Abstract
Organic shock loads often hinder biological wastewater treatment systems from meeting discharge standards, as a result, these systems frequently fail to achieve the required level of treatment so, the potential impact of these loads was investigated using laboratory-scale sequencing batch reactors (SBRs). Short-term (4.5 h) exposure to 721.25 - 1515.36 mg COD/L shock loads reduced the removal ratios of COD by 3.48 % – 31.73 % compared with the control. A mathematical model was developed for COD decomposition and the results obtained from the model were approximately close to the experimental data, and the maximum difference between the experimental and the theoretical removal rates was 3.36 % at a shock organic load of 1019.20 mg COD/L. In addition, the reactor performance was evaluated under successive organic shock loads so, a constant influent COD value of 1249.5 mg/L was applied for eight successive batch cycles and the results indicated that the removal ratio gradually improved with successive loading. As well, to enhance treatment efficiency under organic shock loads the performance of the reactor was evaluated for different MLSS concentrations of 2000, 2600, 3200, 3900, 4200, 4600, 4825, and 5250 mg/L. Three different organic shock loads with COD concentrations of 1043.04, 1205.36, and 1560 mg/L. COD removal ratios of 96.23 %, 86.18 %, and 75.81 % were achieved for the first, second, and third shock loads respectively at a MLSS concentration of 4825 mg/L however, it dropped when MLSS concentration increased to 5250 mg/L.