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

Dairy effluents contain limited nitrogen for biological treatment. In the present study a cheese whey wastewater was supplemented with ammonia to obtain suitable COD:N ratios. The effects of the organic load and micronutrients on 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 micronutrients were 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, nitrification took place when the organic load was decreased (COD:N = 100:22). The microbial community was analyzed by next-generation sequencing technology. Nitrification was attributed to heterotrophic nitrifiers. Bacteria belonging to Niabella and Diaphorobacter genera and to Planctomycetales order are the main candidates responsible for the nitrification process. Co-treatment of dairy and ammonium-rich wastewater constitutes a promise strategy for the biological treatment of dairy wastewaters.