Energy from Wastewater Treatment

Abstract The need to conserve ecology and environment and the role played by the process of treating wastewaters before their disposal into natural water bodies is a matter of common knowledge. Though wastewaters can be treated by a physical, chemical, or biological process, or even through a combination of these, biological treatments are inherently more attractive due to their “green” attributes, sustainability, and minimal impact on the environment. However, some of the most widely practiced biological wastewater treatment processes, such as activated sludge process or its modifications, are highly energy intensive. Our awareness of the need for environmental conservation has also made us realize that most of the energy generation practiced at present, depending to a great extent on fossil fuels, is unsustainable. This has opened up our quest for renewable energy. Along with energy generation through renewable sources, the need to practice energy conservation is also necessary if it needs to be a sustainable process. Therefore, the focus has now shifted from biological wastewater treatment processes that are “efficient” to those that are also less energy intensive, or energy-neutral, or even better, net energy producers. The most promising processes are anaerobic wastewater treatment resulting in biogas generation, biological wastewater treatment with hydrogen production, and biological wastewater treatment coupled to power generation through the use of microbial fuel cells (MFCs). While anaerobic wastewater treatment has been in use for quite some time, the current focus is on making it more energy efficient and maximizing the energy production through innovations in reactor design. Dark fermentation of organic-rich wastewaters using appropriate physical and chemical operating environments can produce substantial quantities of hydrogen. Though MFCs are still in a nascent stage, they have high potential for simultaneous wastewater treatment and electricity generation.