Research On Treatment Of Livestock Wastewater Based On Double Granular Sludge Technology

With the development of the livestock industry,livestock scale continues to expand.Aquaculture wastewater has brought serious pollution to the natural environment and many adverse effects to human beings.Committed to more efficient treatment of livestock wastewater,the technology of treating livestock wastewater based on anaerobic and aerobic granular sludge has attracted more and more attention.Compared with flocculent activated sludge,granular sludge has better precipitation performance,high microbial abundance,and rich flora.It can greatly increase the organic matter and nitrogen in livestock and poultry farming wastewater.Phosphorus removal effect,to maximize the reduction of pollutants.Therefore,this study proposes the idea of using anaerobic granular sludge and aerobic granular sludge technology to treat livestock wastewater in series,and intends to explore an efficient treatment method for the treatment of livestock wastewater through research.The specific contents of this paper are as follows:（1）The anaerobic granular sludge was cultured in upflow anaerobic sludge bed（UASB）reactor,the granular performance and pollutant removal performance during the cultivation process were investigated,and the parameter optimization of the main granular sludge reactor was studied:The results show that the anaerobic（U1）and upper aeration（U2）reactors are selected to simultaneously cultivate anaerobic granular sludge.The anaerobic granular sludge in the U2 reactor has a better morphology,with a smooth surface and a black color,with a particle size distribution is 1 mm～2 mm,the removal efficiency of COD is more than 97%.Granular sludge in U2 reactor was selected as the main anaerobic granular sludge in the follow-up study.The parameters of U2 granular sludge reactor were optimized.The results show that when the organic load of the influent is 9.98 kg COD/（m³·d）,the C/N ratio is 18～22,and the HRT is 1.5 d,the granular sludge obtained has the best morphology and performance.COD,The removal rates of NH₄⁺-N,TN and TP were 94%,53%,52.%and 52%,respectively.（2）The aerobic granular sludge was cultured in a sequencing batch activated sludge reactor（SBR）,the granular performance and pollutant removal performance during the cultivation process were investigated,and the parameter optimization of the main granular sludge reactor was studied:The results show that the aerobic granular sludge is better in S2reactor when the continuous aeration（S1）and intermittent aeration（S2）are used to cultivate the aerobic granular sludge and the MLSS value reached 5.8 g/L,SVI The value is 46 m L/g,which removes high pollutants.The removal efficiency of COD,NH₄⁺-N,TN,and TP reached more than 90%.Granular sludge in S2 reactor was selected as the main aerobic granular sludge in the follow-up study.The parameters of S2 granular sludge reactor were optimized.When the DO is greater than 6.08 mg/L and the cycle time is 6h,the aerobic granular sludge obtained has the best morphology and performance.The removal efficiency of COD,NH₄⁺-N,TN,TP are 90%,99%,89%,67%,respectively.（3）Under the optimal operating conditions,the performance and operation stability of anaerobic and aerobic granular sludge reactor for the treatment of actual cattle wastewater were studied respectively.The results show that gradually increasing the proportion of wastewater inflow to domesticate the granular sludge has achieved good results.After the domestication is completed,the anaerobic granular sludge is partially decomposed into flocs,the color is black,and the granular sludge is observed by scanning electron microscope.The surface of aerobic granular sludge is uneven and the marginal attached villi.In the scanning electron microscope,the surface of the granular sludge is still dominated by bacilli,and the sludge concentration and sedimentation performance are basically unchanged.The removal rates of COD,NH₄⁺-N,TN and TP reached 94%,90%,90%and 61%,respectively,and the effluent concentrations were 512 mg/L,66.4 mg/L,68.3 mg/L and 7.9 mg/L,respectively.（4）Large-scale sequencing analysis of microbial community structure of sludge samples in each reactor under stable conditions at different stages was carried out to explore the changes of microbial community in different operating stages,and the characteristics of microbial community structure were analyzed at different classification levels.The results showed that Proteobacteria was the main component in the phylum level classification of anaerobic and aerobic granular sludge cultivation,operation optimization and actual livestock and poultry cattle raising wastewater,and there were great differences at the genus level at each stage.In the anaerobic reactor,Acinetobacter was dominant.After treated by livestock and poultry,the dominant Acinetobacter in the sludge decreased to 14.15%.Paracoccus was the dominant species in the aerobic reactor.After the treatment of livestock wastewater,the dominant species represented by Paracoccus decreased from 78.52%to 38.74%.The complex components in the wastewater from livestock and poultry are easy to destroy the living environment of microorganisms in the original anaerobic and aerobic reactor,and the dominant strains of Acinetobacter and Paracoccus have poor adaptability in the treatment of actual livestock wastewater.