Synergistic pathways of water quality improvement and GHG emission reduction in wastewater sector on the Qinghai-Tibet Plateau

Greenhouse gas (GHG) emissions from the wastewater sector in the Qinghai-Tibet Plateau (QTP) have been increasing, while improving of water quality in wastewater treatment plants (WWTPs) remains urgent, making coordinated development a crucial objective. In this paper, we conducted an inventory analysis of GHG emissions in the QTP wastewater sector from 2014 to 2018. Additionally, we evaluated changes in water quality and GHG emissions under optimized scenarios involving advanced wastewater treatment technologies and enhanced sludge resource utilization by 2035. The results show that total wastewater GHG emissions in the QTP increased from 0.25 Mt. CO2e to 0.45 Mt. CO2e between 2014 and 2018. However, with an extensive and integrated application of technologies tailored to plateau conditions in wastewater treatment and sludge disposal, the synergistic development of improving water quality and slowing GHG emissions growth is achievable. By 2035, under the scenario of optimizing wastewater treatment processes, the proportion of WWTPs meeting China's Class 1A discharge standard is projected to increase by 57 %, while GHG emissions could be reduced by 35 %, relative to the business-as-usual (BAU) scenario. Furthermore, under the scenario of integrating advanced treatment processes and sludge resource utilization, GHG emissions is expected to be 48 % of that in the BAU scenario by 2035. This study provides insight for the wastewater sector in plateau regions to improve water quality and reduce GHG emissions.