Wastewater From Drinking Water Systems

What is Drinking Water System Wastewater?
Drinking water systems are all facilities and related infrastructure associated with the collection, distribution and treatment of drinking water. Drinking water treatment wastewater (WTW) is any waste or wastewater that is generated from water treatment processes, construction, operation and maintenance of any of these facilities. Because WTW could include large quantities of sediment (fine particulates containing contaminants), high concentrations of metals or chlorine, high/low pH, and other potentially harmful constituents, the disposal of WTW are regulated to protect human health and the environment.

This fact sheet addresses two options for disposing of WTW, namely discharging to surface water or to groundwater. Additional discharge requirements for certain treatment systems can found in the following fact sheets.

• WD-DWGB-3-22 “Arsenic Removal and Disposal of for Public Water Systems”
• WD-DWGB-22-17 “Disposal of Backwash from Water Treatment Devices at Single Family and Duplex Residences”
• WD-DWGB-22-21 “Methods to Reduce the Concentration of Radionuclides in Drinking Water and Radionuclide Waste Disposal Criteria”

Discharge of WTW to Groundwater
Whether you need a permit for WTW discharges onto or into the ground depends on the type of discharge. In general, the following applies:

Routine WTW Discharges
Discharges that occur at the same location or on a continuous or frequent basis such as treatment plant filter backwash, brine discharges from softeners, and unlined dewatering lagoons are considered routine WTW discharges. These discharges must be registered with DES and BMPs must be followed.

Discharges requiring pH or Chlorine Neutralization
Discharges associated with well rehabilitation or waterline work where shock chlorination is involved require a Temporary Groundwater Discharge Permit. This permit will have conditions to ensure that proper neutralization, solids settling and/or erosion control occurs.

What are some of the best management practices (BMPs) that you will be required to follow?

Examples of BMPs that you must follow when you discharge to groundwater include:

• Erosion Control:
  • Regular inspections of where water is flowing to prevent erosion and sedimentation.
  • Diversion of runoff away from sensitive areas and into areas with sufficient vegetation to filter and slow the flow.
  • Minimization of sedimentation and erosion by using gradual vegetated slopes and surfaces when available.
  • Use of typical erosion control methods such as filter fabric, hay bales, silt fencing, etc. for areas of bare ground or where there are no natural means of filtration and solids settling.
• Suspension of activities during storms or during high water periods.
• Settling and filtration of solids resulting from the use of mechanical equipment to clean delivery lines.
• Minimize the amount of disturbed soil during construction, repair, and maintenance activities.
• Refrain from discharging equipment wash and rinse water containing detergents and surfactants (e.g., detergents, wetting agents, emulsifiers, etc.).

Discharge of WTW to Surface Waters
You will need a federal permit through the National Pollution Discharge Elimination System (NPDES) program to discharge any WTW to a surface water. Surface waters include streams, lakes, ponds, and tidal waters within the jurisdiction of the state, including all streams, lakes, or ponds bordering on the site, marshes, water courses and other bodies of water, natural or artificial. For more information about NPDES program please contact Jeff Andrews at (603) 271-2984 or jandrews@des.state.nh.us.

Prohibited Discharges
The discharge of ANY wastewater containing a regulated contaminant as detailed in the Ambient Groundwater Quality Standards under Env-Ws 1500 is prohibited. These prohibited discharges include:

• Facility discharges from open floor drains where regulated contaminants are used or stored.
• Backwash from activated carbon treatment systems for the removal of chlorinated compounds, volatile organic compounds, or other petroleum and solvent related contaminants.
• Unfiltered or unsettled backwash from arsenic treatment devices.

For Additional Information
For more information concerning water treatment wastewater discharges, temporary discharges to groundwater, or nondomestic wastewater discharges to the ground or groundwater, please visit the DES Drinking Water Source Protection webpage at www.des.nh.gov/dwspp, or call (603) 271-2858.

For additional information, please contact the Drinking Water and Groundwater Bureau at (603) 271-2513 or dwgbinfo@des.state.nh.us or visit our website at www.des.nh.gov/dwgb. All of the bureau’s fact sheets are on-line at www.des.nh.gov/dwg.htm.

Note: This fact sheet is accurate as of January 2007. Statutory or regulatory changes, or the availability of additional information after this date may render this information inaccurate or incomplete.