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Iodinated Disinfection Byproducts found in Dairy-Impacted Wastewaters and Streams

Dairy cows in an animal feeding operation in New York
Wastewater from some dairy operations is discharged to wastewater treatment plants for treatment. Photo Credit: Brett Hayhurst, USGS.

Iodinated disinfection byproducts were found at stream locations downstream from treated discharge from wastewater treatment plants that receive dairy waste and in the wastewaters directly from dairy facilities.

Disinfection byproducts form when chlorine or other oxidizing agents react with organic matter in wastewaters. Because of the specific use of iodine and iodine-containing compounds in dairies, U.S. Geological Survey (USGS) scientists theorized that such operations, in conjunction with chlorine disinfection within the dairy processing facility or at municipal wastewater treatment plants (WWTPs) that receive dairy waste, could be a potential source of iodinated disinfection byproducts (iodo-DBPs) to corresponding receiving water bodies.

Iodo-DBPs were measured in wastewaters within dairy processing facilities (five milking and three cheese manufacturing) in New York and Wisconsin, and surface waters downstream from the discharge from two WWTPs that received dairy waste in California during 2014 and 2015.

Scientists determined that iodo-DBPs constituted 15−29 percent of the total DBPs measured in stream samples near WWTP effluents that were impacted by dairy waste. Iodo-DBPs constituted from 0 to 100 percent of the total DBPs in samples from dairy processing facilities. The fraction of iodo-DBPs was greater in dairy-impacted wastewaters than treated municipal wastewaters or oil and gas produced wastewaters that were sampled previously.

The results of this study identify the occurrence and potential pathways of iodo-DBPs to aquatic environments. Iodo-DBPs have been determined to be toxic to mammals; however, the effects on exposed aquatic biota remain poorly understood.

The study was supported by the USGS Toxic Substances Hydrology Program.


Hladik, M.L., Hubbard, L.E., Kolpin, D.W., and Focazio, M.J., 2016, Dairy-impacted wastewater is a source of iodinated disinfection byproducts in the environment: Environmental Science and Technology Letters, v. 3, no. 5, p. 190-193, doi:10.1021/acs.estlett.6b00109.

More Information

This article was featured as an article in the USGS GeoHealth Newsletter, Vol. 13, No. 1, 2016

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