Physical And Chemical Separation Of High Ammonia Nitrogen From Landfill Leachate And Preliminary Study On Subsequent Biological Treatment

A large amount of landfill leachate produced in the process of garbage stacking and landfill is a typical high ammonia nitrogen refractory sewage with high ammonia nitrogen content,complex water quality and large fluctuation.If it is not treated properly,it will lead to deterioration of water environment,harm water ecology,and cause sharp decline or even totally loss of water function.Aiming at the deamination of ammmonia from the aged landfill leachate,we take the landfill leachate from the equalization tank of Hongmiaoling landfill in Fuzhou for research,and the combined process of dynamic wave stripping as enhanced pretreatment,Fenton oxidation and A/O SBR biological treatment is adopted.According to the results,the treatment effect and the corresponding mechanism were discussed.?1?A experiment on stripping of ammonia from aged-landfill leachate was carried out by dynamic wave stripping technology.In this study,the effects of stripping time,p H,gas-liquid ratio,temperature and concentration of influent ammonia nitrogen concentration on stripping efficiency were investigated.The results of the single factor experiment showed that the stripping removal rate increased rapidly in the first 3 hours,and changed little after5 hours.The proportion of free ammonia increases at high p H,which is more beneficial for stripping,and the most economical when the p H is around 10.5.The applicable temperature of dynamic wave stripping was in a wide range,the removel efficiency could up to 72.62%and 90.68%at 10?and 25?,respectively.The stripping efficiency can be improved by increasing the gas-liquid ratio,but when it was above 129,the increase of gas-liquid specific stripping effect was not obvious.The concentration of influent ammonia nitrogen concentration within the examined range had no significant effect on ammonia stripping.?2?The results of dynamic wave stripping orthogonal test demonstrated that temperature has the most significant effect on the power wave blowing off ammonia.p H and gas-liquid ratio are important factors.The initial ammonia nitrogen concentration has no significant effect on the stripping efficiency.Mass transfer kinetics study shows that the gas-liquid two-phase contact area of the dynamic wave foam area is large,and the contact surface is constantly updated,thus greatly improving the separation efficiency of ammonia nitrogen and mass transfer.The mechanical model accords with the actual mass transfer process.Under the optimal treatment condition,K_mis 71.33,and the average error e is 6.1%.It has certain prediction function for the actual engineering scale-up test.?3?Through Fenton experiments and single factor analysis experiments,the effect of reaction time,initial p H,Fe²⁺and H₂O₂dosage on the test was studied.It is concluded that the optimum conditions for the treatment of landfill leachate by Fenton oxidation method are as follows:the reaction time is 60 min,the initial p H value is 4,and the Fe²⁺cast amount is 0.04 mol/L,30%,the amount of water treated by the cast amount is 0.25%.The average removal rates of COD and ammonia nitrogen were 69.04%and 12.38%,respectively.Fenton oxidation method can remove refractory organic matters,improve the biodegradability of blow off water,increase the B/C value from 0.16 to more than 0.47,reduce the load and treatment cost of subsequent biological treatment,so that it is beneficial to subsequent biodegradation.?4?Followed by a SBR reactor for treatment,the effects of aeration time,anoxic agitation time,Do and p H on the biological treatment experiments were studied.The experimental study determined the optimal operation mode of A/O type SBR reactor is first anoxic stirring 3 h,then aerobic aeration 8 h and then precipitation 1 h,this operation mode is helpful to the removal of total nitrogen in the system.The experiment also investigated the effect of different dissolved oxygen concentrations and initial p H values on the SBR reactor.When the dissolved oxygen concentration was 3-4 mg/L,the initial p H value was7.5,the removal rates of COD and NH₃-N in the reactor were 84.67%and 77%,respectively.?5?The analysis of technological process and economic benefit showed that the treatment of old landfill leachate by dynamic wave stripping+Fenton oxidation+A/O type SBR could meet the pollution control standard of domestic landfill?GB16889-2008?.Compared with many engineering examples using MBR“double membrane”?NF+RO?,it is more economical,the cost of tons of water is about 45.67 yuan,this process can achieve better treatment effect,and there is further room for optimization,which is economically and technically feasible and has certain engineering application value.