Study On Removal Efficiency And Influence Factors Of Ammonia Nitrogen In Coking Wastewater

Coking wastewater is a kind of industrial waste water which contains high concentration, difficult biodegradation organics and causes serious pollution to the water environment.At present, the coking wastewater treatment technologies at home and abroad widespread exist some problems,such as:effluent effect is not good,system is not stable, processing cost is high. According to the high ammonia nitrogen content(3500mg/L) in coking wastewater, the chemical precipitation method was used to remove ammonia nitrogen as pretreatment in this study and its influence factors are analyzed. On this basis, A/O process was used for wastewater biological treatment, research results provide certain reference for coking wastewater treatment technology and wastewater comprehensive discharging standard, have certain theoretical significance and application value.Research results show that:(1)The ammonia nitrogen removal rate of aeration is61%, ammonia nitrogen content reduced from3500mg/L to1365mg/L.(2)Chemical precipitation reactions is affected by the initial concentration of ammonia nitrogen, with the increase of ammonia nitrogen, ammonia nitrogen removal rate increased.(3)Reaction effect has a big relationship with precipitation agent,best precipitation agent are Na2HPO4·12H2O and MgCl2-6H2O.(4) Best dosing ratio:n (MgCl2·6H2O):n (NH4+):n (Na2HPO4·12H2O)=1.3:1:0.9.(5)With different dosing sequence, reaction effect is different,the best dosing sequence is dosing Na2HPO4·12H2O first and then MgCl2-6H2O.(6)Best conditions of chemical precipitation reaction:pH=10,T=30℃,r=200r/min, reaction time is10minutes.Under these best conditions,the ammonia nitrogen removal rate is93.4%and ammonia nitrogen content is reduced from3500mg/L to231mg/L.(7)The effluent of pretreatment was treated by A/O process, ammonia nitrogen removal rate is60.10%, phenol removal rate is91.66%,the ammonia nitrogen and phenol content of effluent is45.99mg/L and8.24mg/L.(8)The biological process effluent after coagulation sedimentation treatment, ammonia nitrogen content reduced to17.3mg/L,phenol content reduced to5.2mg/L, COD content reduced to143mg/L.