Online Sensor for Wastewater Phosphorus Recovery

EPA Grant Number: SU839291
Title: Online Sensor for Wastewater Phosphorus Recovery
Investigators: Winkler, Mari
Institution: University of Washington
EPA Project Officer: Page, Angela
Phase: I
Project Period: February 1, 2018 through January 31, 2019
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2017) RFA Text |  Recipients Lists
Research Category: P3 Awards , Sustainability , P3 Challenge Area - Water


Wastewater treatment plants (WWTP) are designed mainly for removing nutrients, such as phosphorus, to prevent eutrophication in the receiving waters. Secondary goals of wastewater treatment are related to sustainability, which include reduction of chemical usage and enhancement of resource recovery. Phosphorus recovery is gaining importance as the global phosphorus reserves, a non-renewable resource essential for all human existence, are projected to deplete in the next 40-110 years. Phosphorus removal from wastewater can be achieved by chemical precipitation or enhanced biological phosphorus removal (EBPR). EBPR is the more cost effective and environmental friendly method as it does not require non-renewable minerals and the produced sludge can be utilized for phosphorus recovery. Conversely, chemical precipitation has many disadvantages such as extra waste handling, chemical cost, and the inability to recover phosphorus as fertilizer. Successful EBPR process requires a stabilized microbial community and if not carefully designed it can lead to system failure. Also, some EBPR plants require external carbon dosage, which can lead to expensive operational costs if not optimized. Due to these challenges, EBPR was not integrated at most WWTPs for phosphorus removal. In fact, less than 5% of the WWTPs in the US can currently employ phosphorus recovery with EBPR.


The objective of this project is to develop an innovative sensor technology that enables online monitoring and controls of the EBPR process. It will be the first sensor to provide reliable and accurate real-time measurements of phosphate in wastewater and will create a paradigm shift in wastewater engineering by simplifying operations, increasing removal/recovery efficiencies and reducing chemical usage at EBPR facilities.


The development of a phosphate sensor remains an area of active research, with few options available on the market and none capable of accurate quantification in complex wastewaters. During the EBPR process, secondary metabolites (K+ and Mg2+) are known to tightly couple with phosphate ions in a fixed molar ratio, by which the phosphate concentrations can be indirectly quantified. This indirect quantification strategy has been demonstrated by previous research, where a key environmental ion (e.g. sulfate) was successfully quantified from an array of secondary ions. However, quantification of phosphate from secondary metabolites has not been previously explored. Therefore, we propose a sensor technology that combines signals from the commercially available K+ and Mg2+ probes to indirectly quantify phosphate ions in wastewaters. After the sensor is developed, control instructions will be written to enable online controls of EBPR process.

This design requires an interdisciplinary student team with knowledge in wastewater engineering, microbiology and computer science. Therefore, this project will educate students from different disciplines about the importance of nutrient removal and resource recovery in wastewater treatment. The PI and the student team will present the project in classrooms, at conferences and routine meetings with local public agencies. The team will also be encouraged to present this project in their respective department to educate a broader group of students on sustainability.

Expected Results:

The output of this project is a sensor technology that enables accurate in-situ measurements of phosphate ions in wastewater and on-line controls of EBPR process. This online sensor and control technology will be tested with a lab-scale EBPR reactor to evaluate its ability for quantifying the phosphate concentrations and success for improving system efficiencies. Phosphate ions in the reactor will be simultaneously measured by the sensor and conventional colorimetric method, then the two datasets will be statistically compared for similarity. To evaluate the success for improving the system efficiencies, process parameters of the reactor such as effluent phosphate concentrations and carbon additions will be compared before and after implementation of the technology. For future research objectives, the proposed technology can be implemented at full-scale facilities to measure the increase in fertilizer production and savings in chemical costs.

With online phosphate monitoring and controls, EBPR facilities are expected to produce higher effluent quality and increase phosphorus recovery. The proposed technology will also make it more feasible to retrofit conventional facilities for biological phosphorus removal. With more EBPR plants, the potential for phosphorus recovery also increases. This will not only minimize pollution but also extend the lifetime of our diminishing phosphorus reserves to improve national security and independence and lead to a more sustainable nutrient cycle. Furthermore, because the recovered phosphorus can be sold as fertilizer, we can also expect development of local economies with marketable phosphate fertilizer. Consequently, the potential outcomes of this project will cover the three aspects of sustainability by (1) improving water quality and securing fertilizer production for people, (2) promoting the prosperity and local economies with increased marketable fertilizer production and (3) protecting the planet with reduced mining of nonrenewable resources and increased sustainable fertilizer production.

Supplemental Keywords:

treatment technologies, sustainable water management, water treatment