Laboratories may be excited to hear that the State Water Resources Control Board now allows US EPA-approved drinking water methods when testing for Total Coliforms in recycled water samples.
California Title 22 requires the enumeration of Total Coliforms (TC), with allowable TC levels determined by the end use of the recycled water. The testing of TCs must be performed by a laboratory accredited by the California Environmental Laboratory Program (CA ELAP). In order to be eligible to test these recycled water samples, the laboratory must have a TC enumeration method included in their Scope of Accreditation. Currently, the most prominently used method is Multiple Tube Fermentation (MTF), which is included by CA ELAP in their Field of Testing 107 (FOT 107) list of wastewater methods.
Historically, Title 22 methods were chosen from a table of methods listed in the US EPA Wastewater Rule. (This Wastewater Rule is codified in the Code of Federal Regulations at 40 CFR 136.) While the decision to use EPA wastewater methods for detecting TC in recycled water was a logical choice when Title 22 was originally written, the treatment processes in use today produce water that is of far better quality than could have been imagined at that time. Therefore, the use of only wastewater methods may not continue to meet the expanding vision for recycled water in California because today’s recycled water no longer resembles wastewater.
In response to this shifting landscape, in May of 2016 CA ELAP (under the direction of California’s Division of Drinking Water’s Recycled Water Unit) announced that total coliform testing of recycled water could be performed using several of the drinking water methods found in the EPA Drinking Water Regulations at 40 CFR 141. These new allowable methods are listed by CA ELAP in their FOT 101 method list (see chart below).
Acceptable Total Coliform Methods for Disinfected Secondary and Tertiary Recycled Water
|40 CFR 141 (found on FOT 101)||40 CFR 136 (found on FOT 107)|
|SM 9221 B,C||SM 9221 B|
|SM 9222 B||SM 9222 B|
|SM 9223 B Colilert|
|SM 9223 B Colilert-18|
|SM 9223 B Colisure|
The primary rationale for adding drinking water test methods for Title 22 compliance is that recycled water produced today is of much higher quality than wastewater. However, there are additional benefits to using drinking water test methods that labs should consider. For example:
- Public perception: Being able to tell the public that drinking water methods are used to test water quality could help boost public confidence in the use of recycled water.
- Paving the way for Direct Potable Reuse (DPR). California is considering DPR as a future use of recycled water. Several TC methods listed in FOT 101 allow the simultaneous detection of TC and E. coli. Under the EPA drinking water regulation, E. coli is the public notification target. Being able to monitor a disinfection system for both TC and E. coli removal is advantageous if Direct Potable Reuse is an eventual goal for the system.
- Lab efficiency. Some methods from FOT 101 allow a laboratory to use one test to meet multiple regulatory test requirements. For example, select SM 9223B methods could be used to test recycled water, drinking water, source water, ground water, wastewater and others matrices.
- Ease of use. Some of the FOT 101 methods are easier to perform and provide easier-to-interpret results than multiple tube fermentation.
If a laboratory currently has an FOT 101 method on their Scope of Accreditation, they are able to use that method for compliance TC testing under Title 22. If a laboratory does not have an FOT 101 listed in their scope, these methods can be added by following the CA ELAP requirements listed at their website: http://www.waterboards.ca.gov/drinking_water/certlic/labs/index.shtml# under “Application”.
Recycled water should be viewed and treated as a resource, not as waste.
For questions or additional guidance od adopting SM9223B methods for recycled water, please contact Patsy Root, Regulatory Affairs Manager, at firstname.lastname@example.org.