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Center Study Demonstrating Phosphorus Removal from Septic Waste Wins 2022 Best Paper Award

June 7, 2022 - The New York State Center for Clean Water Technology (CCWT) was awarded the 2022 Best Paper Award by the Journal of Sustainable Water in the Built Environment for "Biogeochemical Sequestration of Phosphorus in a Two-Layer Lignocellulose-Based Soil Treatment System", Journal of Sustainable Water in the Built Environment Vol 6, No. 2 (May 2020): 040200002. The award was presented at the 2022 World Environmental and Water Resources Congress in Atlanta, Georgia on June 7, 2022.

In this study, CCWT-students and affiliated researchers investigated the biogeochemical processes that control phosphorus (P) sequestration in a nitrogen removing biofilter (NRB). The oversupply of phosphorus and nitrogen to aquatic systems can lead to eutrophication, the growth of harmful algae blooms, and the overall decline of water quality. While phosphorus is a significant pollutant for freshwater lakes and ponds, recent research has demonstrated that phosphorus can also promote harmful algal blooms in marine ecosystems.

CCWT created NRBs as onsite soil-based wastewater treatment systems which follow an initial septic tank. They consist of a first layer of sand or sandy soil (“nitrification layer”) and a second layer of sand mixed with an organic carbon source, in this case lignocellulose (“denitrification layer”). To date, CCWT has installed more than two dozen NRBs across Suffolk County and anticipates gaining provisional approval from Suffolk County, NY, for their widespread installation later this year.

In the ‘Best Paper’ study, the NRB system tested was effective in the removal of dissolved phosphorus (P) species entering the system as part of the septic tank effluent over a two-year test period. The study revealed that in the sand layer, P was mainly sequestered into iron and aluminum hydroxides through mineral formation and recrystallization reactions and by dissimilatory iron reduction followed by authigenic iron-phosphorus mineral precipitation. In the underlying denitrification layer, P removal by calcium phosphate precipitation was likely the predominant process. Surprisingly, adsorption of P onto mineral phases, which is often highlighted as an important attenuation process in soil treatment systems, only played a minor role.

The results of this study highlight that biogeochemical processes involving iron are very important in the effective long-term sequestration of phosphorus in soil-based treatment systems. When choosing building materials for onsite system construction, particularly when designed for P removal, amorphous and crystalline Fe oxide contents of the material should be evaluated.  In good news, much of the sands found across Long Island are enriched in iron, meaning that NRBs are likely to removal maximal amounts of P.

Director of The New York State Center for Clean Water Technology (CCWT), Dr. Christopher Gobler, said: “The bedrock on which CCWT was founded is research that is grounded in excellent science.  This great honor is evidence that CCWT is engaged in the highest level of scientific research that informs clean water solutions.  While nitrogen is a pollutant of prime concern on Long Island, globally phosphorus is a significant contaminant and even some water bodies across Long Island can be impacted by phosphorus.”

Lead scientist of the study, Laura Wehrmann said: “This study represents an excellent example of the important interdisciplinary work that CCWT graduate students and researchers are carrying out to protect and improve the quality of our local waters.  This is the first study highlighting that NRBs can be very efficient at removing phosphorus, which can drive the eutrophication of water bodies, especially lakes. By deciphering the underlying biogeochemical processes that drive phosphorus sequestration in NRBs, we have gained important insights that allow us to further improve the design of these systems to target both nitrogen and phosphorus.

The Center for Clean Water Technology will be continuing phosphorus research as part of a grant administered by the New York State Department of Environmental Conservation starting in the Fall of 2022. Funding will be used both on Long Island as well as upstate New York, thereby expanding the Center's research efforts and impacted communities.