Effect of hydraulic retention time and dissolved oxygen concentration on the biodegradation efficiency of phenol in an activated sludge reactor at different organic loading rates

Phenol is an important contaminant in wastewater from processing and refining plants, its presence in ecosystems is related to the production and degradation of numerous pesticides. Their toxic action is related to their hydrophobicity, generation of organic radicals and reactive oxygen species, causing mutagenesis and carcinogenesis in humans and other living organisms. In this research, an activated sludge system was studied for the treatment of wastewater with high concentration of phenol for reuse, varying the hydraulic retention time and dissolved oxygen concentration. The results showed the best COD removal rate (55%) and phenol biodegradation (49%) during experiment IV, at a wastewater dilution rate of 25% (v/v), dissolved oxygen (DO) feed of 1.5 ppm, hydraulic retention time (HRT) of 2.81 days and organic load (Bv=7.5kgCOD/m3.d).