Study On The Removal Of Ammonia Nitrogen In Micro-polluted Source Water By Modified Zeolite Biofilter

With economic development in recent years, emissions of some domestic sewage, industrialand aquaculture wastewater result in high concentrations of ammonia in drinking water, whichhave posed a serious threat to human health. In order to improve the water quality and protecthuman health, the removal of ammonia nitrogen in the slightly polluted source water has becomeone of the current hot spot. In the study, the modified zeolite was used as biological carrier of thefilter, and mixed bacteria containing nitrifying and denitrifying bacteria as biological inoculums.After biofilm hung on surface of modified zeolite, the filter could systematically operate to treatsimulated micro-polluted water. The main contents were as follows:Salt (NaCl solution) for modifying the natural zeolite was first performed and then thermallydecomposed to improve its ammonia adsorption performance. The characterization of the naturalzeolite and modified zeolite were analysed by BET, SEM and XRD. The comparison ofammonia adsorption performance of the two zeolites was also studied in paper. The resultsshowed as below: the ammonia removal of modified zeolite was higher when the sodiumchloride concentration was2.0mol/L. After modification, surface morphology structure ofzeolite became more porous, and surface roughness improved greatly. However, the crystalstructure had not been destroyed, with increased sodium content and significantly reducedcalcium content. Under the same condition, the modified zeolite had better ammonia adsorptionperformance than natural zeolite. Modified zeolite was improved the absorption capacity ofammonia, and greatly accelerated the absorption rate of ammonia. The NH4+ion exchangecapacity increased from0.56mg/g to0.79mg/g and the adsorption time reduced from12to4hafter modification.Ammonia, nitrogen and CODMnperformance degradation by the mixed bacteria wasexamined under conditions of aeration and non-aeration. Then, the mixed bacteria wereinoculated in modified zeolite filter. Biofilm formation in different aeration culture methods forammonia removal was investigated. The results indicated that nitrification and denitrificationcould occur simultaneously whether or not in aeration circumstance, nitrification was more likelyto happen in aeration condition, denitrification was favorable to react in nonaeration condition. In the modified zeolite filter biofilm cultures, compared with the full continuous aeration, themodified zeolite biofilter was more conducive to the removal of total nitrogen by intermittentaeration biofilm culture.The influence of hydraulic loading, dissolved oxygen of influent and water temperature onammonia nitrogen and total nitrogen removal were studied. The mechanism of nitrification anddenitrification in the modified zeolite biofilter at different dissolved oxygen level in water weretried to get in the study. The demonstration revealed that it was more conducive to the ammonianitrogen and total nitrogen removal if the biofilter operated condition was hydraulic loading0.9m3/(m2.h), influent water dissolved oxygen4.5to5mg/L, water temperature15to30℃. Whenthe influent dissolved oxygen was around7.0to7.5mg/L, a strong nitration reaction wasoccurred at lower half of filtration column, and nitrification and denitrification were both weakerat the upper half of filtration column. Yet, when the influent dissolved oxygen around4.0to4.5mg/L, a strong nitration reacted at the first half of filtration column, but only a strongdenitrification reaction at the upper half of filtration column.A long-run research and the ability of ammonia removal restoration of the modified zeolitebiofilter were involved in paper. The results showed that in long-run the modified zeolitebiofilter, ammonia removal rate was above95%, total nitrogen removal efficiency was stablyaround80%, and CODMnremoval rate stabilized at about30%with influent ammonia between3.71mg/L and5.46mg/L at room temperature. In4m3/(m2.h) hydraulic shocks through outage2h, the modified zeolite biofilter for the ability of ammonia removal could be good restorationthrough Stoping operation2h.