Modeling Of Greenhouse Gas Emission During The Biological Wastewater Treatment Process And Its Application In Papermaking Industry

The papermaking industry is the main consumer of water in traditional manufacturing industry.Compare with the foreign papermaking industry,papermaking enterprises in China have the characteristics of larger consumption and lower utilization rate.Faced with the fact of lacking of water resources,great environment pressure and the increasingly strict national policy,it is necessary to put forward the study of wastewater treatment process in papermaking industry,and it will lay the roots for exploring the method of energy saving and emission reduction in the future.More than this,it will promote the healthy development of papermaking industry as well.So this study have good practical significance and research prospects.The BSM model is a recognized simulation model in the field of wastewater treatment process from both home and abroad.This article built a greenhouse gas emission model during biological treatment process of wastewater based on BSM1.And then,faced the fact of wastewater treatment process and monitoring in papermaking mill,the necessary modification of the model was carried out,and the modified version of greenhouse gas emission?GHG?model base on papermaking industry was carried out.First of all,in order to verify the accuracy of the wastewater treatment model in this paper,the standard wastewater influence data suggested in BSM manual was used as model inputs.The data contains three different weather of different load.This model was used to simulate the changes of pollutant concentration in the biological treatment process of wastewater.The simulation results were compared with the reference results in the BSM manual.Results showed that this model can simulate the dynamic changes of pollutants concentration in the biological treatment process of wastewater,and the effluent quality coincide with the reference value in BSM1 manual under the same condition.It proved that the model have a good accuracy.At the same time,the model was divided into three stage:static simulation,dynamic simulation and test stage.In the test phase,simple dissolved oxygen PID controller,simple nitrate-internal reflux PID controller were added to simulate the simple process control in the treatment process of wastewater.On the basis of the simulation model,a calculation model of GHG was added,and the direct GHG emission was calculated from four aspects of endogenous decay,BOD removal,nitrification process and denitrification process.Thus,model of GHG emission during biological treatment process of wastewater was built.Under the condition of open loop control,we used dry weather data as model input,result showed that the average GHG emission of the four aspects were as follow:0.089 kg CO₂/m³ wastewater?0.177 kg CO₂/m³wastewater?0.165 kg-CO₂/m³ wastewater?0.059 kg CO₂/m³ wastewater,and the total GHG emission was 0.16 kg CO₂/m³ wastewater.Under the same simulate condition,the GHG emission bias when different weather data were used as inputs.When the Dry,Rain,Storm weather data were use as model inputs,the average GHG emission were 123.2 kg CO₂/h,121.5 kg CO₂/h,126.1 kg CO₂/h separately.When using the same data as model inputs,open loop and close loop control do not seem to have a great impact on direct GHG emission.But the electricity consumption can be reduced under close loop control,as well as the indirect GHG emission because of the reduction of electricity consumption.Thirdly,in order to apply the direct GHG emission model to the papermaking industry,this paper made some necessary modification to the model.Then this paper obtained wastewater data from paper mill,and these data were used as inputs to simulate the changes of the pollutant concentration during the biological treatment process of papermaking industry.Result showed that the microbial activity in the treatment system was not high,because of the shortage of nutrients in papermaking wastewater.Not only that,because the concentration of the inert organic particulate matter in the solution was high,it made its concentration increased obviously in the reactor.Seen from the effluent data,this model has a good treatment effect on biodegradable organic matters,the concentration of solute biodegradable organic matters and particulate biodegradable matter decreased from average value of 96.7mg/L and 107.3 mg/L in the inputs into 1.4 mg/L and 0.1 mg/L in the effluent.The direct GHG emission of the treatment process were calculated from two aspects which were endogenous decay and BOD removal.The average direct GHG emission in these two aspects were 0.084 kg CO₂/m³ wastewater,0.121 kg CO₂/m³ wastewater respectively.Among them,the direct GHG emissions by BOD removal accounted for 59%in the total emission.