Analysis Of Wastewater Characteristics And Optimization Of Coagulation Treatment From Iron And Steel Company In The North

Wastewater is discharged into the sewage treatment plant from the zone of large iron and steel company.The wastewater quantity and quality is different for emitted time and location.The nonlinear spatio-temporal change of emission characteristic is obvious.The existed complex sewage treatment parameters of fixed technological process flow were often appropriate to the quality and quantity fluctuation of operating conditions.It will cause the result that the effluent contained high concentration of pollutants.Therefore,some parameters of the industrial produced water exceed the standards of wastewater reuse,which will be the significant bottleneck for reusing the wastewater of large iron and steel company.Then a lot of sewage was discharged into the river and has a serious effect on the environmental quality.In order to solve this problem,the characteristics of the sewage should be found out from the plant.Based on the existing technology of the plant,it is necessary to change the way of dosing agent and improve the effect of coagulation.In this paper,complex wastewater from a large iron and steel company located in Northeast was considered as the research object.The detail work is as followed:the characteristic of wastewater was analyzed,the rules of time and location of effluent was discussed,the technology process was optimized,and the scheme of coagulation agent dosage was recommended.Moreover,based on the actual operation data of the plant,the quantitative mathematical relationship was found out between the total influent and turbidity of sewage,also pH of sewage flows in regulating reservoir.Then,different sewage turbidity and pH under the optimum coagulant dosage was investigated,and the establishment of water quality complex sewage treatment plant coagulation was founded based on the mathematical model of automatic dosing.The research results of this paper can provide a feasible scheme for the complex sewage utilization of the steel company.The experimental results in this paper are as follows:Effluent of the iron and steel company was collected into three sewage pumping station by separate water pipes.The change of water quality is mainly affected by the discharge of civil sewage.But the concentration of pollutants,such as turbidity,COD and oil,is mainly depended on correlative production engineering.Civil sewage appears as major contributors to the 1#pump station.But it also receives the effluent from two kinds of industrial wastewater.Therefore,the content of COD and suspended solids in water is higher than the other two pumping stations.Meanwhile,this station contributes the most contaminants.In 2#pump station,industrial wastewater is principal components,including cold rolling wastewater and coking wastewater.Therefore,compared with the other two pumping stations,the value of conductivity and hard is higher.The 3#pump station is a typical industrial waste water collector.It is mainly used for receiving the drainage of the blast furnace area and the two cold burning areas in the iron making plant.Therefore,the higher content of oil is obvious feature for 3#pump station.The optimum dosage of Ca?OH?₂,PFS and PAM in the first coagulation process is 100 mg/L,70 mg/L and 0.6 mg/L under the water quality of the complex sewage treatment plant.When the concentration of Ca?OH?₂ is at 100 mg/L,the value of pH is about 8.9,and the removal of hardness is best at this time.After adding Ca?OH?₂ dosage,the removal rate of CODCr increased,which is matched with the dosage of PFS increasing.But the content of Fe2+and PFS in water dosage positively correlated,so we should try to control the dosage of PFS.The order of adding Ca?OH?₂ and PFS dosage has significant effect on the removal of the turbidity,CODCr,NH4-N and conductivity.The results show that the first Ca?OH?₂ coagulation effect is better than the first PFS.Ca?OH?₂ and PFS dosage interval at about 30s,the removal rate of COD reached 56.61%,with the increase of the time interval after dosing.The removal rate of COD increased slowly.And the effect is not obvious.The optimum coagulation conditions of polyferric sulphate:rapid stirring speed 300 rpm,stirring time 1.5 min,slow stirring speed 60 rpm,and slow stirring time 25 min.In addition,the main factors affecting the dosage of coagulant in the regulating pool were analyzed.The results showed that turbidity and pH are the main factors that affect the dosage of coagulant.The difference between the three pumping stations is the main reason for the change of sewage water quality in the regulating pool.This study is based on the historical data of the sewage treatment plant operation comprehensive steel company.Mathematical relationship between turbidity and pH from the three sewage pumping station and regulation pool was determined.Then the results were combined with experimental results,mathematical model is established to regulate water turbidity and pH pool for regulating coagulant process.With established mathematical models,we calculated the data fitting to existing operational data and the model fitting degree,and verified the validity of the mathematical model in practical production process.