| With the continuous and rapid development of juice industry,the treatment of high concentration juice wastewater which is of seasonal discharge has gradually attracted people’s attention.Anaerobic digestion is the preferred process for the front-end treatment of juice wastewater.In the actual engineering,there are common problems of anaerobic reactors represented by IC and UASB such as long start-up time,sludge wash-out,acidification,and difficulty in granulation of sludge,while the formation and retention of sludge is the core of the anaerobic reactor.Therefore,it is of great practical significance to explore an anaerobic reactor which can cultivate and retain granular sludge.In this dissertation,a self-developed cyclone anaerobic reactor(invention patent application number:201711183885.3)was adopted to treat the juice wastewater.And the operation of anaerobic reactor and the formation of granular sludge were studied in order to provide reference for the actual engineering.The experiment lasted for 120 days.The main contents of the study are as follows:the start-up and load-lifting process of juice wastewater treatment by swirling anaerobic reactor;the influence of changing stirring intensity on wastewater treatment and sludge settling;the influence of changing the influent concentrati under the same load on COD removal rate;particle size distribution of granular sludge and the comparision of sedimentation velocity between the clean water column and the nutrition column.The results showed that:(1)The anaerobic granular sludge was washed out after only 25 days,and the reactor was started-up in the 28th.The COD removal rate was above 90%under the volumetric load of 2kgCOD/(m~3·d).Granular sludge formation time and reactor start-up time were both much faster than ordinary anaerobic reactors.(2)Corresponding measures were taken immediately after the occurrence of acidification on the 47th day in the test.What’s more,after only 9 days,the reactor was restored to normal level and it can operate stably.Which indicated that the reactor have strong ability of acidification remission.(3)On the 91th day of the test,the reactor volume load was increased to about 9.6kgCOD/(m~3·d),and the COD removal rate was maintained at about 86%,with the COD of effluent being reduced to 1120 mg/L,which greatly reduced the difficulty in subsequent treatment.(4)Under the volume load of about 9.6kgCOD/(m~3·d),the rotation speed and the influent concentration were adjusted respectively.And it was found that the combined effect of sludge sedimentation and the organic matter removal effect were best achieved when the rotation speed was 250r/min.The average COD removal rate of the reactor were all above 80%at an influent concentration of about 10000mg/L,8000mg/L and 5000mg/L,indicating that the reactor had a strong ability to adjust the influent of different concentrations.(5)The main particle size of the granular sludge in this test ranged from 1.5 to 2.5mm,with a 41%ratio,and the particle size satisfied the requirements of the granular sludge.Under the state without stir,the particle size distribution of the granular sludge was not uniform.The particle size of granular sludge which were larger than 2.5mm from 1~#sampling port in the reactor accounted for 20%,while the 2~#sampling port only accounted for 4%.Therefore,the significance of intermittent stirring was that the bottom microorganism in the bottom can regain nutrients.(6)The sedimentation velocity of granular sludge in the nutrition column was not consistent since the influence of bubbles,especially for the intermediate particle size had a large change of settling velocity.And the sedimentation velocity difference of the granular sludge of 1.5~2.5mm ranged from-36.96m/h to-6m/h compared with that in the clean water column.Avoiding the influence of bubbles on the sedimentation rate of such sludge would be of great significance for the formation and retention of granular sludge. |
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