ABSTRACT
Electrochemical methods, as one of the advanced oxidation processes [AOPs], have recently been applied to remove different contaminants from water and wastewater. This study compares the performance of anodic oxidation [AO] and electro-Fenton [EF] methods on waste sludge treatment. This experimental study was performed on real sludge and the effect of operating parameters such as solution pH, operating time, current density, supporting electrolyte and hydrogen peroxide concentration were investigated in a batch reactor. For determination of oxidation and treatability of the sludge, chemical oxygen demand [COD] and total coliform [TC] removal were examined. Pb/PbO[2] and iron electrodes respectively for AO and EF were applied. Experimental data indicated for both AO and EF as the operating time and current density increased, COD removal increased. pH=4.0 and 3.0 and current density=1.75 and 2 A respectively for AO and EF and the concentration = 57.2 mMol of hydrogen peroxide for EF were measured as the optimum amounts of these variables. The removal efficiency of COD in AO and EF process was 76% and 72%, respectively. Of course, the efficiency of EF in TC removal was better and the percentage of TC removal in 60 min for AO and EF was 99.0% and 99.9%, respectively. The amounts of consumed electrical energy for AO and EF were 8.6 and 28.0 kWh kg[-1] COD, respectively. AO was more effective in treatment and mineralization of waste sludge and TC removal than EF in terms of environmental economical features
ABSTRACT
Catalytic ozonation has recently been applied as a new method of contaminant removal from water and wastewater. In this study, copper coated pumice and zeolite were used to catalyze the ozonation of phenol as a target pollutant from aqueous solutions. The pumice and zeolite stone were modified by CuSO4 [1N]. Modified pumice and zeolite were characterized by Adsorption/Desorption Porosimetry [BET] and Scanning Electron Microscope analyses. Ozonation and catalytic ozonation experiments were performed in a 1 L semi-batch reactor containing a prepared phenol solution. The efficiency of catalytic ozonation was investigated by different variables: pH value, contact time, initial phenol concentration, catalyst dose, and radical scavenger. Experimental data indicated that as the pH solution increased, phenol removal increased. pH = 8 was measured as the optimum pH. The removal efficiency in single ozonation process [SOP] was 32% and in the catalytic ozonation process [COP] using modified zeolite and pumice was 51% and 63%, respectively. Moreover, these processes showed a great ability to mineralize phenol [up to 30%]. Using the radical scavenger determined the indirect oxidation as the main pathway of phenol removal in both catalytic processes. The copper modified zeolite and pumice had good performance to remove phenol through catalytic ozonation method.