15A NCAC 18C .1514. TREATMENT TECHNIQUES FOR TOTAL TRIHALOMETHANES

(a)  The following have been identified as the best technology, treatment techniques or other means generally available for achieving compliance with 15A NCAC 18C .1517(3):

(1)        Use of chloramines as an alternate or supplemental disinfectant or oxidant;

(2)        Use of chlorine dioxide as an alternate or supplemental disinfectant or oxidant;

(3)        Improved existing clarification for THM precursor reduction;

(4)        Moving the point of chlorination to reduce TTHM formation and, where necessary, substituting for the use of chlorine as a pre‑oxidant, chloramines, chlorine dioxide or potassium permanganate;

(5)        Use of powdered activated carbon for THM precursor or TTHM reduction seasonally or intermittently at dosages not to exceed 10 mg/L on an annual average basis.

(b)  A community water system or a non‑transient, non‑community water system shall install and use any treatment method identified in Paragraph (a) of this Rule as a condition for granting a variance unless the Secretary determines that such treatment method is not available and effective for TTHM control for the system.  A treatment method shall not be considered to be "available and effective" for an individual system if the treatment method would not be technically appropriate and technically feasible for that system or would only result in a marginal reduction in TTHM for the system.  If upon application by a system for a variance, the Secretary determines that none of the treatment methods identified in Paragraph (a) of this Rule is available and effective for the system, that system shall be entitled to a variance under the provisions of 15A NCAC 18C Section .1600.  The Secretary's determination as to the availability and effectiveness of such treatment methods shall be based upon studies by the system and other relevant information.  If a system submits information intending to demonstrate that a treatment method is not available and effective for TTHM control for that system, the Secretary shall make a finding whether this information supports a decision that such treatment method is not available and effective for that system before requiring installation and use of such treatment method.

(c)  Pursuant to 15A NCAC 18C .1604 (c) through (g), the Secretary shall issue a schedule of compliance that may require the system being granted the variance to examine the following treatment methods to determine the probability that any of these methods will significantly reduce the level of TTHM for that system, and if such probability exists, to determine whether any of these methods are technically feasible and economically reasonable, and that the TTHM reductions obtained will be commensurate with the costs incurred with the installation and use of such treatment methods for that system:

(1)        Introduction of off‑line water storage for THM precursor reduction;

(2)        Aeration for TTHM reduction, where geographically and environmentally appropriate;

(3)        Introduction of clarification where not currently practiced;

(4)        Consideration of alternative sources of raw water;

(5)        Use of ozone as an alternate or supplemental disinfectant or oxidant.

(d)  If the Secretary determines that a treatment method identified in Paragraph (c) of this Rule is technically feasible, economically reasonable and will achieve TTHM reductions commensurate with the costs incurred with the installation and use of such treatment method for the system, the Secretary shall require the system to install and use that treatment method in connection with a compliance schedule issued under the provisions of 15A NCAC 18C .1600.  The Secretary's determination shall be based upon studies by the system and other relevant information.  In no event shall the Secretary require a system to install and use a treatment method not described in Paragraphs (a) or (c) of this Rule to obtain or maintain a variance from 15A NCAC 18C .1517(3) or in connection with any variance compliance schedule.

 

History Note:        Authority G.S. 130A‑315; P. L. 93‑523; 40 C.F.R. 141;

Eff. October 1, 1983;

Transferred and Recodified from 10 NCAC 10D .1637 Eff. April 4, 1990;

Amended Eff. August 1, 1990.