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Onsite Wastewater Treatment Systems

The goal of the NYS Center for Clean Water Technology is to develop next generation approaches for handling household wastewater that are more efficient at removing nitrogen and other contaminants, less expensive, easier to operate, and smaller in size. While our primary focus is on solving the nitrogen issue in Suffolk County, the solutions developed by the Center will be applicable to other parts of the United States and globally.  

For inquiries related to the Center's wastewater research please contact Dr. Stuart Waugh, Senior Research Scientist.

Nitrogen Removing Biofilters (NRBs)

Innovations in onsite treatment of wastewater have produced biofilters designed to take advantage of naturally occurring soil microbes to achieve significant nitrogen removal by nitrification of influent nitrogen and subsequent denitrification of nitrate. Such nitrogen removing biofilters (NRBs) generally consist of a nitrifying sand layer placed over a denitrifying mix of sand and lignocellulose.  Since NRBs are passive systems in which water flows by gravity, are constructed with locally available material, and do not require aeration, installation, operation and maintenance costs are minimized. The Center has installed three pilot systems at the Massachusetts Alternative Septic System Test Center (MASSTC) based on variations of NRB technology all of which have achieved ~ 90% reduction of TN in the final effluent since their installation in the Fall of 2016.  NRBs also provide significant attenuation of pathogens, pharmaceuticals, and personal care products.

Nitrogen Removing Biofilters Fact Sheet


FlexTreat Biosystem™

The Center has been developing a unique onsite wastewater treatment system, trademarked as FlexTreat Biofilter™, that reduces nitrogen below ten mg/L in a similar footprint and cost as commercially available I/A systems.  Based on the column experiments performed in our Wastewater Research and Innovation Facility (WRIF), a patent has been obtained.  The patent-pending process uses an attached growth process to simplify operations and is adaptable to changing influent TKN concentrations and daily design flow.  Input variables such as hydraulic loading, oxygen requirements, and recycle ratio,  provided via a graphical user interface, are used by the operations and maintenance service provider to optimize performance.  The system uses a unique flow distribution system to eliminate flow cross-circuiting within the nitrification chamber.  The nitrification media is a propriety blend of media that enhances performance at high loading rates.   The principle of surface tension over a weir is used to prevent cross-circuiting within the denitrification chamber that uses woodchips as a carbon source and media for nitrifying bacteria to dominate the anoxic biological environment.  The Center has constructed and is monitoring a full-scale prototype currently installed at the WRIF which will serve to inform the design of future systems to be installed within a residential setting.

Phosphorus Removal & Recovery

P DiagramRemoval of phosphorus (P) from onsite wastewater is vital when residences are near freshwater rivers or lakes, or where fractured bedrock can channel nutrients quickly to groundwater and surface water. Successful removal of P from septic tank effluent (STE) is critical to minimize nutrients loading to waterbodies. The Center team aims to develop affordable, reliable, and effective onsite wastewater treatment technologies to remove P from wastewater, groundwater, and surface waters utilizing multiple approaches including adsorption, precipitation reactions and microbial uptake, while concurrently evaluating the performance and function of P removing OWTS. The Center is also developing practical, cost-effective methods of P recovery and re-use for agricultural or other applications. The current focus of the research and development activities include:

  • Evaluate P removal performance by current onsite wastewater treatment systems, such as NRBs and other I/A systems.
  • Investigate P attenuation and mobilization mechanisms in current OWTSs and the surrounding soils.
  • Evaluate and identify the optimal commercially available P removal technologies for onsite wastewater treatment.
  • Research on natural-based materials for P removal and recovery from onsite wastewater and develop modular-based filtration system for implementation.
  • Develop in-situ P sensors that could be used to monitor P removal performance in OWTSs.

For inquires related to phosphorus removal and recovery technologies of the center’s research, contact Dr. Xinwei Mao, Associate/Research Director for the Phosphorus program.

Constructed Wetlands

WetlandConstructed wetlands are engineered systems planted with native wetland species that remove pollutants from water through natural biological, chemical and physical processes. Water flows vertically or horizontally through a porous medium and are subject to treatment by passage through the media and plant roots which support sites for microbial activity. These systems are less expensive to construct and can be more effective at treating contaminants than traditional systems used for wastewater treatment. The Center has installed experimental wetlands systems collaboratively on Long Island and at MASSTC.

Constructed Wetland Fact Sheet

Constructing a Wetland at Uplands Farm

Permeable Reactive Barriers

PRBPermeable reactive barriers (PRBs) are trench systems installed at a depth allowing them to be installed to intercept groundwater contaminated with nitrogen before it discharges into coastal waters.  Since nitrogen in groundwater is typically nitrified, these trenches are filled with lignocellulose, wood products and have been shown to be highly effective at removing nitrogen.  The Center has been testing small pilot systems and will continue to explore the use of PRBs in coastal zones.

Permeable Reactive Barrier Fact Sheet

Town of Brookhaven and CCWT Funded to Install and Monitor a Permeable Reactive Barrier (PRB) at Fire Island’s Davis Park Marina

Sequencing Aerated Biofilm Reactor

SABRThe Center has been developing a novel sequencing aerated biofilm reactor (SABR) using synthetic media and a polishing unit with unique hydraulic and aeration patterns to efficiently remove nitrogen from septic tank effluent at a smaller footprint and minimal external carbon amendment. The impacts of operation conditions, various wastewater strengths, and different types of media on nitrogen and organic matter removal were evaluated in bench-scale SABRs. The unique intermittent aeration strategy and the associated hydraulic pattern facilitated efficient N removal without external carbon or alkalinity amendment. The Center has constructed a pilot-scale prototype at the WRIF to validate the optimal operation conditions obtained at bench-scale tests, and is investigating the SABR long-term performance.