Spatial Distribution Of Elements And Changes Of Microbial Community Structure During The Strengthening Granulation Process Of Aerobic Sludge

Aerobic granular sludge has attracted wide attention from researchers because of its perfect settling performance,dense structure,high biomass and adsorption of harmful substances.However,long start-up time and low granule stability are the main challenging issues for its application.During the initial stage of aerobic granulation(10~16 d),the aluminum sulfate feeding strategy was applied to accelerate the formation of aerobic granules and the aluminum sulfate feeding strategy was also applied to enhance the reformation of aerobic granules.The elements content were analyzed by X-ray fluorescence spectrometer(XRF).Scanning electron microscope combined with energy dispersive X-ray detector(SEM–EDX)were used to analyzed the spatial distribution of elements.DGGE were used to analyze the characteristic of microbial community structure.The results showed that:(1)During the initial stage of SBR(10~16 d)reactor operation.The addition of aluminum sulfate can accelerate the granulation process of aerobic sludge.The granules cultivated with aluminum sulfate had more compact structure,more biomass,larger size and better settleability.Meanwhile,the aluminum sulfate feeding strategy did not affect the removal efficiency of COD and NH4+,obviously.To some extent,the aluminum sulfate feeding strategy can enhanced the removal efficiency of TP.(2)After chemical dosing,the content of aluminum in granules linearly decreased from 45.69 ± 0.55 %(16 d)to 1.09 ± 0.39 %(43 d).Meanwhile,the content of P and S recovered from 7.21 ± 0.047 % and 32.11 ± 0.23 % to 13.64 ± 0.071 % and 47.82 ± 0.21 %,respectively.Aluminum and phosphorus mainly accumulated in the core of the mature granules and was in the form of precipitate.During the chemical dosing,the accumulating way of microorganism depend on the physical flocculation of flocculant,mainly.After chemical dosing,the self-flocculating of microorganism gradually replaced the inorganic flocculation of flocculant,became the main method of microbial accumulation.The result may infer that Al3+ enhanced formation is a coupling process between physicochemical-biochemical effects.(3)DGGE profile and the sequencing results showed that there was no obvious difference of the microbial community between the two reactors.It meant that the addition of aluminum sulphate made no difference between the two reactors.In the process of enhanced formulation,Proteobacteria were the dominating bacterium in the granules and Pseudomonas was the majority in Proteobacteria.(4)A short-term aluminum sulfate feeding strategy was applied to accelerate the re-formation of disintegrated aerobic granular sludge.The granules cultivated with aluminum sulfate had a better characteristics of sludge and higher amount of bacteria.At the same time,the addition of aluminum sulfate makes a certain changes in the microbial EPS components of the sludge.DGGE profile and the sequencing results showed that the chemical dosing granules had an abundant diversity of the microbial community at 7 days after aluminum sulfate dosing.In the 27 days after chemical dosing,there was no obvious difference of the microbial community between the two reactors.It may infer that the disintegration of aerobic granular sludge may lead to a decrease in the diversity of its internal microbes and the addition of aluminum sulfate accelerates the recovery of microbial population diversity,effectively.