Raising discharge standards leads to environmental problem shifting in China

The discharge standards for wastewater treatment plants (WWTPs) in China are trending towards increasingly stringent nutrient removal requirements over recent decades. However, the current paradigm for WWTPs has a singular focus on effluent quality, seldom considering the broader environmental consequences of the treatment required to meet these more stringent limits. In this article, the operating data of 17 WWTPs with three different discharge standards were collected. Using an inventory-type approach, greenhouse gas (GHG) emissions and eutrophication potential (EP) of each plant were calculated. Results show diminishing marginal returns in terms of pollution reduction as the level of treatment increases, taking environmental influences into consideration. Therefore, the strictest standards are not the most cost-effective ones in current China. Rather than focusing strictly on point source dischargers and requiring advanced treatments, regulatory agencies should reconsider their water quality protection strategies.