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 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.
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.
Constructed 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.
Permeable Reactive Barriers
Permeable 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.
Membrane Bioreactors (MBRs) have long been used for the removal of organic matter and nutrients from wastewater. Despite the advantages of MBR systems with elevated concentration of sludge, such as very high contaminant removal efficiency, lower bioreactor size requirement, and superior effluent quality, this technique faces a crucial challenge, fouling. For decades, increasing the hydrophilicity of the membranes has been considered to be the only option to diminish, not overcome, the fouling problem. However, nature has provided us with a fascinating material that has proven not to adsorb or have affinity to the biological or any other hydrophobic components present in ecosystem: cellulose.
The Center aims to develop a multi-layer antifouling membrane using sustainable biomass-derived nanocellulose as a barrier layer for contaminants. It is hypothesized that the large number of hydroxyl moieties on the cellulose structure will hinder the fouling of hydrophobic components on the membrane and will thus extend the life-time of the membranes and lead to extensive energy savings in transmembrane pressure and membrane backwashing.
Conventional drainfields, also known as leach fields or shallow, narrow drainfields, are soil treatment units designed to take advantage of the natural capacity of local soil to treat wastewater dispersed from a septic tank. Conventional drainfields typically consist of a series of gravel-filled trenches containing perforated pipes through which waste water from the septic tank is dispersed. However, little research has been conducted on the microbial communities in the soil conducting the nitrification / denitrification processes, e.g. their exact metabolism and ecology, nor has a significant amount of research been conducted on improving treatment capacity through use of different materials. The Center is currently conducting monitoring and experiments related to several conventional drainfields installed in Suffolk County. Our goal is to better understand how soil microbes are functioning, allowing us to potentially improve current designs.