Effect of thermal hydrolyzed sludge filtrate as an external carbon source on the performance and microbial community structure of a biological nitrogen removal system
Thermal hydrolyzed sludge filtrate(THSF)can be used as an external carbon source for biological nitrogen removal system,which can improve the efficiency of COD utilization in sludge and achieve the resourceful utilization of sludge.Based on the exploration of the characteristics of THSF obtained at different thermal hydrolysis pretreatment temperatures,the effect of THSF as an external carbon source on the biological nitrogen removal process was investigated by using a lab-scale anaerobic/anoxic/oxic(A2/O)system.The results showed that there was no significant difference in the maximum specific denitrification rate of THSF obtained from different thermal hydrolysis pretreatment temperatures.Under the thermal hydrolysis pretreatment conditions of 165 ℃ and 30 min,the COD and protein dissolution rates in the waste-activated sludge were higher,which could be up to 44.23％and 48.92％,respectively.The THSF obtained from the thermal hydrolysis pretreatment conditions(165 ℃,30 min)used in the actual project was used as the external carbon source for continuous testing.The TN removal efficiency and maximum denitrification rate of the system reached up to 79.62％and 17.55 mg N·(g VSS·h)-1 at 0.6％volumetric addition ratio of the THSF,which were comparable to the denitrification performance when sodium acetate was added.Comparing the microbial community structure when the external carbon source was sodium acetate,the relative abundance of conventional denitrifying bacteria increased to 18.55％after the introduction of THSF,and the relative abundance of denitrifying phosphorus-removing bacteria Dechloromonas increased from 3.04％to 3.72％,which indicated that the THSF could strengthen the coupling between denitrifying process and biological phosphorus-removing process,and then enhance the efficiency of the utilization of organic carbon source.In conclusion,the THSF as an external carbon source can significantly enhance the denitrification performance of A2/O system and strengthen the structure of denitrifying bacterial community,which in turn can achieve the recycling of sludge resources and simultaneously enhance the removal efficiency of wastewater nutrient.
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