Effectiveness of pH as Control Parameter for Nitrogen Removal via SND in a Sequencing Batch Reactor

This study investigates the effect of using pH as aeration control parameter on nitrogen removal via simultaneous nitrification and denitrification (SND) in a 10 L acetate-fed SBR. The reactor is operated continuously with quickly terminating the aerobic phase after ammonium depletion, according "ammonia valley" in pH profiles. The results indicate using pH as control parameter on nitrogen removal can save energy and improve nitrogen removal, which allows an increased amount of nitrogen removal via SND from 50% to 86%. After two months of continuous operation with controlled aeration, the setting property of the activated sludge has been significantly improved. The sludge volume index (SVI) has been decreased from 115 ml/g to 57 ml/g. It is also found that larger sludge floes have been formed in the SBR. The average diameter of activated sludge floes is 442 mum, which make it easy to form anoxic microzones within activated sludge floes. Anoxic microzones in the inner of activated sludge floes can reasonably support nitrogen removal via SND.