Abstract
Simultaneous removal of selenite (SeIV), tellurite (TeIV) and nutrients by aerobic granular sludge (AGS) was investigated. A sequencing batch reactor (SBR) was operated with increasing SeIV and TeIV (up to 500 µM each) for 205 days to evaluate metalloid oxyanion and nutrient removal. AGS efficiently removed SeIV and TeIV by readily converting them to biomass associated forms. The total Se and Te removal efficiencies were higher at 98% and 99%, respectively. Formation of biomass-associated Se0 and Te0 was confirmed by XRD, Raman spectroscopy and SEM-EDX. Feeding of SeIV and TeIV elicited inhibitory action on ammonium removal initially, nonetheless removal performance was recovered during the subsequent cycles. Ammonium, total nitrogen and phosphorus removals were stabilized at 85%, 80% and 75%, respectively, at 500 µM of SeIV and TeIV. Sequencing of 16S rRNA gene confirmed enrichment of known SeIV and TeIV reducing bacteria in the granules. qPCR and removal kinetics supported ammonia removal via nitritation-denitritation. This work demonstrates functional capabilities of AGS for effectively removing toxic SeIV and TeIV oxyanions apart from performing simultaneous COD, nitrogen and phosphorus removal. Efficient biological nutrient removal in the presence of toxic SeIV and TeIV concentrations, suggests robustness of AGS and its resilience to toxic contaminants.
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