1. (a) When selecting water treatment processes at small CWSs, the design shall clearly demonstrate consideration of the following:

   1. (1) Maximizing the effectiveness of treatment;
   2. (2) Including sufficient controls and monitors to identify treatment performance and aid in operation;
   3. (3) Supporting reliability and flexibility of operations;
   4. (4) Selecting processes with low capital and operational costs and energy demand;
   5. (5) Designing equipment to be easily repaired or replaced in-kind to minimize operational downtime;
   6. (6) Sizing and configuring equipment consistent with the practices and standards of the professional water treatment industry; and
   7. (7) Minimizing waste residuals generation and preventing impacts to the environment.
2. (b) Where filters are proposed or required, filter sizing shall minimize head loss and maximize treatment efficiency.

3. (c) Where filter backwash is required, backwash controls shall be designed to:

   1. (1) Initiate a backwash based on volume of water treated, differential pressure, or contaminant breakthrough and not based on filter run time; and
   2. (2) Minimize backwash waste volume.
4. (d) Any non-domestic discharge shall be registered, permitted, or both as required by local, state, and federal authorities.
5. (e) Containers storing treatment chemicals shall be constructed of materials compatible with the stored chemicals and shall provide secondary containment for at least 110 percent of the stored volume.

6. (f) If treatment is proposed or required, the final design shall:

   1. (1) Describe the proposed treatment process, including how the process functions conceptually;
   2. (2) Include a schematic representation of the treatment process;
   3. (3) Describe the equipment, chemical(s), plumbing, and electrical control systems that represent a complete treatment process;
   4. (4) Describe the anticipated treatment wastes and their disposal, in accordance with Env-Dw 405.24;

   5. (5) Include a tabular summary of laboratory sampling results analyzed by a New Hampshire- accredited laboratory, which identifies:

      1. a. The target contaminant(s) and treatment goals; and
      2. b. All other water quality parameters, by name and concentration, that might affect or be affected by the treatment process;

   6. (6) Identify the configuration of all components of the treatment process, including:

      1. a. The rationale for a series or parallel configuration;
      2. b. The number of trains of equipment; and
      3. c. A description of each pretreatment process;

   7. (7) Identify the design criteria used for each treatment component of the process, including:

      1. a. The hydraulic loading rate;
      2. b. The detention time or empty bed contact time;
      3. c. The backwash or regeneration flow rate, and frequency, volume of discharge, and anticipated contaminant concentrations of backwash or regeneration events; and
      4. d. The criteria used to establish the need for filter backwash or media regeneration;

   8. (8) Include a sampling tap with a smooth outlet nozzle to be installed between each treatment unit process and identify plumbing appurtenances throughout the treatment sequence, including:

      1. a. Connecting pipe size, isolation valves, check valves, unions, and bypasses;
      2. b. Meter(s) and their type including whether indicating, totalizing, or recording; and
      3. c. Flow restrictors and their rating;

   9. (9) Identify measuring, control, and communication or alarm equipment, including:

      1. a. Chemical feed pump pacing method and associated equipment;
      2. b. Flow switch interrupt of chemical feed equipment when there is no production flow; and
      3. c. Other automatic monitoring and communication devices;

   10. (10) For each treatment chemical to be used:

       1. a. Specify the chemical feed rate and the target dosage;
       2. b. Provide documentation demonstrating that the chemical is approved for drinking water use in accordance with the American National Standards Institute (ANSI) standard 60 as required in Env-Dw 403; and
       3. c. A copy of the safety data sheet (SDS) for that chemical; and
   11. (11) Include a water quality monitoring plan for determining the quality of the treated water and waste flows, as described in Env-Dw 405.26.
7. (g) Flow mix, if proposed, shall be in accordance with Env-Dw 402.04.
8. (h) A sampling point shall be provided after the last point of chemical injection with consideration given to adequate mixing. If atmospheric storage is located prior to the first customer, sampling points shall be provided both upstream and downstream of the atmospheric storage tank.

Source. #14158, eff 12-25-24