| Aerobic granular sludge?AGS?is an agglomerate with larger particle size formed by microbial cells through a series of physical,chemical and biological effects.Compared with common activated sludge,AGS has sedimentation,good performance,high biomass concentration and strong impact load characteristics.However,the mechanism is not yet clear,and it takes several weeks or even months to form from conventional activated sludge.This is one of the bottlenecks that hinder the widespread use of aerobic particles.Iron is a basic element which is necessary for microbial life activities.It plays an important role in the electron transfer of biological oxidation,and the extracellular polymer?EPS?produced by bacteria can also interact with iron.Therefore,in this paper,based on the theory of using crystal nucleus culture AGS,the research on the culture and performance of aerobic granular sludge with Fe?OH?3 flocs as granular nuclei were studied.The test uses a SBAR?Sequencing Batch Airlift Reactor?for automatic water inlet and outlet operations.The required influent water for the cultivation was sucrose,NH4 Cl,KH2PO4 and other nutritious substances as the simulated domestic sewage of carbon source,nitrogen source and phosphorus source.Research indicates:?1?In the SBAR reactor,Fe?OH?3 floes with a sludge mass ratio of 3%?R2?,5%?R3?,and 7%?R4?were added as aerobic granular sludge.The grain nucleus was compared with the blank control group?R1?that did not undergo treatment.The granulation time of the control system,the 3% group,the 5% group,the 7% group,and the four groups of reactor systems was 35 d.31d,27 d,27d.It can be seen that the addition of Fe?OH?3 floc as an aerobic granular sludge granulation nucleus can shorten the cultivation time of aerobic granular sludge,thereby improving the engineering efficiency to some extent.?2?In the process of sludge granulation,the sludge concentration?MLSS?,sludge settling performance?SVI?,sludge particle size,and sludge microbial activity were monitored periodically to characterize AGS.Growth conditions and performance.The sludge concentrations of the four reactor groups were all stabilized at 8.7 mg/L or more.The R3 sludge with the Fe?OH?3 content of 5% had the highest concentration of 9.2 mg/L and the control group had the lowest R1 of 8.75 mg/L.At the same time,R3 granular sludge is also superior to the other three groups in sedimentation performance,its SVI value is 19.5m L/g,while R1,R2,R4 are 22.2m L/g,20.1m L/g,22.6m L/g;After the granular sludge matured,the sludge particle size reached 0.6mm,in which R3 and R4 were slightly larger than R1 and R2.Regular monitoring of sludge dehydrogenase activity?TTC?revealed that during the granulation of sludge,the activity of dehydrogenase increased rapidly.After the granular sludge matured,no significant changes occurred.At the same time,low content?less than 5%?of was found.Fe?OH?3 has a promoting effect on TTC,and when it is higher than 5%,it shows an inhibitory activity.?3?Through the daily microscopic examination of the granular sludge,it can be seen that the roundness and integrity of the granular sludge?R2,R3,R4?cultured with Fe?OH?3 flocculation is higher than that of the control group R1.The mature aerobic granular sludge in the reactor was randomly selected and cut from the middle,and the internal structure was observed using a microscope at a magnification of 40 times.It was found that there was dark red Fe in the granular sludge fed with Fe?OH?3 floes..There is no special color level inside the control group.?4?In order to better cultivate the AGS with good mutual processing performance,the influent C: N: P was maintained at 100:10:1 in the conventional culture stage.Before the success of granulation of sludge,the influent COD concentration was maintained at about 660 mg/L,and the influent COD concentration was maintained at 880 mg/L after successful granulation.The final COD and TN removal rates were around 95% and 78%,respectively.The effluent ammonia nitrogen is almost zero.?5?By conducting comparative tests under the same kind of conditions,it is concluded that when the Fe?OH?3 floe content in the reactor is 5%,the effect of the sludge granulation and the granular sludge properties is best.The control group and 5% groups in the test group were set as control group in the test group.The remaining two groups were removed and the denitrification performance of aerobic granular sludge was studied.The TN removal rate of control group was 80.4%,which was higher than that of control group 76.5%.After changing the system aeration,nitrogen content and p H value,it was found that high aeration intensity has an inhibitory effect on denitrification;when the nitrogen concentration in the influent water is too high,the relative removal of nitrogen increases and the removal rate decreases;aerobic particulate pollution When the mud is run under acidic conditions,the denitrification performance is significantly reduced.It can be concluded that Fe?OH?3 floc dosing can resist the external unfavorable factors to a certain extent.?6?The composition analysis of granular sludge by XRF technology showed that the main elements in granular sludge were C and O elements.Among them,the ratio of Fe to Fe was 2.351% in test group with Fe?OH?3 floc,which was higher than the control.0.129% of group control group and 0.1259% of common activated sludge.In the control group,the Ca and C elements were higher in control group,which were 3.131% and 34.2%,respectively.It shows that if an artificial agent is added with inert substances,the sludge system will use this material as its own granulation nucleus.If no artificially added material is used,the sludge system will deposit some inert substances?such as Ca CO3?as sludge granulation crystals.nuclear.?7?The 3D-EEM technology was used to analyze the EPS components of the sludge during granulation and sludge maturation.The fluorescence intensity of the characteristic peak A representing the protein and the characteristic peak B representing the humic substance in the sludge granulation phase was higher than that of the sludge.During the maturation stage,the sludge granulation period was demonstrated and the sludge was secreted by EPS for sludge granulation.At the same time,the fluorescence peak A representing protein substances in control group of the experimental group containing Fe?OH?3 and representing humic acid substances was found.The intensity of the characteristic peak B was stronger than that of control group,indicating that the Fe?OH?3 dosing helped the granular sludge to secrete more protein and humic acid.?8?The composition of EPS extracellular polymer?EPS?was analyzed by Fourier transform infrared spectroscopy?FTIR?.It was found that the components of EPS in AGS were mainly composed of aspartic acid and other proteinaceous substances,in the sludge granules.During the period of high concentration,when the granular sludge matures,the concentration decreases.This shows that these substances play an important role in the granulation of sludge,and also prove that the protein in EPS is the main influencing factor of sludge granulation. |
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