[Carbon Emission Accounting and Emission Reduction Path Analysis of Urban Wastewater Treatment Plants： A Case of a Wastewater Treatment Plant in Shenyang City].

Abstract

The construction of urban wastewater treatment facilities in Liaoning Province in China is currently developing rapidly； however， there have been fewer studies conducted on the carbon emissions generated by the wastewater treatment system. By utilizing data from a wastewater plant in Shenyang City and referring to the IPCC 2006 Guidelines for National Greenhouse Gas Inventories 2019 Revision and the Technical Guidelines for Carbon Accounting and Emission Reduction Pathways in Urban Water Systems， this study accounts for the carbon emissions from three segments： wastewater conveyance， wastewater treatment， and sludge disposal. Additionally， it analyzes the influencing factors of carbon emissions at this particular plant， which will aid in implementing region-specific measures to reduce carbon emissions. The results showed that the annual carbon emission of a wastewater treatment plant in Shenyang City was 52 450 t. The main factors contributing to this emission were power consumption （39.2%）， the use of polymeric aluminum chloride （18.7%）， and N₂O emissions caused by the wastewater treatment （14.5%）. By using Sumo software package to analyze the key parameters for reducing carbon emissions in the wastewater treatment plant， it was concluded that dissolved oxygen levels could be reduced from the original 6.51 mg·L^-1 to 1-2 mg·L^-1. Additionally， by reducing the dosage of polymeric aluminum chloride to 76% of its original amount， it was possible to reduce the water plant's carbon emissions by 2 230 t. The annual consumption of sodium acetate could be reduced from 3 710 t to 2 672 t， and the carbon emissions were reduced by 28.14% compared to the original levels. Based on the carbon emission accounting results of the plant， the following feasible paths for emission reduction were proposed： optimizing aeration equipment and pumping units to reduce power consumption； introducing precise dosing equipment to minimize pharmaceutical usage； reducing stockpiling time for residual sludge in the plant； employing appropriate methods for recovering phosphorus， macromolecules， and other resources from wastewater and sludge； and utilizing water source heat pump technology for exchanging heat energy in wastewater treatment plant effluent. This research is of great significance to put forward a strategy suitable for the low-carbon operation of the urban wastewater treatment industry in Liaoning.