The Study Of Hydrolysis And Acidification Of Sludge Enhanced By Ultrasound Coupling Aeration And Agitation As The Carbon Sources Of Denitrifying Phosphorus Removal

The sewage sludge from urban wastewater treatment plant contains rich organic matters and nutrients such as nitrogen,phosphorus.Ultrasonic pretreatment and hydrolysis acidification of sewage sludge can recover the production of dissolved organic matters and hydrolysis product and then used as carbon sources of biological denitrification and phosphorus removal.In order to increase the SCOD in the sludge supernatant after ultrasonic pretreatment and the VFA in the sludge supernatant after hydrolysis acidification,this experiment studied the enhancement of ultrasonic disintegration of sewage sludge by aeration and agitation,the effects of ultrasonic pretreatment conditions,pH,temperature,SRT on the hydrolysis and acidification of the sewage sludge and the feasibility of the production of anaerobic fermentation as the carbon sources of denitrifying phosphorus removal.The followings are the main conclusions:(1)The optimal ultrasonic irradiation density is 0.9W/mL,the optimal aeration flow rate is 20 mL/min,the optimal aeration time is 10 min,and 5min of aeration in later stage is more effective than aeration in whole 10 min.Compared to the same conditions of ultrasonic disintegration of sewage sludge,SCOD of ultrasound with aeration increased by 97.7%,Under the same conditions in SCOD,energy consumption decreased by 25% under ultrasonic conditions with aeration;Experiments manifested agitation as another assistive technology can improve ultrasonic sludge disintegration efficiency at the rotating speed of 600 r/min.Compared to the same conditions of ultrasonic disintegration of sewage sludge,SCOD of ultrasound with aeration and agitation increased by 120.8%,Under the same conditions in SCOD,energy consumption decreased by 12.5% under ultrasonic conditions with aeration and agitation.(2)VFA reached maximum in the first 5 days of hydrolysis and acidification;With the increase of ultrasonic processing time and ultrasonic irradiation density,VFA in sludge of hydrolysis and acidification increased in a certain range,the optimal ultrasonic processing time is 10 min and the optimal ultrasonic irradiation density is 1.5W/mL for hydrolysis and acidification;In alkaline condition the VFA produced by hydrolysis and acidification of sewage sludge can be substantially improved and the best pH is 11 in which causes the highest VFA;Increasing the temperature appropriately is beneficial to the VFA,and the 35? is the optimal temperature for hydrolysis and acidification;With the increase of SRT,VFA of hydrolysis and acidification increased,but the increase is very small,so in this experiment the SRT=9d for sludge fermentation was selected.(3)The SBR reator operated in alternate anaerobic and aerobic condition,after running 30 days,the phosphorus removal rate is above 85%;Then the reator operated in alternate anaerobic,anoxic and aerobic condition,through adding nitrate to induce Denitrifying Phosphate Accumulating Organisms(DPAO),after running 25 days,the DPAO was successfully induced;Adding fermentation liquid can improve the removal rate of phosphate effectively and the removal rate of phosphate is the highest when the adding ratio of fermentation liquid is 1/35 of the wastewater.The system kept operating stably and the removal rate of phosphate has been increasing when added fermentation liquid as the carbon sources of denitrifying phosphorus removal for a long time,and the removal rate of phosphate reached 100% when the system operated beyond 20 days.