Comparative Analysis of Greenhouse Gas Emissions from Domestic Wastewater Treatment Processes by Modeling: Existing Estimation Methods vs Modeling

Abstract

This study examined the existing methodologies and the applicability of process modeling concerning the estimation of nitrous oxide (N<sub>2</sub>O) emissions from wastewater treatment processes. The method of extimating N<sub>2</sub>O emissions from wastewater occurring during biological nitrification and denitrification processes can be divided into those before and after legal nitrogen effluent quality enhancement for domestic wastewater treatment plant. Initial IPCC guidelines such as IPCC 1996 GL, GPG 2000, and IPCC 2006 GL, provided methods for estimating N<sub>2</sub>O emissions throughout domestic wastewater, while the revised version, IPCC 2019 RF, proposed methods for estimating each N<sub>2</sub>O emission by distinguishing wastewater treatment and effluent after the advancement of wastewater treatment plants. The National Greenhouse Gas Inventory Report (NIR) in Korea adopted the methodology of GPG 2000, and the Emissions Trading System (ETS) applies the estimation method of IPCC 2006 GL in the wastewater treatment plants. This study utilized process modeling to consider the process characteristics and operating conditions of wastewater treatment plants. IPCC, NIR, and ETS estimate N<sub>2</sub>O emissions based on nitrogen behavior activity data and emissions factors. On the other hand, process modeling estimates N<sub>2</sub>O emissions in each unit process of the wastewater treatment plant using a 4-step AOB nitrification/4-step denitrification model and a liquid/gas transfer model. The estimation results of N<sub>2</sub>O emissions from modeling method were compared with the estimation results of IPCC, NIR, and ETS to analyze the suitability of the estimation method. Through this, it was evaluated how appropriate process modeling is for estimating N<sub>2</sub>O emissions in domestic wastewater treatment plants.