The Effect of Short-Term Shock Load on the Performance of SAFs with Different Media

This study was carried out to apply short-term shock load to investigate and compare microbial responses and interactions of submerged aerated filters (SAFs) with wool and Kaldnes. It was presented that the results from a transient hydraulic shock of reducing the hydraulic retention time (HRT) by half to a HRT of 1.0 hours for 2.0 hours and followed by a return to the steady state. At the beginning of shock load, the effluent concentration of TOC, SS, Turbidity and ammonia increased rapidly. SAFs quickly returned to normal operation 6.0-8.0 hours after the hydraulic shock and were then stable. The wool reactor had slightly more resistance than the Kaldnes, which indicated wool had better filter ability, biomass kinetics and hydrodynamic turbulent mass transfer avoiding nutrient limitation. The rapid recovery suggested the reactor had less sensitive to certain disturbances since some mixing and dilution of incoming wastewater may take place inside SAFs and the biofilm of SAFs protects the embedded bacteria from potentially harmful environmental conditions.