NWRI Independent Advisory Panel Report
Review of California's Water Recycling Criteria for Agricultural Irrigation
Prepared for the California Department of Public Health (CDPH)
Pub No. NWRI-2012-03
The 2012 report, “Review of California’s Water Recycling
Criteria for Agricultural Irrigation,” was developed in response
to increased interest in expanding the amount of recycled
water used for agricultural purposes.
It specifically 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.
The report was prepared by a panel of nine experts jointly led by Robert C. Cooper, Ph.D., who is Professor Emeritus of the School of Public Health at the University of California, Berkeley, and Adam W. Olivieri, Dr.P.H., P.E., the Vice President of EOA, Inc., a public health and environmental engineering consulting firm based in Oakland, Calif.
Cooper has published more than 70 papers on water quality and infectious disease, while Olivieri is an expert on the technical and regulatory aspects of water recycling and public health risk assessment.
Key issues addressed by the panel 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.
In the report, the panel includes responses to each of these issues, as well as provides suggestions to refining the State’s Water Recycling Criteria.
Among the conclusions, the panel stated that “current agricultural practices that are consistent with the [Water Recycling Criteria] do not measurably increase public health risk, and that modifying the standards to make them more restrictive will not measurably improve public health.”
Members of the panel met at the CDPH facility in Richmond, California, in February 2012.
About the Panel
The panel included nine nationally recognized experts
in the fields of public health microbiology and virology, quantitative microbial risk assessment, public health infectious diseases and epidemiology, water reuse,
food safety and hazard analysis, agricultural practices, irrigation management, emerging contaminants
of concern (i.e., waterborne infectious agents),
and water and wastewater treatment effectiveness.
Together, the panel has well over 150 years of
combined experience investigating water reuse
and potential public health issues.
While the panel was formed in 2008, it did not begin work until the spring of 2010. Over a 2-year period, the panel held four meetings, a number of subcommittee meetings, and numerous conference calls. The panel meetings included the opportunity for stakeholder input in clarifying the panel’s charge, exchange of information, dialog with the panel, and consideration of comments from SWRCB and CDPH staff on this draft report, which was prepared by the Panel and provides the results from the deliberations.
Member of the panel include:
- Chair: Robert C. Cooper, Ph. D., University of California (Berkeley, CA)
- Vice Chair: Adam W. Olivieri, Dr. PH, P.E., EOA, Inc. (Oakland, CA)
- Michael D. Cahn, Ph.D., University of California, Cooperative Extension (Salinas, CA)
- John Colford, Jr., M.D., Ph.D., MPH, University of California (Berkeley, CA)
- James Crook, Ph.D., P.E., Water Reuse Consultant (Boston, MA)
- Jean-François Debroux, Ph.D., Kennedy/Jenks Consultants (San Francisco, CA)
- Robert Mandrell, Ph.D., U.S. Department of Agriculture (Albany, CA)
- Trevor Suslow, Ph.D., University of California, Davis (Davis, CA)
- George Tchobanoglous, Ph.D., P.E., NAE, University of California, Davis (Davis, CA)
- Learn more about Recycled Water Regulations and Guidance on the CDPH website.
- View other NWRI Panel Reports for CDPH.
- Learn more about the NWRI Panel Process.
- View NWRI Panel Reports for other agencies.
- View other reports on the topic of water reuse.