Carbon Emission Calculation And Prediction For A Petrochemical Wastewater Treatment Plant

Extreme weather and global warming have been the subject of much attention,and with carbon emissions increasing year on year,the dangers of carbon emissions and the importance of carbon reduction are gaining more and more attention.With the development of the low carbon economy and the proposed“carbon peaking and carbon neutralization”background,environmental carbon reduction will be a hot topic in the coming decades.As one of the industries with high energy consumption and high carbon emissions,accounting carbon accurately is an important prerequisite for the implementation of carbon reduction in wastewater treatment plants.In order to understand the current carbon emission status of Chinese wastewater treatment industry and to grasp the methods and models for accounting for carbon emissions from wastewater treatment plants,and then to explore their energy saving and greenhouse gas reduction measures,the following work has been carried out in this paper.This paper selects a petrochemical wastewater treatment plant as a case study,and uses material balance algorithm and carbon footprint method to calculate the carbon emission of it after studying the carbon emission calculation methods and models of various wastewater treatment plants.The material balance algorithm firstly tracked the C element in the biochemical system,and analyzed the removal way and removal amount of the chemical oxygen demand,which entering the wastewater treatment system.Secondly,the CO₂ and CH₄ produced in the process of sludge landfill disposal were analyzed and calculated.Then the material consumption of the main unit of the wastewater treatment plant was calculated,it included the statistics of the type and power of electrical equipment and drug dosage.Finally,the CO₂,CH₄and N₂O produced by the sewage treatment plant were calculated.The carbon emission（CE）of the case wastewater treatment plant in the basic year was 68587.76 t based on the results of material balance and material consumption balance,after summarizing the different calculation methods of CO₂,CH₄ and N₂O.The main source is the indirect emissions caused by electricity consumption.The results of the material balance of the biochemical system show that most of the chemical oxygen demand entering the wastewater treatment system is removed in the aerobic process,which has a large space for emission reduction.In order to obtain a more accurate carbon footprint of a wastewater plant,a carbon footprint analysis is also required.The carbon footprint is based on the life cycle assessment method to analyze the total carbon footprint（TCF）of the wastewater treatment plants.According to the life cycle assessment steps,the system boundary,emission factors and emission inventory were determined,and the inventory data was collected,then the carbon footprint of the wastewater treatment plant was analyzed.According to the selected system boundary,the TCF of the wastewater treatment plants was composed of four parts.They were energy consumption emission,sewage treatment emission,pharmaceutical and carbon source addition emission,and sludge landfill disposal emission,respectively.The TCF was 124891.46 t/a,among which the release of CH₄ in the process of sewage treatment and indirect emissions caused by energy consumption were the main sources of carbon emissions.The results of this calculation were used as the base data to construct a model for carbon emissions projections.After obtaining the base carbon emission data of the wastewater treatment plant in 2021,the LEAP model combined with the scenario analysis method was used to apply the established carbon emission prediction model to the case wastewater treatment plant to predict its future CE under the baseline scenario,low emission reduction scenario,medium emission reduction scenario and high emission reduction scenario.The results of the prediction were:the CE from the wastewater treatment plants tended to increase each year under both the baseline and low reduction scenarios,with CE increasing by 118%and 75%in 2060,respectively.The CE under the medium reduction scenario showed an increase followed by a decrease,with a peak point in 2025,followed by a decrease of 45%in 2060 approximately.And CE from the wastewater treatment plants under the high reduction scenario showed a sharp reduction,decreasing to 2050 followed by a slight increase,with emissions decreasing by 92%in 2060 approximately.This has implications for the future implementation of carbon emission reductions from wastewater treatment plants.