Bridging the GAPs: Approaches to Treating Water On Farms

Critical Selection and Evaluation Criteria of Treatment Methods

While various treatment methods exist, ultimately, the grower has to make a decision as to the technology that is best for their operation. The following list includes several factors and questions to consider when evaluating disinfection technologies.

Disinfection Volume: The volume of irrigation water as well as flow rate will be important in validating the system is actually effective in lowering the microbial load. Factors to consider include:

• Irrigation volume: Does the irrigation system apply acre-inches or acre-feet of water? Two inches per week over 10 acres is 543,000 gallons per week (one acre-inch is 27,156 gallons). If you are going to apply 20 ppm of Active Ingredient chlorine, you have to add 133 pounds of Ca(OCl)2 per week. This will certainly factor in for system cost and infrastructure. • Irrigation Flow Rate: What is the flow rate of the irrigation system? For example, if it applies water at 200 gallons per minute, your injection system needs to add Ca(OCl)2 at approximately 23 grams per minute. Contact time: This refers to the amount of time the disinfectant needs to contact the target microorganism to inactivate it. Contact time can be the time the water is exposed to UV, or how long water and chlorine are in the irrigation distribution pipe before the water contacts the crop.

Interaction with Amendments: If using Fertigation or Chemigation, will the disinfectant react with the fertilizer or pesticide?

Worker Safety and Protection: Disinfectants can be hazardous to humans. Therefore, worker safety should be a key consideration. A grower should consider the degree of worker competence available to operate the equipment and the type of training required.

Antimicrobial Pesticide Products – Chlor ination

While the addition of chlorine has been shown and widely used as an effective solution to orifice or emitter clogging due to bacterial growth, it can also increase the microbial quality of agricultural production water by potentially reducing the levels of bacterial pathogens of human concern and indicator organisms, such as generic E. coli. The use of chlorine is a very common disinfectant that is widely used across the food industry. It is relatively inexpensive, effective against a broad spectrum of microorganisms, and available in several forms. This includes liquids (sodium hypochlorite), powders (calcium hypochlorite), and gas (chlorine gas). Regardless of delivery, the active form of chlorine that kills or inactivates microorganisms is hypochlorous acid. This chemical is formed when chlorine reacts with water.

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