The impact of wastewater treatment plants on global climate change

Abstract Wastewater treatment plants (WWTP) play a crucial role on environmental preservation. The use of appropriate technologies, along with well-established operational strategies, may enable the removal of several pollutants from wastewaters, such as organic matter, nitrogen and phosphorus, avoiding their adverse impacts on the environment. Despite the benefits of implementing the WWTP, their operations can also cause polluting effects, mainly associated with the emission of greenhouse gases (GHG), among which carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). While contributions to CO2 generation are mainly related to energy consumption within the WWTP boundaries, CH4 and N2O emissions are associated with biological carbon and nitrogen conversion processes, such as methanogenesis, nitrification and denitrification. In this chapter, the role of different processes in GHG production is assessed. Besides, operational strategies to minimize GHG emissions from WWTP are also addressed, including the control of several variables within the plants facilities, such as dissolved oxygen concentration, applied load, temperature, pH, hydraulic and solids retention time. Treatment approaches for GHG streams that are inevitably produced and innovative processes, such as Anammox, Coupled Aerobic-Anoxic Nitrous Decomposition Operation and cocultures of bacteria and microalgae, capable of generating less GHG and allowing better use of wastewater resources, are also described. Finally, the effects of climate change and its associated consequences (e.g., increased rainfall intensity and temperature), on the performance and operation of current wastewater treatment systems are presented.