Simultaneous heterotrophic nitrification and aerobic denitrification of wastewater in granular reactor: Microbial composition by next generation sequencing analysis

Abstract

Dairy effluents contain limited nitrogen for biological treatment. In the present study a cheese whey wastewaterwas supplemented with ammonia to obtain suitable COD:N ratios. The effects of the organic load and micronutrientson the biological nitrogen removal process were analyzed in aerobic granular sequential batch reactors(SBRs). Better nitrifying activity (5.04 mg N.(L.h)−1) was achieved at COD:N = 100:12, when micronutrientswere added. In this condition, simultaneous nitrification- denitrification led to a higher inorganic nitrogen removal.Aerobic denitrification was driven by intracellular glycogen. In absence of micronutrients, nitrificationtook place when the organic load was decreased (COD:N = 100:22). The microbial community was analyzed bynext-generation sequencing technology. Nitrification was attributed to heterotrophic nitrifiers. Bacteria belongingto Niabella and Diaphorobacter genera and to Planctomycetales order are the main candidates responsiblefor the nitrification process. Co-treatment of dairy and ammonium-rich wastewater constitutes a promisestrategy for the biological treatment of dairy wastewaters.