Study Of The Structure Characteristics Of The Flocs Of Heterogenic Bulking Activated Sludge

In order to explore the accurate effects of the structure characteristics of bulking activated sludge flocs on the settleability of sludge.The heterogenic bulking sludges under different influent conditions were domesticated,and the sludge floc parameters were classified into several groups to analyze the basic characteristics of the bulking activated sludge.Based on principal component analysis?PCA?method,the index system of floc structure characteristics was established to research the change law of the floc structure characteristics of heterogenic bulking sludge.Partial least squares?PLS?regression was used to explore effects of floc structure characteristics on the sludge's settleability SVI.The functions of SVI based on floc structure characteristic parameters were obtained.The main research results are as follows:1)Heterogenic bulking sludge occurred in four SBR systems with different influent conditions:due to shortage of either P or N source,SBR1,SBR2 and SBR3 systems all ended up with filamentous bulking,and the less contents N and P were,the more severe filamentous sludge bulking became.While viscous bulking happened to SBR4 system?shortage of element P?.There was a positive correlation between SVI and COD removal rate in the filamentous bulking sludge system.On the contrary,SVI showed a negative correlation with COD removal rate in the viscous bulking sludge system.Except for the SBR1 system,regardless of viscous or filamentous bulking sludge,the polysaccharide content of EPS in bulking sludge was higher than that of the normal sludge,while the protein content of EPS in bulking sludge was lower than that of the normal sludge.The change of EPS composition affected sludge settleability,and the effect of polysaccharide was greater?except for SBR2 system?.EPS in tight inner layer?layer T?was the key impacting indicator to direct SVI in the filamentous bulking.On the contrary,EPS in incompact outer layer?layer S?was the key impacting indicator to direct SVI in the viscous bulking,which were the main cause of sludge bulking.2)The floc structure characteristic of filamentous bulking activated sludge had been defined as 5 classes,which were named as floc size?SZ?characteristic,floc stretch?ST?characteristic,floc compactness?CO?characteristic,floc regularity?RO?characteristic and floc filamentous?FL?characteristic,respectively.The structure characteristic index of filamentous bulking sludge system established by PCA method are as follows:SZ=3.63ZP_cond+3.29ZP+2.74ZL+2.44ZW+2.41ZF_max+2.37ZD_eq+2.35ZA_meanST=3.10ZExt+1.99ZA_sp+1.82ZBR+1.71ZARCO=18.48ZH+2.92ZHR+0.34CompRO=2.35ZPR+1.944ZRo-0.895ZFF-0.867ZFDFL=1.41ZFLA+1.41ZFLSSThese index functions above showed that the seven parameters all contributed to the SZ on which the ZP_cond parameter had the greatest impact;the parameter ZExt had the greatest impact on the ST;the parameter ZHs played a decisive role in the CO;the parameter ZPR had the greatest impact on the RO;the parameter ZFLA and ZFLSS had the same impact on the FL.3)The floc structure characteristic of viscous bulking activated sludge had been divided into 4 classes,which were named as floc size?SZ?characteristic,floc stretch?ST?characteristic,floc compactness?CO?characteristic and floc regularity?RO?characteristic,respectively.The sludge structure characteristic index of viscous bulking system setted up by PCA method are as follows:SZ=2.98ZP_cond+2.80ZF_max+2.75ZP+2.66ZL+2.51ZW+2.49ZA_mean+2.46ZD_eqST=2.20ZA_sp+1.43ZAR+0.28ZBR-1.84ZExtCO=1.76ZComp-1.73ZH+1.71ZHRRO=2.06ZRo-2.03ZPR-2.04ZFF+1.89ZFDThese index functions above showed that the seven parameters all contribute to the SZ on which the ZP_cond parameter had the greatest impact;the parameter ZA_sp had the greatest impact on the ST;the parameter ZComp played a decisive role in the CO;the parameter ZRo had the greatest impact on the RO.4)There was a strong correlation between the SVI value and the structure characteristics indexes of floc in the filamentous bulking system,and it showed the FL index produce the greatest impact on the settleability of filamentous bulking sludge.Regression model function of SVI was as follows:SVI=|0.610FL-0.351SZ-0.33ST+0.178RO-0.005CO|?R²=0.779?There was a pretty correlation between the SVI value and the structure characteristics indexes of floc in the viscous bulking system,and SZ had the greatest impact on the settleability of sludge.Regression model function of SVI was as follows:SVI=|-0.554SZ+0.409ST+0.272RO-0.171CO|?R²=0.688?5)The observation value of SVI in the filamentous bulking sludge showed a pretty linear correlation with the predicted value,and the R² was 0.801.The SVI observations of the viscous bulking sludge were linearly correlated with the predicted values,with a R² of 0.664.The floc index of microscopic structure characteristics could accurately reflect the settleability of activated sludge,the SVI regression model function based on filamentous bulking floc structure characteristics tended to match the actual situation.