The Growth And Reproduction Of Vorticella In Activated Sludge And Its Influence On The Sludge Purification System

Vorticella are sessile ciliates,which are the most common indicator microorganisms in sewage treatment.The current research mainly focuses on the indication function of the vorticella as the dominant species,but there is little research on the growth and reproduction process of the vorticella in the activated sludge and its influence on the activated sludge purification system.In this study,firstly,on the basis of studying the growth process of activated sludge culture and domestication of vorticella,the growth curve of vorticella was drawn,and the reproduction process of vorticella and their special forms were studied through the microscope online continuous follow-up observation,and then the main environment was explored.The influence of factors（COD concentration,sludge concentration,aeration intensity,temperature）on the growth of the vorticella,as well as the characteristics of the sludge and the removal of pollutants at different stages growth of the vorticella.Finally explore different environments（COD concentration,impact load,sludge concentration,sterilization active sludge,aeration strength）the main study is as follows:（1）In the process of activated sludge culture and domestication,the growth of the vorticella species conforms to the logistic growth curve,and the growth regression equation is N_t=26180.961/(1+e^{13.486-0.385t})（R²≥0.93）.The growth process can be divided into four stages:early growth period（11-26d）,growth acceleration period（27-33 d）,growth deceleration period（34-49 d）and growth stabilization period（50-64 d）.（2）There are two ways of reproductive methods:asexual reproduction and sexual reproduction.There are 4 different forms during the second asexual reproduction.Sexual reproduction is combined reproduction.The contents of the gametes are gradually divided into the main body,and the gametes gradually become smaller and then disappear;vorticella becomes a swimmer in two ways:one is the shape of the vorticella body does not change significantly when it is detached from the tail stalk.Second,another vorticella became thinner and longer when detached from the tail stalk,and finally became a cylinder.The vorticella will have the phenomenon of"head bubbles"when hypoxia.When the hypoxic environment cannot be improved in time,the vorticella will die or become a cystic state,and the vorticella will"out of the package"when the environment improves.A new form of helminth was discovered—a stalked swimmer.The vorticella,together with the caudal peduncle,fell off the fixed substrate and looked for activated sludge flocs with many bacterial food sources.The cilia around the mouth were constantly shaking for food.（3）When the influent COD concentration is 600mg·L^-1,it is more suitable for the growth of the vorticella.The influent COD concentration is 200,400,1200mg·L^-1 and the vorticella density is smaller during the whole experiment.The influent COD concentration is 800 mg·L^-1 and 1000 mg·L^-1 vorticella density fluctuates greatly;the sludge concentration of 2000-4000mg·L^-1 vorticella grows better,and the higher the sludge concentration,the greater the peak density of vorticella.When the sludge concentration is 1000,5000,6000 mg·L^-1,it is not conducive to the growth of the vorticella;when the aeration intensity is 0.1L·min^-1 and 0.2L·min^-1,it is suitable for the growth of the vorticella,and the aeration intensity is 0.3-0.6L·min^-1 is unfavorable to the growth of vorticella,the more suitable dissolved oxygen concentration range for the growth of vorticella is between 5.07-6.56mg·L^-1;the higher the temperature at 5℃-30℃,the faster growth rate of vorticella.The earlier the peak appears,the 15°C and 20°C vorticella can maintain a stable growth density for a long time,which is more suitable for the growth of vorticella.（4）The COD removal rate is relatively stable at different stages of the vorticella’s growth.The maximum COD removal rate is 83.43%during the initial growth period of the vorticella.The ammonia nitrogen removal rate decreases continuously at different stages of the vorticella’s growth,and the removal rate is between 58%and 95.44%.During the period,the removal rate of TP showed a trend of first decreasing and then increasing.The removal rate fluctuated greatly.The maximum removal rate was 92.31%during the initial growth period of the vorticella.The correlation results showed that the change of vorticella population density and COD removal rate,SVI value has no correlation,and is negatively correlated with NH₄⁺-N removal rate（r=-0.726,p=0.01）,TP removal rate（r=-0.527,p=0.01）,and MLSS（r=-0.734,p=0.01）.There is a significant positive correlation with the area of sludge flocs（r=0.890,p=0.01）.（5）The growth of vorticella under different influent COD concentrations has little effect on the removal rate of COD.The growth of vorticella at low concentrations（C200-C600）is not conducive to the removal of ammonia nitrogen,and the growth of vorticella at high concentrations（C800-C1200）is not conducive to the removal of ammonia nitrogen.Growth is conducive to the removal of ammonia nitrogen,and the removal rate of ammonia nitrogen has a tendency to increase;under shock load,the sludge concentration increases rapidly,exceeding the sludge reduction capacity of the vorticella;the difference in COD removal rate under different sludge concentrations is not very large.The removal rate can basically reach more than 80%.When the sludge concentration is1000-3000mg·L^-1,compared with the sludge concentration 4000-6000mg·L^-1,it is more conducive to the removal of ammonia nitrogen when the vorticella grows;sterilizing activated sewage In the sludge system,after inoculation of the vorticella,the growth of the vorticella in the sterilized activated sludge has a certain contribution to the removal of COD,which can significantly improve the removal effect of ammonia nitrogen;the aeration intensity is 0.1L·min^-1 and 0.2L·min^-1 vorticella has a growth trend which is beneficial to the removal of ammonia nitrogen,and the aeration intensity of0.3-0.6L·min^-1,vorticella has no growth trend,and the ammonia nitrogen removal rate is low.