Ibrahim Muhammad Al-Harazin2022-05-182022-05-184800https://drepo.sdl.edu.sa/handle/20.500.14154/2653The effect of the organic loading rates and the solids residence time (SRT) on the aerobic treatment of phenol and o-cresol bearing wastewater by sequencing batch reactors (SBRs) was investigated. SBRs were utilized to treat phenol and o-cresol, aerobically at a hydraulic retention time (HRT) of one day and varying SRTs. The reactors achieved over 99.5% removal of phenol and o-crsol at toxicant loading in the ranges of 100-800 kg phenol/m³-day at SRTs of 10 days and above with the effluent BOD and TSS concentrations consistently about 5 and 12 mg/1, respectively. However, a rapid breakthrough resulting in only 65% removal efficiency of phenolics at loads of 800 kg phenol/m³-day occurred at 3 and 5-day for phenol, and o-cresol, respectively, simultaneously with a breakthrough of total suspended solids (TSS). The rapid deterioration in effluent quality ensued toxicant loadings of 0.7 mg phenol/mg MLVSS and 0.8 mg cresol/mg MLVSS. Better than 94% phenol removal efficiency was achievable at the 5-day SRT biotreatment.enThesis