SEQUENCING BATCH REACTOR SYSTEM FOR NUTRIENT REMOVAL - ORP AND PH PROFILES

The sequencing batch reactor (SBR) process is known for its flexibilit y to meet a wide range of treatment needs, including nutrient removal. However, information related to the operational stability of SBR nutr ient removal systems and control parameters to adjust the cyclic durat ion is sparse; Consequently, this study was undertaken to identify pro cess parameters (pH and oxidation reduction potential) that could be u seful for monitoring and real-time control purposes. In general, the s ystem achieved removal efficiencies of 91, 98 and 98%, respectively, f or Chemical Oxygen Demand, total nitrogen and phosphate at the solids retention time of 10 days, with a cyclic duration of 6 h. Shock loadin gs of nitrogen (20 mg dm(-3) of NH4+-N, four cycles) exhibited little impact on effluent quality, except for a higher nitrate content. Activ ated sludge settled well throughout the entire study period. Several s ignificant points associated with different reactions within SBR cycle , e.g. end of nitrification, end of phosphate release and completion o f phosphate uptake, were identified in pH profiles. Slope changes in p H profiles (dpH/dt, or d(2)pH/dt(2)) were found to better represent th e corresponding biological reactions. The application of these signifi cant points in pH profiles as real time control parameters appears pro mising.