Activated sludge processes are commonly used for efficient treatment of municipal wastewater. The essential mechanism of traditional activated sludge processes is respective transform of pollutants and energy. However, the issue of these processes is the high energy consumption (fossil fuel) and emission of much greenhouse gases (GHG). And the potential organic chemical energy (about 1.5－1.9 kW·h /m3) contained in wastewater has not been explored and utilized．So the wastewater cannot be simply considered as‘waste’, but a valuable resource full of energy, valuable materials and clean water. The direction of future wastewater treatment plant is to put the nutrients，energy and reuse water in one plant, e.g .‘three plants in one’mode. The wastewater treatment plant ( WWTP) would be changed from energy consuming to energy neutral or even energy producing．
The first key point of wastewater treatment process is sludge anaerobic digestion; the second is the capture /separation of influent organic carbon to the maximum extent, and adoption of coupling technology of high efficient sludge anaerobic digestion and cogeneration of heat and power (CHP), which can realize the conversion of COD organic chemical energy to electrical energy. Recently COD capture and carbon redirection technology has emerged around the world. And the projects with COD capture and carbon redirection have been built already. Then, the current ‘carbon capture’ technology was put forward. Based on this the future sustainable wastewater treatment technology route map has been displayed. We are expecting to provide references for the domestic wastewater treatment plant‘carbon neutral’operation, for the development of future sustainable WWTP and ecological recycling water plant．
The electricity consumption in the sewage treatment process accounts for about 1% to 3% of the total electricity consumption of the whole society, but at the same time, the huge “chemical energy” and “heat source” contained in the sewage are far from being extracted and utilized.
The carbon dioxide produced by the electricity consumed in the wastewater treatment process and the chemical energy contained in the wastewater COD are all energy sources that can be reused by humans in the future.
On the other hand, water reuse, policies and partnerships, and emerging disruptive technology solutions are vital to the cause. Specifically, there is an urgent need to shift how we view wastewater treatment and move to sustainable, strategic infrastructure solutions. Wastewater treatment plants are not waste disposal facilities, but rather resource recovery facilities that have the potential to produce clean water, recover nutrients (such as phosphorus and nitrogen), and reduce the dependence on fossil fuels through the production of renewable energy.
Figure 3. Nitrogen cycle in the process of wastewater treatment.
The Future Of Energy And Water
As water and energy demand and supply continue to shift, managing the two resources in tandem will help regions worldwide maintain reliable and sustainable supplies of both. This is of critical importance as the global economy continues to explore new energy and renewable energy sources. But to sustain energy production and a dependable water supply, we must all gain even more detailed understanding of the interdependencies of water and energy systems, balance the needs of all users, and continue to develop technologies that reduce water use and enable water recycling while neutralizing or even creating energy.
Reference：
Jeff Peeters, PE, (2015). The Future Of Energy-Neutral Wastewater Treatment Is Here. Water online : Guest Column. [online] Available at <https://www.wateronline.com/doc/the-future-of-energy-neutral-wastewater-treatment-is-here-0001
By Ji Han
wastewater thinking 