Simultaneous removal of nitrate and phosphate from wastewater by siderite based autotrophic denitrification

The potential of simultaneous removal of nitrate and phosphate from wastewater by a single anaerobic Fe(II) oxidizing denitrifiers (the strain PXL1) was assessed using siderite biofilters under different influent TOC concentrations and hydraulic retention times (HRTs) over a 160-day trial. Higher TOC concentrations promoted NO3− removal, while there was no significant influence on PO43− removal. Lowering down HRT from 10 h to 5 h did not significantly influence NO3− and PO43− removal. The NO3− removal performance and microbial community structure in the biofilters indicated that NO3− was reduced to N2 by both strain PXL1 and heterotrophic Acidovorax delafieldii. Iron content analysis of the used siderite along the biofilters showed that PO43− removal was improved by the bio-oxidation of Fe(II) in siderite to Fe(III) via the strain PXL1. The coexistence of the strain PXL1 and natural siderite in nitrate-contaminated aquifers provides a practical technology for in situ remediation of nutrient contaminated waterbodies. [Display omitted] •Simultaneous nutrient removal from wastewater with low organic matter was achieved.•Siderite is an efficient electron donor for NO3− reduction.•Phosphate removal was enhanced resulting from bio-oxidation of siderite.