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Research Project: Development of Technologies and Strategies for Sustainable Crop Production in Containerized and Protected Horticulture Systems

Location: Application Technology Research

Title: Granular activated carbon to remove agrichemicals from water

Author
item Fisher, Paul - University Of Florida
item Grant, George - University Of Florida
item Zayas, Victor - University Of Florida
item Raudales, Rosa - University Of Connecticut
item Altland, James
item Boldt, Jennifer

Submitted to: Greenhouse Grower Magazine
Publication Type: Trade Journal
Publication Acceptance Date: 4/16/2016
Publication Date: 4/26/2016
Citation: Fisher, P., Grant, G., Zayas, V., Raudales, R., Altland, J.E., Boldt, J.K. 2016. Granular activated carbon to remove agrichemicals from water. Greenhouse Grower Magazine. May/June: 20-22.

Interpretive Summary: Many growers capture and reuse irrigation water in ponds or flood irrigation tanks. Agrichemical residues can potentially build up over time and affect future crops irrigated with residue-laden water. One key chemical of concern is paclobutrazol, which is very persistent, with a half-life of around six months in water. Although paclobutrazol is usually applied in the parts per million (ppm) range, research by the University of Florida (UF) in the 1990s showed that irrigating with levels as low as 5 parts per billion (5 ppb) of paclobutrazol can seriously impact growth of sensitive crops. Begonia is an excellent candidate to be our canary in the coal mine. Plants are severely stunted when continuously irrigated with water containing 5 ppb of paclobutrazol. Our research team at UF, USDA-ARS, and University of Connecticut measured paclobutrazol in runoff collected in catchment ponds or tanks during periods of spring chemical use and 76% of samples were above the 5 ppb biologically-active level. An effective method to remove paclobutrazol and other agrichemicals is granular activated carbon (GAC). A GAC filter is essentially a rapid sand filter filled with GAC rather than sand or glass. Agrichemicals become adsorbed to carbon particles as irrigation water passes through the filter. Initial results found over 95% removal of a 50 ppb paclobutrazol solution. Grower results using GAC at a commercial scale have been excellent. We also found that ozone removed more than half of the paclobutrazol from return water at a grower installation. GAC technology is low cost relative to most other water treatments, simple to use, and highly effective. Further research will refine management guidelines for GAC use. We are excited about the potential impact of this technology to help growers successfully recycle irrigation water.

Technical Abstract: Many growers capture and reuse irrigation water in ponds or flood irrigation tanks. Agrichemical residues can potentially build up over time and affect future crops irrigated with residue-laden water. One key chemical of concern is paclobutrazol, which is very persistent, with a half-life of around six months in water. Although paclobutrazol is usually applied in the parts per million (ppm) range, research by the University of Florida (UF) in the 1990s showed that irrigating with levels as low as 5 parts per billion (5 ppb) of paclobutrazol can seriously impact growth of sensitive crops. Begonia is an excellent candidate to be our canary in the coal mine. Plants are severely stunted when continuously irrigated with water containing 5 ppb of paclobutrazol. Our research team at UF, USDA-ARS, and University of Connecticut measured paclobutrazol in runoff collected in catchment ponds or tanks during periods of spring chemical use and 76% of samples were above the 5 ppb biologically-active level. An effective method to remove paclobutrazol and other agrichemicals is granular activated carbon (GAC). A GAC filter is essentially a rapid sand filter filled with GAC rather than sand or glass. Agrichemicals become adsorbed to carbon particles as irrigation water passes through the filter. Initial results found over 95% removal of a 50 ppb paclobutrazol solution. Grower results using GAC at a commercial scale have been excellent. We also found that ozone removed more than half of the paclobutrazol from return water at a grower installation. GAC technology is low cost relative to most other water treatments, simple to use, and highly effective. Further research will refine management guidelines for GAC use. We are excited about the potential impact of this technology to help growers successfully recycle irrigation water.