Research On Performance And Mechanism Of A/O-MBR+O₃ Lysis Combined System For Sludge Reduction And Enchanced Nitrogen Removal

Anoxia/aerobic membrane bioreactor?A/O-MBR?is an emerging wastewater treatment process,which combined traditional A/O activated sludge process and membrane separation technology.A/O-MBR has advantages of simple structure,small footprint and high automation,etc.But some problems such as limited sludge reduction and denitrification performance still need further improvement.Aiming at the problems of A/O-MBR,O₃ lysis-cryptic growth technology was applied to the A/O-MBR process in this research.A new A/O-MBR+O₃ lysis combined system was developed with synchronous sludge reduction and efficient denitrification.This research mainly investigated the influence of ozone lysis on characteristics of sludge.In addition,evaluated the performance of sludge reduction and wastewater treatment of A/O-MBR+O₃ lysis combined system.Meanwhile,the mechanism of enhanced nitrogen removal of A/O-MBR+O₃ lysis combined system was proposed.During the sludge ozonation,it was demonstrated that the inlet ozone concentration,ozone dosage and operation mode of ozone-lysis-sludge reactor were the key factors influencing the efficiency of sludge lysis.The sludge lysis ratio was23.3±1.4%when the inlet ozone concentration and ozone concentration were set at57.9 mg/L and 66.0 mgO₃/gSS under continuous operation condition.The characteristics of sludge changed after ozonation obviously.The MLSS decreased from 5986±274 mg/L to 4471±169 mg/L.The p H of sludge mixture decreased from 6.9±0.1 to 5.7±0.1.The settleability of sludge was improved and its specific surface area became larger.Besides,the activity of sludge decreased significantly during ozonation.The COD concentration in supernatant of sludge increased from31.2±4.5 mg/L to 1510.2±95.3 mg/L.The TN concentration in supernatant of sludge increased from 5.1±0.3 mg/L to 121.6±9.8 mg/L,among which organic nitrogen accounted for 68.0%,the TP concentration in supernatant of sludge increased from 0.7±0.1 mg/L to 34.7±1.4 mg/L,and 95.1%of TP was PO₄^3--P.The contents of protein,polysaccharide and VFAs in supernatant of sludge increased with different degrees during ozonation.The content and distribution of phosphorus forms in sludge changed a little during ozonation.Nearly 83.8%of TP in ozonized sludge supernatant came from IP in the sewage sludge solid.The TP in ozonized sludge supernatant could be effectively removed by magnesium ammonium phosphate method.The removal efficiency of TP in ozonized sludge supernatant was 51.6%under optimal condition.During operation of A/O-MBR+O₃ lysis combined system,it was demonstrated that the sludge production in A/O-MBR+O₃ lysis combined system was reduced by48.4%compared with that obtained in A/O-MBR.The efficiency of sludge reduction was significant.The removal efficiencies of COD?NH₄⁺-N?TN and TP in A/O-MBR+O₃ lysis combined system were 91.9%?97.2%?79.9%and 19.0%,respectively.After treatment by the combined system,the TN discharge rate of A/O-MBR+O₃ lysis combined system was only 28.5%,which was lower than that of A/O-MBR?42.1%?.The above results indicated that the backflow of ozonized excess sludge could enhance TN removal of A/O-MBR+O₃ lysis combined system.Up to 96.9%of TP in effluent of A/O-MBR+O₃ lysis combined system was PO₄^3--P,which could be removed by adding PAC.Under optimal condition,the TP concentration in effluent was 0.41±0.05 mg/L after phosphorus removal,meeting the first class A of the "National sewage treatment plant pollutant discharge standard"?GB18918-2002?.The mechanism of the enhanced nitrogen removal of A/O-MBR+O₃ lysis combined system was proposed.The SOUR and denitrification rate of sludge in A/O-MBR+O₃ lysis combined system were elevated by 13.8%and 20.8%,respectively,compared with those in A/O-MBR.It is beneficial for degradation of organic matter and TN in ozonized sludge mixture by microorganism in the combined system.The SMP and EPS concentrations in A/O-MBR+O₃ lysis combined system increased by 7.3%and 10.9%,respectively,compared with those in A/O-MBR.It is beneficial for enhancing nitrogen removal from the combined system.A certain amount of residual carbon source was found in ozon ized sludge supernatant,and its recycle could strengthen the denitrification efficiency of the combined process.The relative abundance of genuses related to nitrogen removal in A/O-MBR+O₃ lysis combined system were higher than those in A/O-MBR.For example,Haliangium?Dechloromonas?Ferruginibacter?Thermomonas and Flavobacterium,It is a guarantee for enhancing nitrogen removal in combined system in terms of microbiology.In conclusion,The A/O-MBR+O₃ lysis combined system realized sludge reduction in situ and high efficiency nitrogen removal from wastewater simultaneously.It was of great significance for the resource utilization of sludge,and the promotion and application of A/O-MBR.