Influence Of Poly Aluminium Chloride Dosing Time On Formation And Extracellular Polymeric Substances Of Aerobic Granular Sludge

This article analyzed the formation process of the aerobic granular sludge and the differences of particle properties, and researched the content changes of extracellular polymeric substances and the relationships of SVI and MLSS with the EPS, and studied the impacts of the PAC dosing time on the spatial distribution of the EPS in the particles under the conditions of different poly aluminium chloride dosing time, by dosing PAC to the reactors in 1-7 days and 8-14 days respectively during the process of cultivating aerobic granular sludge.The main findings of this study are as follows:(1) In the first 1-7 days of the SBR reactor without adding the coagulant, the number of microorganisms in the reactor barely changes, signifies that the microorganisms are in the lag phase; In the 8-14 days, the number of microorganisms in the reactor increases rapidly, signifies that the microorganisms are in the logarithmic phase.(2) Under the conditions of dosing PAC to the reactors in 1-7 days and 8-14 days respectively during the process of reactors, the time of sludge granulation in reactor R1 and R2 is on the 30 th day and the 24 th day, respectively; The granules formation time of the reactor adding PAC in 8-14 days is 6 days ahead of time,and the sludge granules has regular shape, uniform size, compact structure, high mechanical strength, good contaminants removal performance, excellent settling performance, powerful anti-shock loading capability, and its microbial morphology is more plentiful.(3) The result of the EPS contents in the aerobic granular sludge under the enhancing granulation conditions shows that: the total EPS and proteins content is higher overall and increases quickly with the formation of granules and then decreasedslightly, and stayed stable after the granules matured. while the polysaccharide content increases slightly, then stayed stable, as a whole, the content of polysaccharide rarely changes; The value of proteins/polysaccharides during the process of granules formation increased by more than 2.5 times,and total EPS and proteins content and the value of proteins/polysaccharides in the sludge of the reactor adding PAC in 8-14 days are higher,which are conducive to the formation and the stability of granular sludge.(4) In the reactors, the amount of total EPS and protein content and the value of proteins/polysaccharides are negatively correlated with the SVI of the reactors, and the correlation coefficients were R=-0.76519 and R=-0.73531 and R=-0.76468, respectively,however, polysaccharides content has no significant linear relationship with the SVI of the reactors, and the total EPS content has no significant correlation with the MLSS of the reactors.(5) The PAC dosing time has a great influence on the spatial distribution of the EPS and living cells in aerobic granular sludge, which has little effect on the protein andα-polysaccharides, and the distribution of the protein and α-polysaccharides is more evenly, while, the distribution of the β-polysaccharides and lipids and living cells are more different under the different operating conditions: in the aerobic granular sludge of reactor adding PAC in 1-7 days, the β-polysaccharides is distribution on the outside of particles, the lipids is most concentrated in the grain interior, and the distribution of living cells is in the interior of the particles; in the aerobic granular sludge of reactor adding PAC in 8-14 days, the β-polysaccharides is concentrated in the core of the particles, the living cells and most of the lipids is distribution in lateral region.