The removal of formaldehyde from concentrated synthetic wastewater using O3/MgO/H2O2 process integrated with the biological treatment

Abstract

The catalytic advanced oxidation process (CAOP) of O(3)/MgO/H(2)O(2) was integrated with a sequencing batch reactor (SBR) system to completely treat concentrated formaldehyde wastewater, demonstrating that this combination is an effective method for treating such wastewaters. The influence of several operational variables--including pH, MgO powder dosage, and the concentrations of H(2)O(2) and O(3)--was investigated for the O(3)/MgO/H(2)O(2) degradation of a 7000 mg/L formaldehyde wastewater. The optimum conditions were found to be a pH of 8, 5 g/L dose of MgO powder, 0.09 mole/L concentration of H(2)O(2), and 0.153 g/L min dose of O(3). The formaldehyde and COD concentrations were reduced 79% and 65.6%, respectively, in the CAOP for 120 min of reaction time under the optimum condition stated above. The remaining concentrations of formaldehyde and COD were 1500 mg/L and 3200 mg/L, respectively, in the effluent. The degradation of formaldehyde in CAOP was determined to be a first-order reaction with a constant of 0.015/min, and radical oxidation was the predominant degradation mechanism. This effluent was post-treated in SBR system for a total cycle time of 24h. The SBR completely removed the formaldehyde and removed 98% of the COD, reducing the COD concentration to lower than 60 mg/L. Therefore, the integrated O(3)/MgO/H(2)O(2) and SBR process is demonstrated as a promising technology for the complete treatment of wastewater with high concentrations of toxic and inhibitory compounds such as formaldehyde.