Comprehensive Numerical Modeling of Greenhouse Gas Emissions from Water Resource Recovery Facilities

Abstract

A numerical model was developed to comprehensively predict greenhouse gas (GHG) emissions from water resource recovery facilities. An existing activated sludge model was extended to include a nitrifier-denitrification process and carbon dioxide (CO₂) as a state variable. The bioreactor model was coupled to a process-based digester model and an empirical model of indirect CO₂emissions. Direct emissions were approximately 90% of total GHG emissions for a plantwide simulation using the Modified Ludzack-Ettinger process. Biogenic CO₂, nitrous oxide (N₂O), and methane (CH₄) represented 10, 43, and 34% of total emissions. Simulating a dissolved oxygen controlled closed-loop system reduced both sensitivity and uncertainty of GHG emissions. Nitrous oxide emissions were much more sensitive under different design and operating conditions compared to CH₄and CO₂, indicating a significant mitigation potential. An uncertainty analysis found that the uncertainty in GHGs emissions estimates could be significant. Nitrous oxide emissions dominated in both magnitude and uncertainty.

Optimization of wastewater treatment plant operation for greenhouse gas mitigation

“…2.0 mg/L). This is because according to the results described in Kim et al (2015), the effects of DO concentration on GHG emissions were extremely significant in the first aerobic reactor due to its much more favorable environment for N 2 O emission by ammonia-oxidizing bacteria (AOB).…”

“…This work relies on a numerical model that simulates plant operation, and predicts both direct and indirect emissions of CO 2 , N 2 O and CH 4 . The numerical model was presented and explained in detail in previous studies (Kim, 2014;Kim et al, 2015).…”

Greenhouse gases from wastewater treatment — A review of modelling tools

“…Over the years, several approaches have been described to understand GHG production processes (e.g., Foley et al, 2010;Daelman et al, 2012), quantify and measure GHG emissions (GWRC, 2011;Pan et al, 2012Pan et al, , 2013Peng et al, 2014) and predict and control their production (Flores-Alsina et al, 2011b;Corominas et al, 2012;Ni et al, 2013aNi et al, , 2013bKim et al, 2015a). Although GHG emissions from WWTPs are currently an area of concern, the source and magnitude (mainly for N 2 O) are relatively unknown, and the body of knowledge is still incomplete (Kampschreur et al, 2009, Law et al, 2012aPeng et al, 2014), although attention must be placed on long-lived carbon (e.g., due to any oxidation of fossil carbon in WWTPs) and the other GHG.…”

“…Recent studies have demonstrated the paramount importance of applying a plant-wide approach that includes GHG Kim et al, 2015a). A plant-wide modelling approach includes liquid, solid, and gaseous emissions .…”

“…However, despite early efforts towards the integration of established activated sludge models (Henze et al, 2000) with GHG models (Batstone et al, 2002;Hiatt and Grady, 2008;Ni et al, 2013aNi et al, , 2013bMampaey et al, 2013;Guo and Vanrolleghem, 2014), few studies have discussed the benefits (in terms of reducing the GHG emissions coupled with the limitation of other pollutants from WWTPs) of applying GHG model at the plant-wide scale (Gori et al, 2011;Sweetapple et al, 2013;Flores-Alsina et al, 2014;Kim et al, 2015a).…”