NWRI Assesses Recycled Water Criteria for California

The National Water Research Institute (NWRI) released two reports that evaluate different aspects of recycled water criteria for the state of California. One report provides conclusions as to whether recycled water used to irrigate food crops in California is sufficiently protective of public health, while the second report evaluates the suitability of a potential analytical technique to assess water quality during the recycled water treatment process.

California has led the nation in developing drought-resistant, sustainable water supplies through the use of water recycling—treating municipal wastewater for beneficial purposes such as irrigation, industrial processes, toilet flushing, and replenishing groundwater basins. Over 250 water-recycling plants currently operate in the state. According to survey results released by the California State Water Resources Control Board in 2011, over 650,000 acre-feet of wastewater is being recycled in the state per year. California is now in the process of increasing the amount of recycled water used over the next two decades by an additional 1 to 2 million acre-ft per year.

The first report, “Review of California’s Water Recycling Criteria for Agricultural Irrigation,” addressed the risk of exposure and infection from waterborne pathogens, such as Cryptosporidium and E. coli, due to the irrigation of a wide variety of food crops using recycled water.

Key issues addressed include:

• Characterizing “safe” recycled water for use in irrigation.
• Appropriate assumptions regarding an acceptable risk to public health.
• Relevancy of current criteria for reducing viruses and using chlorine disinfection.
• Need for a “multiple barrier” of treatment processes to remove microorganisms.
• Use of turbidity as a valid parameter to assess the performance of treatment processes.
• Standards used to clarify and define “secondary wastewater treatment,” which involves biological treatment processes to remove contaminants and/or bacteria.
• Use of total coliform bacteria to assess the effectiveness of disinfection in reducing microorganisms.
• Ability of crops to take in viruses through their root systems, leaves, and other points of entry, and any associated risks to public health.

The focus of the second report, “BDOC as a Performance Measure for Organics Removal in Groundwater Recharge of Recycled Water,” was on the suitability of using one water quality-monitoring tool over another.

In this report, a panel evaluated the use of total organic carbon (TOC) to assess the performance of groundwater recharge facilities and Biodegradable dissolved organic carbon (BDOC) as a monitoring alternative. They prepared sections on:

• History of TOC as a performance measure.
• Water quality changes during groundwater recharge using various chemical parameters.
• Two alternative options involving the use of BDOC in place of TOC.

Click here and here to view the reports.   

Source: NWRI