An integrated mainstream and sidestream strategy for overcoming nitrite oxidizing bacteria adaptation in a continuous plug-flow nutrient removal process

Abstract

An integrated mainstream aeration and sidestream sludge treatment was demonstrated to be effective in overcoming the adaptationof nitrite oxidizing bacteria (NOB) in an anoxic/oxic process. Results showed that by employing the alternating free nitrous acid and free ammonia (FNA/FA) sidestream sludge treatment alone, nitritation was established but varied, which was addressed by integrating alternating aeration with step feeding (ALASF) in reactor. Two critical considerations contributed to stable effluent nitrite accumulation (>83.8 %)and nitrogen removal (>83.0 %): 1) aerobic sludge rather than return sludge should be taken for FNA/FA treatment to avoid anoxic starvation which facilitated NOB recovery; 2) ALASF ensured timely denitritation and created constant anoxic disturbance for NOB inhibition. Nitrospira and Nitrobacter after 540-day operation were 0.38 % of seed sludge.A20 % reduction of operating cost was obtained in this nitritation process. This study moved nitritation one step closer to application in continuous plug-flow process from municipal wastewater.

Keywords: Anoxic-oxic process; Free nitrous acid and Free ammonia (FNA/FA); Nitritation; Nitrite oxidizing bacteria; Step feeding.