| Aerobic granular sludge has become a widely used technology in water treatment technology due to its good sedimentation performance,ability to accumulate high concentration of microorganisms,easy control conditions,strong impact resistance and high toxicity.The main cultivation methods include adding carriers,inoculating mature granular sludge and continuing to cultivate.The factors that affect the formation of aerobic granular sludge are complex and diverse,such as influent water quality,organic load,hydraulic retention time,hydraulic shear force,dissolved oxygen and reaction.There are many factors such as the type of vessel,the current research difficulty of aerobic granular sludge is that the granular structure is prone to instability.After cultured for a period of time,the size of the sludge increases and the filamentous bacteria increase,resulting in sludge swelling.An EC-SBR reactor with asymmetric periodic commutation and low-voltage electrocoagulation to promote aerobic granular sludge culture was developed in this study.The experimental simulated wastewater was used in experiments(sodium acetate and ammonium sulfate as carbon and nitrogen sources).Water quality.Activated sludge from the aeration tank of the southern Shenyang sewage treatment plant was used as inoculated sludge to cultivate aerobic granular sludge.The synergistic effect of aerobic sludge granulation with iron ions and a low voltage electric field was investigated,and 40L Sludge granulation effect of electrocoagulation under different aeration flow rates per hour and 100L/h.The test is performed on aerobic particles by measuring sludge physical properties(MLSS,SVI,sludge particle size),sludge removal efficiency(COD and inorganic nitrogen removal rate),and sludge microbial community structure(high-throughput sequencing analysis).The physical and chemical properties of the sludge were evaluated and the metal ion hypothesis and EPS hypothesis were verified.The experimental research content and conclusions are as follows:(1)It was confirmed that both iron ions and electric field promote synergistic effect on sludge granulation.The sludge granulation with C-Fe electrode plate was the best,with an average particle size of 1.2mm.The particle size was 33.33%larger than that of the blank control group.Low-voltage electrocoagulation can promote the formation of aerobic granular sludge with a tighter and denser micelle structure.And verified the metal ion hypothesis of aerobic granular sludge.(2)Electrocoagulation can promote the combination of iron ions and sludge.The content of aggregate iron ions in the sludge with pure iron ions added was 28.4 mg/gMLSS,which was lower than the aggregate iron ions 37.6 mg/g MLSS under electrocoagulation.(3)Granulation of sludge promotes the secretion of EPS and increases the PN/PS ratio in EPS.The PN/PS of the original sludge is 1.27,and after 60 days of culture,it is 2.82,2.54,3.11,and 2.98,respectively.Increasing the ratio of the hydrophobic region of the PN to the hydrophilic region of the PS helps to reduce the number of water molecules bound by the bacteria,thereby helping the formation of bacterial micelles and sludge granulation culture.The larger the sludge particle size,the higher the EPS content.The EPS hypothesis is verified.(4)The aerobic granular sludge cultured under low voltage electrocoagulation has higher nitrogen removal efficiency.The larger the particle size of the sludge,the simultaneous nitrification and denitrification can be performed.Under the condition of oxygen limitation(DO=2.6-2.7mg/L),the TN removal rate of sludge under electrocoagulation can reach 78%and 66%.,Higher than the control group.With the formation of sludge granulation,the abundance and diversity of microorganisms in sludge have decreased.The sludge microbial diversity at aeration flow rate of 100L/h was more than 40L/h,and the microbial abundance and diversity under electrocoagulation were lower than those of the blank control group.Electric fields and iron ions can inhibit the growth of some microorganisms.The dominant flora of granular sludge is mostly distributed in Proteobacteria and Bacteroidetes.Low voltage electrocoagulation can increase the abundance of Zoogloea fungus micelles and inhibit the growth of filamentous bacteria such as Thiothrix,thereby making the granular sludge structure denser. |
