Linking organic matter removal and biogas yield in the environmental profile of innovative wastewater treatment technologies

Abstract Wastewater treatment plants (WWTPs) need to abandon the linear concept and adapt to the circular philosophy integrating standards of technological performance but also environmental, economic and social indicators. However, this change cannot be made by merely replacing one technology, but integrated solutions need to be applied. In this framework, a new strategy of treatment has gained strength in recent years, which consists of recovering organic matter (OM) in the primary treatment and implementing partial nitrification-anammox process as secondary treatment. In this study, three different schemes based on this approach were evaluated from an environmental and economic perspective and compared with a conventional wastewater treatment plant. The three proposed schemes are: i) upflow anaerobic sludge blanket (UASB) + integrated fixed film activated sludge (IFAS); ii) high rate activated sludge (HRAS) and IFAS, and finally, rotating belt filter (RBF) + chemical enhanced primary treatment (CEPT) followed by an IFAS unit. Even though the technological and operational complexity is noteworthy in the schemes based on this strategy, lower environmental impacts were estimated for the first two configurations. However, the consumption of chemicals in the third alternative was detrimental for the environmental performance of the plant, even with higher impacts than those of the conventional scheme for the toxicity-related categories. In this regard, the consumption of energy and chemicals are the main barriers for its successful implementation.