Research on establishing a numerical model to calculate greenhouse gas emissions from the domestic wastewater treatment system

Abstract

Calculating greenhouse gas emissions from wastewater treatment systems based on numerical models is a new method in the world. Based on the chemical balance equations of the components, including substrate balance equations, biomass balance equations in reaction tanks, stoichiometric coefficients of substances participating in biochemical reactions in the treatment system. Mathematical equations are solved numerically and coded using the Matlab programming language. Numerical models help calculate and forecast greenhouse gas emissions, evaluate the influence of a number of parameters on the ability to emit greenhouse gases, from which appropriate operating parameters can be selected to ensure efficiency. sustainability of the treatment system.

Applying of numerical model for calculation of domestic wastewater treatment plants at Hanoi Plastic Joint Stock Company achieved the following results: in the case of CH4 gas recovery and combustion, the treatment system with a treatment capacity of 200 m3 /day, greenhouse gas emissions and emission factors are 91.505 kgCO2- eq/day and 2.34 kgCO2-eq/kgBOD. Greenhouse gas emissions from the processing process account for more than 60%, greenhouse gas emissions from electricity production account for nearly 40%. During the treatment process, greenhouse gas emissions are mainly concentrated in biological treatment tanks and anaerobic digestion tanks, accounting for more than 40% in each tank. In the case of CH4 air release, greenhouse gas emissions increase two times compared to the recovery case, specifically the system's greenhouse gas emissions are 186,156 kgCO2-eq/day. Considering a number of factors affecting the system in the case of CH4 gas recovery, the results show that an increase of 1oC increases 3.57 kg CO2-eq, an increase in concentration of 10 mg BOD/l increases 3.13 kg CO2-eq, increasing 1 day of sludge retention increases 13.04 kg CO2-eq in the biological treatment tank, in the anaerobic sludge digestion tank, when increasing 1oC, the decrease is 1.82 kg CO2-eq, increasing the concentration by 10 mg BOD /l increases 4.45 kg CO2-eq, increasing 1 day of sludge retention reduces 7.017 kg CO2-eq.

Keywords: Modeling and calculating greenhouse gas emissions; greenhouse gas emissions; domestic wastewater