Treatment Of Source-Separated Urine By Shortcut Nitrification And Denitrification

Human urine accounts for only 1%of the volume of domestic sewage,but contributes 80%of the nitrogen and 50%phosphorus in domestic sewage.The source-separation and collection of human urine can not only reduce the nitrogen pollution load in domestic sewage,but also realize the recovery of nutrients in the urine.Source-separated urine is characteristized as high pollutant concentration,low carbon/nitrogen ratio(C/N).The traditional biological nitrogen removal process is difficult to deal with.Based on shortcut nitrification-denitrification technology,this paper aims to produce an effluent suitable for anammox process and high-efficiency nitrogen removal.The paper investigated the effects of operating parameters,activated sludge properties and different carbon sources on shortcut nitrification-denitrification biological nitrogen removal efficiency of source-separated urine.The following research results were obtained:(1)For 1:1 dilution of urine,partial nitrification and denitrification were achieved in the SBR.Using organic matter in the urine,about 40%of total nitrogen removal can be achieved,and 55%of the remaining ammonia nitrogen can be oxidized to nitrite.The COD and NH4+-N loads of SBR were 3.23 kg COD/(m3·d)and 1.86 kg N/(m3·d).The NO2--N/NH4+-N ratio in effluent of the SBR was 1.24±0.13,which can be used as the inflluent of the anammox reactor.(2)Granular sludge with the particle size ranging from 100-1000 ?m and excellent settling performance(SVI48-50 mL/g)was established in the SBR.The maximum sludge concentration of SBR was 9.5 g/L.The reactor had excellent ability to fluctuating influent load.(3)For non-diluted urine,shortcut nitrification and denitrification was achieved by double inhibition of high free ammonia and high free nitrous acid in anoxic/aerobic MBR.The 60%total nitrogen of the effluent was removed and the NO2--N/NH4+-N ratio of the effluent was 1.18±0.15.(4)The MBR had a total nitrogen removal rate of over 90%by adding different types of carbon sources.The C/N of methanol and volatile fatty acids were 3.0-3.6 and 2.8-3.0,respectively.Under these conditions,the denitrification rates were 12.87 and 16.34 mg NO2--N/(g VSS·h),respectively.(5)In SBR and MBR,Nitrosomonadales was the dominant aerobic ammonia oxidizing genus.The growth of nitrous acid oxidizing bacteria in activated sludge was inhibited,and it was not detected based on fluorescence in-situ hybridization and high-throughput sequencing technology.The proportion of denitrifying bacteria Pseudomonas in the SBR was 62.4%.In the MBR,the abundance and diversity of the microbial population increased with the addition of carbon sources.The percentages of the denitrifying genus Pseudomonadales,Burkholderiales and Xanthomonadales were 23.5%,12.4%and 3.2%,respectively.