Study On The Movement Behavior Of Microfauna Of Activated Sludge In Sewage Treatment

Now most of the researchs focuse on microfauna community and species diversity,the movement behavior of microfauna is only described in a simple qualitative way.Quantitative research on the movement behavior of microfauan has not been reported.In this study,video image analysis technology is used to establish a method for the movement analysis of microfauna in activated sludge.Based on the classification of the microfauna movement,the characteristics of instantaneous movement parameters of typical movement types of microfauna by the established method in SBR system was studied.The influence of different influent parameters,microscopic morphological and macroscopic index of activated sludge on the movement speed of microfauna with a free-movement way was analysed also.The main results of this paper are as follows:1)According to the characteristics of microfauna movement behavior in activated sludge,the movement modes of microfauna are classified into two big categories: the free motion and the stretching motion.Free motion can be subdivided into three subclasses: the swimming,crawling and comprehensive motion.Then the swimming motion further be divided into two group: the rectilinear and the curvilinear motion according to the trajectory of movement.The stretching motion is also divided into two sublcasses : the tail-stalk-stretching motion and the worm-body-stretching motion.2)A comprehensive analysis methods is established in this study,which includes the following process in order: a image acquisition,a pre-processing,a target detection and tracking,and calculation of movement parameters.The calculation methods for the movement parameters of microfauna in different modes of motion are as follows: The trajectory,instantaneous speed and average linear speed are choosed to represent the motion characteristics of microfauna with rectilinear motion;The movement parameters including trajectory,adjacent frame motion path and left-right rotation angle,instantaneous speed,average linear speed and average angular speed are choosed to represent the motion characteristics of microfauna with curvilinear and creeping and integrated motion.Microfauna with tail-stalk-stretching motion choose trajectory,instantaneous speed and average linear speed to characterize movement characteristics;The average change rate of morphological area is selected to reflect the movement characteristics of microfauna with worm-body-stretching motion.3)Quantitative characterization of the movement mode of microfauna in activated sludge are as follows: the speed of microfauna with reclinear motion is smaller and stable,such as the average linear speed of P.trichophorum does not exceed 50 ?m/s;the linear speed and angular speed of microfauna with curvilinear motion fluctuate greatly,and are greatly affected by sludge flocs.For example,C.hirtus will change direction of movement immediately when it meets sludge flocs and show acute escape behavior.The average speed of different microfauna in swimming mode is different.The average linear speed of C.hirtus and F.depressa is larger,while that of C.colpoda and L.carinatus is smaller.The trajectory and speed characteristics of E.muscicola in creeping motion are related to sludge flocs.The linear and angular speed of A.lynceus in integrated motion are different in different modes of motion.4)The COD load has different effects on the movement speed of microfauna with different movement mode: the movement speed increases under the condition of influent with high load and decrease under low load.such as the average linear speed and the average angular speed of F.depressa show a trend of reduction;Both high and low load have no effect on microfauna movement speed,for example,the average linear speed of A.acinusare and the average linear speed and average angular speed of A.lynceus are not significantly different.5)The influent pH has different effects on the moving speed of microfauna with different movement mode: the influent with low pH can decrease the movement speed of microfauna,neither does the high pH,such as the average linear speed of A.acinus and the average linear speed and average angular speed of the A.lynceus and Euchlanis sp.decrease in the influent with low pH and does change greatly at high pH.The influent with high or low pH have no effects on the movement speed of microfauna,such as the average linear speed and average angular speed of C.hirtus have no significant difference between the high-pH and the low-pH influent.6)The results show that:(1)There is a certain negative correlation between the movement speed of microfauna and the microscopic indexs of activated sludge flocs.For example,the average linear speed and average angular speed of Euchlanis sp.are negative correlation with the compact size index of the sludge flocs(r=-0.514,p<0.05;r=-0.533,p<0.05).The average linear speed and average angular speed of A.lynceus with crawling movement are negatively correlated with the shape regularity index of sludge flocs(r=-0.563,p<0.01;r=-0.539,p<0.05).(2)There is a certain negativecorrelation between the movement speed of microfauna and the macroscopic indexs of activated sludge.For example,the average linear speed of Euchlanis sp.and F.depressa are negatively correlated with MLSS,and the correlation coefficient are-0.509,-0.567(p<0.05),respectively;the average linear speed and average angular speed of A.lynceus with creeping motion are negatively correlated with SVI(r=-0.607,p<0.05;r=-0.528,p<0.05).