Electronic Thesis and Dissertation Repository


Doctor of Philosophy


Civil and Environmental Engineering


Shang, Julie Q.


Electroflotation (EF) is a process used to remove suspended particles from water using the gas bubbles generated from the water electrolysis. This dissertation focuses on the fundamental principles and applications of EF in the treatment of industrial wastewaters, and in particular, treatment of automotive paint wastewater. In the first part, an extensive review of applications of electroflotation in the treatment of different categories of industrial wastewaters, including the fundamentals of the process, electrode materials, design aspects and process variables, is conducted. The second part is focusing on the kinetic study, statistical analysis and empirical modeling of available experimental data from batch tests of electroflotation treatment of auto paint wastewater. The kinetics of the TSS (Total Suspended Solids) removal was best described with the second-order rate constants. It was confirmed, statistically, that the initial TSS concentration and Current Density were the most significant process variables. Further, empirical equations of the treatment efficiency were produced. In the third part, an experimental program was carried out in a pilot-scale continuous-flow electroflotation reactor on electroflotation treatment of paint wastewater. The total suspended solids removal was investigated as functions of operational parameters, including the hydraulic retention time (HRT), current density and influent total solids (TS) concentration. The maximum TSS removal rate achieved in the experiments was 95%. It was found that the TSS and turbidity removal rates decrease with the increase of influent TS concentration and are directly related to the applied current density and HRT. The electroflotation system showed to be energy-efficient compared to the commercial systems. In the fourth part of this study, by performing the tracer tests, the hydrodynamics and flow characteristics of the electroflotation reactor were investigated. The experiments were conducted at the various HRTs and under the electric current ON/OFF modes. Because of the presence of stagnant regions in the reactor, the calculated residence times were lower than the theoretical HRTs. It was recommended that by selecting a shorter HRT, better flow characteristics can be achieved. Also, the EF gas bubbles, hydrodynamically, showed to improve the treatment efficiency of the EF reactor.