Study Of Simulation And Optimization On Biochemical Treatment Unit In Refinery Sewage

At present,the main method for the treatment of refinery wastewater is to add other treatment equipment and technology after the biochemical unit,which increases the energy consumption and cost.In this paper,the practical operation of the wastewater treatment process in the first and second treatment plants of refinery wastewater was studied,firstly using Bio Win 5.0 software which based on the ASDM mathematical model to establish two-stage A/O process.The biochemical treatment unit of two stage A/O process was simulated and optimized,and the accuracy of the model,simulation optimization and simulation method was verified by field experiments.Then established the traditional activated sludge process model,Simulated and optimized the biochemical unit of traditional activated sludge process:1?Analyzed the water quality of two stage A/O process and traditional activated sludge process through experiment,detected conventional and specific components of the model by experiment.Determined the sludge concentration(MLSS)in aeration tank by burning method to evaluate the process operation and established the model.Two stage A/O process field sedimentation tank sludge existence phenomenon,through static concentration experiment to correct the two stage A/O process sedimentation tank model.2?Established the two stage A/O process model.Simulated the actual operation of the process and calibrated model,Simulated and optimized the process in which the effluent Chemical Oxygen Demand(COD)and Total Nitrogen(TN)can not reach the standard.The simulation results showed that the dissolved oxygen(DO)concentration of the first stage and the second stage O tank had little effect on the biochemical system,which can be maintained at 2mg/L,and can save energy consumption;In order to ensure the process COD effluent can reach the standard,the sludge concentration(MLSS)of the first A/O tank maintained at about 4000 mg/L,MLSS of the second A/O tank maintained at about 2000 mg/L,at the same time by step-feed,can improve the treatment efficiency of TN,ensure that the process of TN effluent reached the standard.The accuracy of the model and the simulation optimization method are further verified by some experimental results.Because there are some hidden dangers that effluent may can not reache the standard after simulated and optimizated the two stage A/O process of the first treatment plant,transformed and optimizated the process through the simulation,the original process was transformed into a hydrolysis pool + A/O process,and the O tank and sedimentation tank used in parallel,increased the nitrification liquid reflux without adding NaOH solution.The optimal operation scheme of the modified process is selected by simulation,and the process parameters are as follows: The concentration of DO in aerobic aeration tank is keep at 2 mg/L,the MLSS of aeration tank is maintained at 3000~4000 mg/L,and the reflux ratio of nitrification is 100%.Compared with the original process,the removal rate of COD is increased by 2.5%,the removal rate of TN is improved by of 19.6%,and the optimized effect is improved after modification.3?Established the traditional activated sludge process model,simulated the actual operation of the process and calibrated model.Simulated and optimized the process which the effluent COD was unstable,easy to exceed the standard,and the effluent TN can not reach the standard.The simulation results showed that the DO concentration of the first stage and the second stage aeration tank had little effect on the biochemical system,which can be maintained at 2mg/L,and can save energy consumption;In order to ensure the process COD effluent can reach the standard,the MLSS of the first aeration tank maintained at about 6000 mg/L,the MLSS of the second aeration tank maintained at about 2000 mg/L,The effect of TN on the removal efficiency of stepfeed water is smaller,The process optimization can not make effluent TN reach the standard,so it needs to be optimized by simulation.The original process was transformed into A/O process,half of the first stage aeration tank is changed into an anaerobic section,and the sedimentation tank is connected in parallel;Since the fact that the effluent TN can not be effectively removed,the return of nitrification liquid is increased without adding NaOH solution.The optimal operation scheme of the modified process is selected by simulation,and the process parameters are as follows:The concentration of DO in aerobic aeration tank was kept at 2 mg/L,the MLSS of aeration tank should be maintained at 3000~4000 mg/L,and the reflux ratio of nitrification is 100%.Compared with the original process,the removal rate of COD was increased by 3.12%,the removal rate of TN was increased by a factor of 36%,and the optimized effect was obvious.