Seasonal degradation of textile effluents through the solar photo-Fenton process mediated by ferrioxalate: discoloration and behavior of solids

ABSTRACT This work evaluates the solar photo-Fenton process mediated by ferrioxalate as a primary treatment of raw textile effluent (E1) and as a polishing step, after active sludge process (E2). For a year, at least once a month, the color removal’s efficiency and solids’ behavior in the oxidative process treatment were analyze under natural conditions of light, temperature and effluents characteristics. The operational parameters values were: 50 mg L-1 iron, pH 5, 525 mg L-1 H2O2, introduced in decreasing doses. The oxalate was added at the molar ratio of 1:3 [Fe+3:(C2O4)-2]. The color removal of E1 was 60% for 690 W m-2 of radiation intensity and 95% for 620 W m-2 intensity to E2. Considerable increases were observed in turbidity and suspended solids due to the iron precipitation and the consequent coagulant action. In sunny days, the complex degradation in E2 resulted in high settle ability of solids in the final effluent, resulting in a clear supernatant. This has not happened in cloudy days.