| The biological nitrogen removal methods based on the partial nitrification(PN)process plays an important role in the treatment of wastewater containing ammonia nitrogen.In recent years,the related research of PN-D and PN-A in the treatment of medium and low concentration ammonia nitrogen wastewater has been relatively mature,but the problem of difficult oxidation of ammonia nitrogen still exists in the treatment of high concentration ammonia nitrogen wastewater(above 1000 mg/L).This is mainly due to the inhibition of high concentration of free ammonia(FA)on ammonia oxidizing bacteria(AOB).Therefore,eliminating or buffering the inhibition of FA is the key for efficient treatment of such wastewater by partial nitrification.In this paper,natural and modified zeolite was added to buffer the inhibition of FA on AOB,and the ammonia nitrogen removal efficiency of partial nitrification was enhanced.the partial nitrification process could be started rapidly under the conditions of high ammonia nitrogen concentration and high load at the same time.it was found that the buffer effect of natural zeolite was similar to that of modified zeolite under the long-term use condition,and the feasibility value of natural zeolite in engineering application was determined.And the efficient and stable nitrogen removal treatment of a practical high-concentration ammonia nitrogen wastewater(copper-ammonia wastewater)by the partial nitrification and denitrification process is realized under the strengthening of the natural zeolite.Through analysis,it is found that natural zeolite can maintain the buffer inhibition effect for a long time under the action of in-situ biological regeneration,and no need of frequent replacement.Firstly,the characteristics of the zeolites were characterized by XRD,SEM and EDS,and the effects of particle size,initial ammonia concentration,addition amount and wastewater type on the saturated adsorption capacity of the two zeolites were investigated.Pseudo-first order kinetic,Elovich kinetic and internal diffusion models were used to analyze the ammonia nitrogen adsorption characteristics of two zeolites.The analysis results showed that the composition type of natural zeolite was mainly clinoptilolite,and the type and mode of ammonia nitrogen adsorption on zeolite were not changed by Na Cl modification.The three factors of particle size,ammonia concentration,and addition had significant effects on the saturated adsorption capacity of natural and modified zeolites(P<0.05),but the type of wastewater had no significant effect on the saturated adsorption capacity of natural and modified zeolites(P>0.05).The saturated adsorption capacity of modified zeolite was significantly higher than that of natural zeolite(P<0.05).In order to explore the differences of strengthening effects between natural and modified zeolites,SBR 1(without adding zeolite),SBR 2(with adding natural zeolite)and SBR 3(with adding modified zeolite)were started under the conditions of influent ammonia nitrogen concentration and load of 500 mg/L and 0.5 kg/(m3·d),respectively,gradually improve the influent concentration and load of ammonia The analysis results showed that the addition of zeolite could effectively alleviate the ammonia oxidation inhibition of FA on Nitrosomonas,and the average ammonia nitrogen removal rates of the three reactors in the first nine days startup stage were 39.4%,74.3%and 75.8%,respectively.SBR 1 showed rapid recovery of partial nitrification after the addition of an equal amount of natural zeolite on the 9th day,indicating that the inhibition of AOB by FA was reversible,and further proving that the zeolite had a buffer inhibition effect.Based on the analysis results of SMP,EPS and microbial community structure succession,it was concluded that the enhanced effect of modified zeolite on partial nitrification was greater than that of natural zeolite in the initial stage of startup,but the optimization effect of modified zeolite tended to be similar to that of natural zeolite with the passage of time.From the perspective of engineering application,natural zeolite could meet the enhance purpose.Nitrogen removal from copper-ammonia wastewater was treated by partial nitrification(SBR)+denitrification(UASB)under the enhanced condition of natural zeolite.The results showed that natural zeolite ensured the continuous enhanced effect of partial nitrification through biological regeneration.the treatment load of the partial nitrification reactor still reached 1.105 kg N/(m~3·d)when FA concentration was 73.5mg/L,and the ANR remained above 95%.The saturated adsorption capacity of the natural zeolite is finally stabilized at 11.98 to 12.86 mg/g with a corresponding regeneration rate of 151.7 to 162.8%.The C/N ratio of 2.4 could meet the demand of denitrifying electron donor,and the copper ion in denitrifying effluent was stable under0.1 mg/L.The next-generation sequencing results on Day 140 showed that the predominant species in the SBR were Truepera,Comamonas,and Nitrosomonas with relative abundance of 34.4%,29.9%,and 10.3%,respectively.The main bacterial genera in UASB were Proteiniphilum,Aliidiomarina and Thauera,with relative abundance of 30.2%,7.7%and 6.3%,respectively.In this study,through the zeolite to explore the effective mitigation of FA on microbial ammonia oxidation activity inhibition method,to achieve high concentration of ammonia nitrogen wastewater stable and efficient biological treatment has a certain inspiration. |
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