Study On Treatment Of Mature Landfill Leachate By Catalytic Ozonation-SNAD Combination Process

Sanitary landfill has become the primary municipal waste treatment method,with the advantages of simple process operation and low investment cost.With the growth of landfill age,a large amount of mature landfill leachate is generated,which poses a severe threat to the ecological environment.Therefore,this paper proposes a catalytic ozonation-simultaneous partial nitrification,Anammox,and denitrification（SNAD）combination process for the characteristics of mature landfill leachate,and systematically studies the treatment efficiency of this combination process for mature landfill leachate and analyzes the mechanism.The details and conclusions are as follows.（1）The optimal operating conditions of the catalytic ozonation process obtained by response surface methodology are as follows:the ozone oxidation time was 115.9 min,the O₃/COD dosing ratio was 1.80,and the catalyst dosage was 248.20 mg/L.The significant relationship between these three factors on COD removal effect was obtained by significance analysis:ozone oxidation time>O₃/COD dosing ratio>catalyst dosage.In addition,characterization of mature landfill leachate at different treatment periods by EEM and LC-MS techniques clearly showed that the refractory organics in mature landfill leachate could be effectively removed in the catalytic ozonation process.（2）The start-up process of the SNAD reactor was investigated and the corresponding mechanism was analyzed.Firstly,the enrichment of AOB was carried out under room temperature conditions with DO controlled in the range of 0.3～0.5 mg/L.The influent water was artificially dosed,and the activity of AOB was finally determined to reach0.219 g/（L·d）by the microbial activity test.At the same time,An AOB was inoculated into the SNAD reactor alone.The anaerobic conditions were controlled,the influent load was gradually increased,and An AOB activity reached 0.153 g/（L·d）finally.After the two strains were successfully cultured separately,AOB was inoculated into the SNAD reactor for the mixed culture of AOB and An AOB,and the culture conditions were continuously optimized.After 30 days of strain mixing,the mixed culture of both strains was effective.Subsequently,glucose was added to the influent to cultivate DNB to improve the COD removal capacity of the reactor,and the final COD removal load reached 0.353 g/（L·d）and total nitrogen removal load reached 0.456 g/（L·d）,and the SNAD reactor started up successfully.（3）A catalytic ozonation-SNAD reactor combination process was constructed to treat mature landfill leachate.The performance of the two treatment units in removing COD and total nitrogen（mainly ammonia nitrogen）was analyzed separately.It was concluded that the average effluent concentrations of total nitrogen,ammonia nitrogen and COD were 21.8 mg/L,12.7 mg/L and 42.3 mg/L,respectively,after the combined process was operated stably,which means that the combined process worked well.The results of the microbial activity test showed that the overall strain activity was at a high level during the whole operation period.The microbial activity reached 0.047 g/（L·h）at the end of the combined process operation.High-throughput sequencing of the bacterial community on the biofilm in the SNAD reactor for different periods showed that the structure of the bacterial community on the biofilm was relatively stable.The dominant genus on the biofilm were Candidatus＿Brocadia,norank＿f＿norank＿o＿SBR1031,norank＿f＿A4b,norank＿f＿JG30-KF-CM45,Limnobacter,Arenimonas Micropruina,Dechloromonas,and Denitratisoma.