Research On Rapid Start-up And Stable Operation Of Dairy Wastewater Anaerobic Reactor

With the improvement of living standards,the dairy industry has developed rapidly,and a large amount of wastewater has been generated in the process of dairy processing.Dairy product processing wastewater is generally regarded as one of the important sources of industrial food wastewater.Dairy wastewater treatment usually uses a combination of anaerobic and aerobic processes.Dairy wastewater is rich in organic matter with low specific gravity such as protein,fat oil.etc,which has the problems of unstable anaerobic treatment effect,and easy to run mud.The granular sludge has good settling properties,maintains a high microorganismconcentration in the reactor,and improves the reactor's ability to resist impact loads.Quickly starting the reactor and cultivating anaerobic granular sludge,and at the same time mastering the law of stable operation of dairy wastewater,is of great significance for the startup and efficient and stable operation of dairy wastewater anaerobic reactorIn this study,the starting characteristics of the dairy wastewater anaerobic reactor,the formation of granular sludge,and the stable operating conditions of the react or were studied.The main research contents and conclusions are as follows1)In order to quickly start the anaerobic reactor,this experiment used to improve the mass transfer of the reactor,adding an external circulation device outside the reactor and an internal circulation device inside the reactor;pre-treating the inoculated mud outside the reactor;using high-concentration wastewater Stimulate the measures to activate the inoculated sludge and start the anaerobic reactor.As a result,the 30d start-up operation realized the rapid start-up of the reactor.Reached the design volume load of 11.2 kg COD·m-3·d-1,the chemical oxygen demand(COD)removal rate and gas production remained stable,the COD removal rate reached more than 85%,and the gas production rate was stable at 0.42 m3·kg-1·COD-1·d-1,the inlet water alkalinity(ALK)is kept at about 3100 mg·L-1,the outlet water ALK is always greater than the inlet water ALK,the volatile fatty acid(VFA)is stable at about 50 mg·L-1,and the redox potential(ORP)Always keep below-400mV,the pH is stable at 6.8?7.22)After 30 days of start-up operation,the anaerobic reactor successfully cultivated granular sludge.The anaerobic reactor found that the proportion of granular sludge with a particle size of 0.9?2 mm reached 13.6%,and that of granular sludge with a particle size of 0.71?0.9 mm reached 11%,with a particle size of 0.58?0.71 mm reaches 9.2%,the proportion of granular sludge with a particle sizeof 0.2?0.58 mm reaches 24.8%,and the proportion of granular sludge with a particlesize of 0.2?2 mm reaches 58.6%.The average sedimentation velocity of the particles reaches 64 m·h-1,and the maximum sedimentation velocity reaches 96m·h-1,the ratio of VSS·TSS-1 reaches 71.5%.The colorof granular sludge is grayish brown,mostly spherical or ellipsoidal,with good compactness.Observed by microscope,there are fewer filamentous bacteria on the surface of granular sludge,which is similar to the shape of granular sludge reported by many researchers3)The influence of the load on the reactor operation during the operation of the reactor was explored.It was found that the critical volume load for the stable operation of the reactor was 14 kg COD·m-3·d-1(hydraulic residence time 5.1 h).At this time,the sludge load was 1 kg COD·kgVSS-1·d-1.Critical load,abnormal reactor Deration.If the effluent ALK is less than the influent ALK;the gas production decreases from 332 L·d-1 to 152 L·d-1;the COD removal rate decreases from 84% to 38%;the average sedimentation rate decreases from 68m·h-1 to 42 m·h-1;VFA increased from 114 mg·L-1 to 605 mg·L-1.4)The effect of the amount of mud on the reactor during the operation of the reactor was explored.It was found that the amount of sludge in the reactor during stable operation should be less than 29.4 g·TSS·L-1(about 1/2 of the reactor volume).When the reactor sludge volume reached 29.4 g·TSS·L-1.the reactor operated abnormally.If the effluent ALK is less than the influent ALK;the gas production decreases from 228 L·d-1 to 78 L·d-1;the COD removal rate decreases from 80%to 24%;the average sedimentation rate decreases from 64 m·h-1 to 32 m·h-1;VFA increased from 50 mg·L-1 to 701 mg·L-1.At the same time,the surface of thegranular sludge is covered with filamentous bacteria,which is milky white,and the system appears muddy.By draining the mud,the mud volume was adjusted down to 19.2 g·TS S·L-1(about 1/3 of the reactor volume).After 20 days of operation,the reactor gradually returned to normal.It shows that the amount of mud that can operate normally.in the reactor should be less than 29.4 g·TSS·L-1.