Research On The Hydrodynamic Behavior On Pollutant Removal In A Reactor With Compound Flow Pattern

In recent years, the studies on baffled reactors are mainly focused on two kinds of reactors, i.e. the anaerobic baffled reactor and baffled biological aerated filter. By integrating the characteristics of the two reactors mentioned above, a sewage reactor with compound pattern of plug flow, baffled flow and mixed flow is specially designed in this thesis and three main operational parameters, including influent flow-rate, mixing speed and the gaps between movable plate and reaction bottom (in briefly noted as GPB) are changed to investigate experimentally their influences on the pollutant removal in the new-designed reactor. These operational parameters are related directly with hydrodynamic conditions in the reactor.The method of artificial inoculation with common activated sludge is used to start up the reactor. At first, the activated sludge obtained from a wastewater treatment plant is acclimated in artificial wastewater to make the sludge meet the needs of removal of nitrogen and phosphate. The acclimated sludge is required to have SV30%of20%to30%, SVI of100to150, pH of6.5to8.0and reaction temperature of20℃. After30days’steadily acclimation, every indictor has reached the expected target, the removal rates of COD, TP and NH4+-N are85%,80%and70%respectively, content of NO3--N is about28mg/L in the first aerobic reaction section.In the reactor with compound flow patterns, keeping the biological conditions constant, three main operation parameters, including the influent flow-rate, mixing speed and GPB are changed respectively to investigate their effect the removal efficiency of COD, NH4+-N and TP from the artificial sewage. The results indicate that the removal efficiency is influenced by all the three factors and that there are optimum compound conditions at which the reactor works most effectively. The optimum conditions are determined as flow-rate of15L/h, mixing speed of400rpm and GPB of50mm.A set of orthogonal tests with three factors and four levels are arranged to examine the relative importance of the three factors, and the results show that the most important factor is flow-rate, next is mixing speed and the last is GBP. In order to discover the comprehensive influence of the three factors on the reactor efficiency, the Peclet number is measured and calculated by use of trace analysis and total64sets of experiments for all the three factors and four levels are done in laboratary. The results indicates that when Pe number is1.38the removal efficiencies of COD, NH4+-N and TP are the highest, and there is a selectable Pe number range of1.04to1.79in practice in which higher removal efficiency is respected. At last,20times of experiments under the optimum hydrodynamic conditions are processed and it is verified that the system is able to be operated steadily and the main pollutants can be removed effectively.