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Description
Renewed European strategies and policies, with a strong focus on the European Green Deal and EU Circular Economy Action Plan (released in December 2019 and March 2020, respectively) stipulate that WWTP should become water resource recovery facilities. In the plants with anaerobic sludge digestion, the return liquors from dewatering of digested sludge (sidestream) contain high concentrations of ammonia nitrogen and phosphorus. These special characteristics bring new opportunities for implementing sustainable technologies for nutrient recovery. The aim of the project is to develop and explore an integrated nitrogen and phosphorus removal and recovery (INPORR) technology in sidestream and, consequently, strengthening the scientific career of Principal Investigator.
The novelty of the INPORR technology lies in the integration of phosphorus and nitrogen recovery and assembling these processes with the advanced, energy efficient process (deammonification) for nitrogen removal. The INPORR technology consists of three stages: 1) phosphorous recovery during chemical struvite precipitation, 2) nitrogen recovery using gas permeable membrane (GPM), and 3) deammonification for polishing nitrogen removal. The nutrients will be recovered in the form of potential fertilizers (ammonium sulphate and magnesium ammonium phosphate). In parallel, a reference technology, consisting of the phosphorus recovery unit and deammonification reactor, will be operated. The INPORR project includes both fundamental research and industrial research. Both lines will be compared in terms of the overall nitrogen removal performance, energy consumption, and greenhouse gas (N2O) production. A mathematical model of both lines will be built in the GPS-X simulation platform. After calibration and validation the model will be used a decision-making tool for designing or operating WWTPs in the view of reducing the environmental impacts of the nutrient removal/recovery processes.
Summary of project results
The INPORR project explored innovative methods to address sustainable nutrient management in wastewater treatment plants by focusing on nitrogen (N) and phosphorus (P) removal and recovery. Improper management of these nutrients can lead to eutrophication, harming water quality and ecosystems. the INPORR project aimed to develop a laboratory-scale system to enhance nutrient recovery, support a circular economy, and promote sustainable water management practices.
To achieve these goals, a laboratory-scale prototype setup was designed within the framework of the INPORR project. Struvite precipitation, membrane distillation (MD) using gas-permeable membranes (GPM), and deammonification were combined. This setup was intended to optimize nutrient recovery and reuse, focusing on producing fertilizers, such as ammonium sulfate and struvite. Under controlled conditions with synthetic wastewater simulating sludge digester liquor from the Gdynia-Dębogórze WWTP, the system achieved promising nutrient removal efficiencies of 96% for N and 100% for P, with an average combined N+P removal efficiency of 98%. Nutrient recovery efficiencies were also promising, reaching up to 78% for N and 100% for P, with an average combined recovery efficiency of 89%. These results reflect the system’s potential to significantly enhance nutrient recovery and resource reuse, even though the tests were not fully based on real sludge digester liquors.
The primary beneficiaries of the INPORR project include wastewater treatment operators and policymakers. Operators could see pathways to resource recovery and cost reductions, while policymakers could gain insights to support sustainable nutrient management policies. Though not yet commercially ready, with further optimization investigations, the INPORR system establishes a base that could eventually offer a market-ready solution for reducing nutrient discharge, enhancing resource recovery, and promoting a circular economy in wastewater management practices.