Evaluation of the role of urban domestic wastewater treatment systems for greenhouse gases emissions in China

Abstract

Rapid urbanization has exacerbated the dual challenge of mitigating water pollution and reducing greenhouse gas (GHG) emissions. The present study offers insights into the actual role of urban domestic wastewater treatment systems by shedding light on their capacity to act as GHG emitters. We introduce a modelling framework to calculate GHG emissions from wastewater treatment systems in China over the past two decades. Our analysis showed that treated wastewater volume increased by over 4.5 times, but GHG emissions also increased by 2.9 times. The annual emissions from wastewater treatment were -on average- nearly 60 Tg CO2-eq over the past two decades, accounting for <1% of the total national emissions. We also found a significant spatial variability with thirteen developed areas contributing >70% of the GHG emissions. Constructions and operations of wastewater treatment systems approximately accounted for 17% and 83% of the GHG emissions, respectively. Our study also proposes a hierarchical governance framework based on ten major regions that could maximize the efficiency in mitigating water pollution and GHG emissions in China.