Application Of Short-cut Nitrification Of Zeolite Aerated Biological Filter In Biological Denitrification Of Landfill Leachate

Aged landfill leachate is a typical wastewater with low C/N ratio and high concentration of ammonia nitrogen.Short-cut nitrification-denitrification process is more energy-saving,consumption-reducing and emission-reducing than traditional biological denitrification process for treating low carbon-nitrogen ratio wastewater.Based on an actual leachate treatment project in Guangzhou,this paper took the short-cut nitrification of zeolite biological aerated filter(ZBAF)as a main research object to explore the start-up and continuous operational characteristics of ZBAF in both aspects of lab-scale and full-scale.Besides,effects of salinity,influent nitrogen loading rate(NLR)and organic carbon on the short-cut nitrification performance of ZBAF were all investigated to evaluate the stability of short-cut nitrification performance and shock resistance ability of ZBAF.Moreover,the synergistic effect between two-stage A/O and ZBAF was discussed as well.It took just 10 days for ZBAF to start up by controlling the free ammonia(FA)in the reactor higher than 3.1 mg/L and lower than 10.0 mg/L,which led to an intensive inhibition of the nitrite oxidizing bacteria(NOB)rather than the ammonia oxidizing bacteria(AOB).Short-cut nitrification could be successfully achieved within 21 days.Ammonia nitrogen removal rate(ARE)higher than 80.0%,nitrite nitrogen accumulation rate(NAR)higher than98.0%and nitrite production rate(NPR)as 1.356 kg N/m~3/d were got respectively.The results of high-throughput sequencing showed that NOB was completely inhibited and the relative abundance of AOB was significantly higher than that of inoculated sludge after stable short-cut nitrification successfully established in ZBAF.The hydraulic retention time(HRT)was reduced from 4.0 h to 3.5 h,with NLR increasing from 1.500 kg N/m~3/d to 1.714 kg N/m~3/d,which promoted the growth of NPR from about 1.230 kg N/m~3/d to about 1.350 kg N/m~3/d.On the contrary,by shortening HRT from 3.5 h to 3.2 h in order to get a higher NLR of 1.875 kg N/m~3/d,the NPR of ZBAF fell back to about 0.995 kg N/m~3/d.The effect of salt on biochenmistry was studied experimentally.With the increase of NaCl dosage from 0 g/L to25.0 g/L in influent,ARE decreased from more than 80.0%to 34.7%,and NPR reduced from1.356 kgN/m~3/d to 0.600 kgN/m~3/d.However,ZBAF did not collapse when suffering from salt stress,indicating that ZBAF was feasible to treat wastewater containing both ammonia nitrogen and high level salinity.The results of high-throughput sequencing likewise revealed that the addition of NaCl would resulted in the decrease of the relative abundance of AOB.The debugging and operation of 25 m~3/d full-scale ZBAF showed that ZBAF had outstanding stability and recovering ability.Stable short-cut nitrification was achieved by FA control on the 28th day and startup of ZBAF was complete.When the inflow rate was 2.8times the design flow rate as 2.92 m~3/h,with NLR as about 2.400 kgN/m~3/d,the ARE of ZBAF was about 65.0%and the NAR was above 80.0%,with a NPR of about 1.342kgN/m~3/d.It was efficient to bring ZBAF back alive by taking smaller inflow or stopping inflow to turn it into stifling aeration when the short-cut nitrification performance of ZBAF became worse attributing to nitrogen loading shock.Besides,it proved out that biodegradable organic carbon and salt stress in landfill leachate would deteriorate the short-cut nitrification performance of ZBAF.Furtherly,the synergistic effect between ZBAF and two-stage A/O was found.