 |
Virginia Administrative Code (Last Updated: January 10, 2017) |
 |
Title 12. Health |
|
Agency 5. Department of Health |
|
Chapter 590. Waterworks Regulations |
Section 500. Disinfection by chlorination
-
A. All water supplies derived from surface water sources in whole or in part shall be disinfected in accordance with 12VAC5-590-1000 until June 29, 1993. It is recommended that a chlorine residual be maintained. Beginning June 29, 1993, every owner of a waterworks shallcomply with the disinfection requirements of 12VAC5-590-420.
B. Owners of waterworks utilizing surface waters as a water supply shall practice prechlorination. The requirement for prechlorination may be waived by the commissioner when warranted.
C. Owners of waterworks utilizing groundwater as a water supply that has been determined by the commissioner to be under the direct influence of surface water, as provided in 12VAC5-590-430, will be required to disinfect. If the commissioner determines that the groundwater supply is surface influenced, the owner shall provide disinfection during the interim before filtration is installed in accordance with 12VAC5-590-420 B 2 f. If filtration is installed prior to June 29, 1993, the owner shall comply with the disinfection requirements of 12VAC5-590-1000 until June 29, 1993. By June 29, 1993, all owners of waterworks using a groundwater source determined to be under the direct influence of surface water shall comply with the disinfection requirements of 12VAC5-590-420.
D. Owners of groundwater systems subject to the requirements of 12VAC5-590-421 A 1 d shall provide a disinfectant residual concentration (C) and contact time (T) to achieve a 4-log inactivation of viruses. CT shall be calculated in accordance with Appendix L, which contains information on calculation methods and contact tank baffling factors.
E. Disinfection profile data and disinfection benchmark data.
1. The owner of any waterworks that has disinfection profile data shall retain this data in graphic form, as a spreadsheet, or in some other format acceptable to the commissioner for review as part of sanitary surveys conducted by the commissioner. Appendix L lists the procedure for developing a disinfection profile.
2. Disinfection benchmarking.
a. The owner of any waterworks that has developed a disinfection profile and that decides to make a significant change to its disinfection practice shall consult with the commissioner prior to making such change. Significant changes to disinfection practice are:
(1) Changes to the point of disinfection;
(2) Changes to the disinfectants used in the treatment plant;
(3) Changes to the disinfection process; and
(4) Any other modification identified by the commissioner.
b. The owner of any waterworks that is modifying its disinfection practice shall calculate its disinfection benchmark using the following procedure:
(1) For each year of profiling data collected, the owner shall determine the lowest average monthly Giardia lamblia inactivation in each year of profiling data. The owner shall determine the average Giardia lamblia inactivation for each calendar month for each year of profiling data by dividing the sum of daily (or weekly) Giardia lamblia inactivation by the number of values calculated for that month.
(2) The disinfection benchmark is the lowest monthly average value (for waterworks with one year of profiling data) or average of lowest monthly average values (for waterworks with more than one year of profiling data) of the monthly logs of Giardia lamblia inactivation in each year of profiling data.
(3) The owner of a waterworks that uses either chloramines or ozone for primary disinfection shall also calculate the disinfection benchmark for viruses using a method approved by the commissioner.
c. The owner shall submit the following information to the commissioner as part of the waterworks' consultation process.
(1) A description of the proposed change;
(2) The disinfection profile for Giardia lamblia (and, if necessary, viruses) and benchmark listed in subdivision E 2 b of this section;
(3) An analysis of how the proposed change will affect the current levels of disinfection; and
(4) Any additional information to justify the change.
Historical Notes
Derived from VR355-18-005.06 § 2.17, eff. August 1, 1991; amended, Volume 09, Issue 17, eff. June 23, 1993; Volume 18, Issue 19, eff. July 3, 2002; Volume 21, Issue 13, eff. April 6, 2005; Volume 25, Issue 05, eff. December 10, 2008; Volume 28, Issue 05, eff. December 7, 2011.