New Hampshire Code of Administrative Rules
Env - Department of Environmental Services
Subtitle Env-Ws - Division of Water
Chapter Env-Ws 300 - NEW HAMPSHIRE DRINKING WATER RULES
Part Env-Ws 347 - BEST AVAILABLE TREATMENT - ORGANICS
Section Env-Ws 347.06 - Variances from the MCL Disinfection Byproducts

Universal Citation: NH Admin Rules Env-Ws 347.06

Current through Register No. 13, March 27, 2025

(a) The following shall be the required best technology, treatment techniques, or other means generally available for achieving compliance with the MCLfor total trihalomethanes (TTHM):

(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 trihalomethane (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; and

(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) The department shall require a community water system to install and use any treatment method identified in (a), above, as a condition for granting a variance unless the department determines that such treatment method identified in (a), above, is not available and effective for TTHM control for the system.

(c) 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 department determines that none of the treatment methods identified in (a), above, are available and effective for the system, that system shall be entitled to a variance. The department's determination as to the availability and effectiveness of such treatment methods shall be based upon studies by the system and other relevant information.

(d) If a system submits information intending to demonstrate that a treatment method is not available and effective for TTHM control for that system, the department 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.

(e) Pursuant to Env-Ws 342.05, the department shall issue a schedule of compliance that shall 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:

(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; and

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

(f) If such probability exists, the system shall determine whether any of these methods are technically feasible and economically reasonable, and that the TTHM reductions obtained shall be commensurate with the costs incurred with the installation and use of such treatment methods for that system.

(g) If the department determines that a treatment method is available, the department shall require the system to install and use that treatment method in connection with a compliance schedule. Determination shall be based upon studies by the system and other relevant information. In no event shall the department require a system to install and use a treatment method not described in (a) or (c), above, to obtain or maintain a variance from the TTHM rule or in connection with any variance compliance schedule.

(See Revision Note at chapter heading Env-Ws 300) #6521, eff 6-4-97; amd and renumbered by #7735, eff 8-2-02 (formerly Env-Ws 347.70); ss by #8497, eff 11-30-05 (formerly Env-Ws 347.71 )

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