Protecting & Restoring Long Island's Peconic Bays

Water Reuse

Water Re-use

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This category addresses the role of farmland, parks, golf courses, and other open spaces in reducing groundwater nitrogen via water reuse and management of the water cycle around the open space. It includes treating groundwater pumped from existing or new wells that will eventually or intentionally be charged back into the aquifer via irrigation, constructed wetlands, or other novel approaches. It also includes using sewage treatment plant (STP) effluent for water reuse in the same manner. The use of STP effluent is known as direct reuse. The use of groundwater that may have been impacted by septic drain fields can be considered indirect reuse.

The common understanding of water reuse is the use of effluent from an STP to replace and conserve the current source water (groundwater or domestic potable). Potential sources of reuse water include the following:

  • STP effluent that is discharged offshore
  • STP effluent that is discharged to groundwater
  • Groundwater

Because effluent that is discharged offshore causes no groundwater nitrogen loading, its reuse would not be a nitrogen reduction best management practice (BMP) and thus is not included in this assessment.

This BMP category applies only to reuse in open spaces such golf courses, athletic fields, and parks. It uses a golf course as an example for costing and nitrogen load reduction. Other reuse opportunities, such as for industrial cooling or agricultural applications, might be implemented to reduce nitrogen, but they are beyond the scope of this assessment. Similarly, ion exchange systems used in some parts of the domestic water distribution system to control nitrogen below the drinking water limit are inherently removing nitrogen from the area’s water cycle, but extensive modeling would be required to quantify their effect.

Advantages and Disadvantages


  • Conservation of fresh water
  • Potential for nitrogen reduction
  • Reduction in fertilizer use
  • Provides recharge of Long Island’s sole source aquifer


  • Expensive
  • STP effluent requires enhancement to tertiary treatment


Reuse of wastewater or groundwater are assumed to require a feasibility study to determine the best source of water both to achieve water conservation and to reduce nitrogen in the groundwater. The first step of a study would be an evaluation of fertilization practices similar that in Section 7. Next, the study would determine whether the current irrigation practice (i.e., indirect reuse from a well) is already reducing groundwater nitrogen, can be optimized to further reduce nitrogen, or additional nature-based nitrogen removal BMPs could be added. The following considerations define the scenarios for which costs will be developed:

  • Does the current irrigation practice remove nitrogen and does excess irrigation water recharge the aquifer?
  • Does the current irrigation water supply contain appreciable levels of nitrogen, or is there a nearby high groundwater nitrogen zone that can be used?
  • Combined with  fertilizer management, can the current nitrogen-reducing effect of irrigation be enhanced or optimized to further reduce nitrogen?
  • Is a surface runoff BMP such as a wetland needed when irrigation is not occurring and can the open space be used for installation of a surface runoff BMP for itself (e.g., a golf course) and the adjacent and surrounding areas?
  • Is there a groundwater nitrogen reduction benefit from extended or continuous flow from an existing irrigation well to an existing wetland BMP?

These considerations are addressed through the development of cost and permitting requirements for direct reuse and a cost benefit comparison between direct and indirect reuse.


Sewage treatment plants need to be located close enough to the golf course (or other open space area) for water reuse to be feasible.


Permitting would depend on the type, location, and size of the selected water reuse BMP. The following permits are required for installation of a water reuse system that includes a wetland BMP, which would require the most regulatory oversight:

  • U.S. Army Corp of Engineers
  • New York State Department of Environmental Conservation (NYSDEC) Freshwater Permit and/or Tidal Wetland Permit
  • NYSDEC Water Quality Certification
  • NYSDEC State Pollutant Discharge Elimination System (SPDES)
  • Suffolk County Department of Health Services (SCDHS)
  • Town and Village setbacks in close proximity to surface waters or wetlands
    • Town and Village Trustee Permit

Cost Per Pound Nitrogen Removal

Costs are provided for installation of new well for groundwater reuse and use of effluent from an existing STP as Scenarios A and B, respectively, for irrigation of a 150-acre golf course with 75 maintained acres at a watering rate of 14 inches/year (CDM Smith 2020). The well (groundwater) or STP reuse capacity was set at 400 gallons per minute. The STP design was modeled after the wastewater treatment plan proposed for the Shinnecock Bay West subwatershed in Appendix A of the Subwatershed Wastewater Plan (CDM Smith 2020). Costs include $200,000 for a feasibility study, $330,000 for 2,600 feet of new 6-inch piping and a pumped force main, and $60,000 for two 400 gallons per minute (gpm), 5 hp pump station for both scenarios. The groundwater reuse scenario includes an additional $200,000 for three new off-site 4000 gpm, less than 100-foot-deep wells, including design and installation costs and the STP effluent scenario includes $3 million to upgrade to tertiary treatment (Gruttadaurio and Petrovic 2010).

O&M costs for groundwater reuse assume a $7,500 per year salary for servicing in addition to $1,000 annual maintenance and consumables, 10-kilowatt (kW) power, and $2,500 per year parts repair and replacement costs. O&M costs for STP effluent reuse assume a $7,500 per year salary for servicing in addition to $1,500 annual maintenance and consumables, 15 kW power, and $2,500 per year parts repair and replacement costs. The annualized cost includes capital costs annualized over 20 years with a 5% discount rate and the annual average O&M cost.

Costs include the cost of a wetland buffer zone to receive the groundwater or STP effluent when irrigation requirements have been met. For nitrogen reduction estimates, wetland routing was assumed for 20% of the time. For groundwater reuse, nitrogen concentrations of 5 and 10 milligrams per liter (mg/L) are considered and STP effluent is assumed to have a nitrogen concentration of 8 mg/L.

Water Reuse BMP Nitrogen Reduction and Costs

BMP TypeCapital CostO&M CostsAnnualized Total CostAnnual Nitrogen Removal (lb/yr)Cost per Pound Nitrogen Removed
Groundwater reuse$800,000$37,000$100,000$3,080–1,540$32–65
STP effluent reuse $3,600,000 $50,000 $340,000 $2,464$138

The costs presented in the table above reflect optimization of the nitrogen reduction benefit, and do not consider the cost benefit associated with water reuse itself. The Riverhead Water Resource Recovery Facility was installed at the Riverhead STP and has been online since 2016, diverting 450,000 gallons per day (gpd) of STP effluent for in-plant use and irrigation of the adjacent Indian Island golf course (Riverhead Sewer District 2015). The nitrogen reduction benefit resulting from diversion of 350,000 gpd STP effluent and irrigation of the Indian Island golf course was estimated at 1,953 pounds of nitrogen per year (Riverhead Sewer District 2015). The cost to upgrade the Riverhead STP to tertiary treatment was $23.5 million but these costs also include plant upgrades to reduce effluent nitrogen concentrations to comply with the Peconic Estuary total maximum daily load (PEP 2007). In 2010, Gruttadaurio and Petrovic estimated Riverhead STP upgrades for effluent diversion and irrigation of Indian Island would cost $3 million, and that is the plant upgrade cost included in the STP effluent reuse scenario presented in Table 8-1, but this may be an underestimate. In any case, the cost per pound of nitrogen reduction for the Riverhead Water Reuse Recovery Facility may be slightly higher than the scenario presented in Table 8-1, but costs estimated here do not reflect the benefit associated with water conservation, which was also a goal of the Riverhead Water Resource Recovery Facility.


CDM Smith, 2020. Reclaim Our Water Subwatersheds Wastewater Plan. Prepared for Suffolk County Department of Health Services. February 2020.

Gruttadaurio, J. and A.M. Petrovic, 2010. Appendix C: Guidelines for Using Recycled Wastewater for Golf Course Irrigation in the Northeast. Available at:

PEP (Peconic Estuary Partnership), 2007. Total Maximum Daily Load for Nitrogen in the Peconic Estuary Program Study Area, Including Waterbodies Currently Impaired Due to Low Dissolved Oxygen: The Lower Peconic River and Tidal Tributaries; Western Flanders Bay and Lower Sawmill Creek; and Meetinghouse Creek; Terrys Creek and Tributaries. September 2007.

Riverhead Sewer District, 2015. Riverhead Water Resource Recovery Facility for the Peconic Estuary – Golf Course Irrigation. Available at:

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