Iron-retrofitted anaerobic baffled reactor system for rural wastewater treatment: Stable performance of nutrients removal with phosphorus recovery and minimal sludge production.

An iron-retrofitted anaerobic baffled reactor (ABR) system was developed for the effective treatment of rural wastewater with reduced maintenance demand and aeration costs. Average removal efficiencies of chemical oxygen demand, total nitrogen and total phosphorus of 99.4%, 62.7% and 92.6% were achieved respectively, when the ABR system was operating at steady state. With effective bioreduction of Fe ^III in the anaerobic chambers, phosphorus was immobilized in the sludge as vivianite, the sole phosphorus-carrying mineral. The Fe ^III in the recirculated sludge induced Feammox in the ABR reactor, contributing 14.8% to total nitrogen removal. Biophase separation and enrichment of microorganisms associated with iron and nitrogen transformations were observed in the system after Fe dosing, which enhanced the removal of pollutants. The coupling of Feammox and vivianite crystallization to remove nitrogen and phosphorus in an iron-retrofitted ABR would appear to be a promising technology for rural wastewater treatment.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Xiang Cheng reports financial support was provided by National Key Research and Development Program of China. Xiang Cheng reports financial support was provided by Natural Science Foundation of China. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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