly more refined measure of water quality constituents than COD – measures the amount of oxygen that would be required to fully break down the organic components that can be biologically degraded in water. COD and BOD are measured in mg oxygen/L of water. COD is always equal to or greater BOD. The ratio of BOD to COD is the percent of the organic materials in water that can be degraded by natural micro-organisms in the environment. Dissolved oxygen (DO) is a measure of oxygen dissolved in water.

What causes high COD/BOD in stormwater runoff?2019-07-24T16:28:22+00:00

High COD/BOD levels in stormwater runoff are cause by the residual food and beverage waste from cans/bottles, antifreeze, and emulsified oils from industrial food processing and agricultural activities. As most forms of COD are water soluble, this pollutant spreads easily via stormwater to waterways.

Why should COD/BOD be reduced in industrial stormwater runoff?2019-07-24T16:28:35+00:00

COD / BOD should be removed from stormwater because high levels in waterways often correlate with threats to human and wildlife health through toxic algae blooms, and bacteria from organic wastes and seafood contamination. [ii]

High COD / BOD levels also decrease the amount of dissolved oxygen available for aquatic organisms. Low (generally under 3 mg/L) levels of dissolved oxygen, or “hypoxia,” causes reduced cell functioning, disrupts circulatory fluid balance in aquatic species and can result in death of individual organisms[iii], as well as large “dead zones” in the waterbody.[iv] Hypoxic water can also release pollutants stored in sediment.[v]

How is COD/BOD reduced in industrial stormwater runoff?2019-07-24T16:28:46+00:00

In most applications, chemical oxygen demand (COD) and biochemical oxygen demand (BOD) can be reduced using passive media filtration and/or polishing. StormwateRx offers enhanced and advanced stormwater treatment systems to remove COD. The Aquip passive media filter and the Purus polisher combined offer an advanced level of COD removal from stormwater prior to discharge to help facilities meet benchmarks or NALs. Learn more about our stormwater media filtration and polishing technologies. Save

Background:

Chemical oxygen demand (COD) is often used to measure organic matter in wastewater, treated effluent, and receiving waters. Although COD measures more than organic constituents, the organic fraction usually predominates and is the constituent of interest.[vii] Chemical oxygen demand was developed as an alternative to the more lengthy BOD analysis.

Sources of COD in stormwater are varied. However, soluble organic compounds are most likely to contribute to escalated COD concentrations. Residual food waste from bottles and cans, antifreeze, emulsified oils are all high in COD and are common sources of COD for industrial stormwater. A typical COD concentration for soda and beer is about 100,000 mg/L.

U.S. EPA recommended water quality criteria:

None. Dissolved oxygen water quality criteria depend upon natural stream temperature and dissolved oxygen level.[i]

Appendices

[i] U.S. EPA, National Recommended Water Quality Criteria, http://www.epa.gov/waterscience/criteria/wqctable/index.html#U (last visited July 7, 2010).

[ii] See National Science & Tech. Council, An Assessment of Coastal Hypoxia and Eutrophication in U.S. Waters, 2 (2003) available at http://oceanservice.noaa.gov/outreach/pdfs/coastalhypoxia.pdf.

[iii] Ambient Aquatic Life Water Quality Criteria for Dissolved Oxygen (Saltwater): Cape Cod to Cape Hatteras, 65 Fed. Reg. 71317, 71318 (Nov. 30, 2000).

[iv] Ecological Society of America, Hypoxia http://www.esa.org/education_diversity/pdfDocs/hypoxia.pdf (last visited Aug. 11, 2010).

[v] Ecological Society of America, supra.

[vi] Standard Methods, 5-14(Andrew Eaton, et al. eds., 21st ed. 2005).

Aquip® industrial stormwater filtration system uses an innovative enhanced media filtration process to effectively remove soluble and insoluble aluminum and other metals as well as oils, suspended solids, organics and nutrients from industrial stormwater runoff.

Purus® Stormwater Polishing System provides the most advanced level of stormwater treatment, and is designed for challenging stormwater conditions or targeted polluant removal.

2019-07-26T10:06:04+00:00