Over the past 5 years, the annual wastewater discharged by Chinese cities increased from 42 billion metric tons to 54.5 billion metric tons; an increase of over 30%. At the same time, China’s goal to address this growing wastewater production also increased drastically, passing 85% in 2012, and is projected to reach 95% by 2020.
But just like any other industrial process, wastewater treatment is also an energy intensive industry with generating concomitant pollutants. Generally, to satisfy discharge standards, wastewater treatment systems employ multiple water purification technologies and techniques, with the goal of isolating contaminants from the water, or to turn them into harmless substances. During this process, treatment plants will use large amounts of electricity, flocculants, disinfectants and other chemicals. It will also produce large amounts of excess sludge and greenhouse gases. All of these create new environmental problems and pollution, leaving wastewater treatment industries with an urgent need to truly revolutionize sustainable models of operation.
As an Associate Researcher at the Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Dr. Xu Wang came up with a “Net Environmental Benefit (NEB)” model to address the challenges surrounding wastewater treatment. He believes that because there are numerous factors involved with wastewater treatment systems, using treatment ratings or water quality compliance ratings alone is not a good measure of success. Instead, the industry should consider the use of emerging NEB metrics, that calculate based on adverse environmental impacts caused by energy consumption, chemicals used and greenhouse gas emissions, plus environmental benefits derived from energy and resource reuse from wastewater and sludge. This comprehensive analysis of treatment facilities’ impact to the overall environment aligns with modern industries’ goal of enhanced sustainability.
Using the NEB model, Xu constructed a multi-factor evaluation framework that takes a wastewater treatment system’s energy efficiency, carbon emissions, and resource recovery into account. Leveraging big data techniques, Xu analyzed almost 20 years’ worth of data on both wastewater treatment systems and socioeconomic factors from over 50 countries and created a time-series model for weighing the trade-offs among assessment metrics over time. Accordingly, Xu projected the environmental benefits from revolutionizing wastewater treatment by the year 2020. These outcomes were published in the prestigious Proceedings of the National Academy of Sciences of the United States of America in 2015.
Viewing wastewater as a resource when designing wastewater facilities will be highly effective in making the whole system more environmentally friendly. Xu’s research provided urban water resource managers with a set of robust decision-making information and efficient measurement tools, and will point the next round of urban water and sanitation infrastructure upgrades to a new, more sustainable direction.