(229e) Utilizing Multi-Criteria Decision Analysis for Holistic Evaluation and Selection of Wastewater Nitrogen Recovery Technologies

Municipal wastewater contains high concentrations of ammonia that if left untreated can lead to a variety of environmental problems such as eutrophication and the production of nitrous oxide (N₂O). Traditionally, wastewater treatment plants (WWTPs) have utilized nitrogen removal technologies such as nitrification-denitrification to produce diatomic nitrogen that is released into the atmosphere. However, nitrification-denitrification is an energy-intensive process that does not produce a usable product. As the emphasis on developing a nitrogen circular economy continues to grow, there is interest in WWTPs implementing nitrogen recovery technologies into their infrastructure. Although multiple technologies that produce different products are being developed, there is no technology that is the industrial standard within WWTPs. As these technologies continue to be developed, and new technologies become available, it will be important for a WWTP to identify which technology should be integrated into their facility. Therefore, a holistic and consistent approach is needed to guide the decision-making process.

This study develops that framework to evaluate 9 different nitrogen recovery technologies to rank which technologies would have the biggest impact on nitrogen circularity. These technologies are evaluated against five indicators: technical, environmental, economic, social, and circularity. Life cycle assessments, techno economic analysis, and process modeling are used to assign values to each of the indicators for the different technologies. For each of those indicators, objective weighting methods such Standard Entropy and CRiteria Importance Through Intercriteria Correlation (CRITIC) are used to identify the importance of each category in the evaluation. Then multi-criteria decision analysis (MCDA) methods such as Analytic Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) are used to compare and rank the different technologies against each other. Ultimately, this framework can be used by existing WWTP facilities looking to integrate nitrogen recovery into their facility to identify the technology that best fits within their system to improve the nitrogen circular economy.