The Preparation Of Aerobic Granules And Its Application On The Trestment Of Food Wastewater

Aerobic granular sludge is a bioaccumulator formed by the interaction between microorganisms.It has the dense structure,the good settlement performance,the strong capacity to suffer the fluctuation of organic loading and toxic environments.However,aerobic granules are easy to crack and hard to domesticate in a short time.The seed sludge,substrate composition,pH,temperature and reactor operating conditions also have an impact on the preparation of granules.Therefore,this work focused on the effect of COD,hydraulic shear,reactor structures on the preparation process.In addition,the application of aerobic granular sludge on the practical wastewater had been investigated and the food wastewater was selected as a modle.In the cylinder SBR,anaerobic activated sludge was successfully inoculated to cultivate the mature aerobic granular sludge during 36 days with the MLSS of 4622 mg·L-1 and the SVI of 52 mL·g-1.The removal rates of COD and ammonia were 97%and 86.5%,respectively.Compared with the baffle reactor,the cylinder reactor provided greater hydraulic shear force and the faster sludge granulation rate.The granular sludge was more compact and dense.In addition,the reduce of settling time would optimize the settlement performance of the sludge.The food wastewater played a positive role to the wastewater treatment capacity and stability of aerobic granular sludge.The optimal C/N value was measured to be 5 for the treatment of food wastewater.To degradate the food wastewater,COD values were gradually raised in the inflow.Paracoccus and Thauera were the two dominant flora in this process.The removal efficiency of COD,TP,ammonia nitrogen and TN were 92%,86.6%,96%and 87%,respectively.With the increase of COD values,the rate of sludge granulation and the degradation rate of pollutants were enhanced,while the production of EPS were also increasing and the physical properties of granules became more stability.In addition,with the addition of food wastewater,the dominant species were enriched when the biodiversity reduced.At the family level,the abundance of Rhodocycaeaceae increased gradually and the abundance of Rhodocyclaceae decreased,when the COD was 2000 mg·L-1,the aerobic granular sludge was unstable.Comamonadaceae and Pseudomonadaceae became the dominant flora.Then Rhodocyclaceae,which can digest a variety of organic matter in the sample,became the main strain,Flavobacteriaceae following.In this process,some new microbes appeared,such as Trueperaceae,Anaerolineaceae,Xanthomonadaceae.Anaerolineaceae became the dominant species in the condition of high COD concentrations and high proportion of food wastewater.At the same time,as the food wastewater contains a large number of ester compounds,Flavobacteriaceae,which could degradated them well,becomed the second largest dominant bacteria.The results of this study are as follows:1)The mature aerobic granular sludge with the high stability and 0.8-1.0 mm particle size was prepared rapidly.The role of hydraulic shear force and EPS are clarified.2)The degradation of food wastewater was completed efficiently by aerobic granular sludge and the effects of food wastewater,C/N,and COD on the microbial flora were studied.3)The minimum COD concentration which aerobic granular sludge could suffer was studied to be 300 mg·L-1.