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:
Adverse impacts on the environment:
Treatment to Remove COD and BOD
Explore solutions for managing BOD/COD in stormwater and wastewater with our partner company, Aeration Industries.
Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) in Stormwater FAQs
Chemical 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.
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.
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]
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:
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.