Elucidating Biogeochemical Reactions of Iron for Ammonium Removal and Nutrient Recovery from Wastewaters: Moving toward Sustainable Wastewater Management

Abstract

Development and applications of anaerobic treatment technologies has been discussed as an effective alternative to conventional aerobic processes for removal of nitrogen from wastewaters. With abundance of iron and its high reduction potential, employing ferric reduction-based reaction pathways in engineering processes could be an effective strategy to promote energy efficiency of wastewater treatment. In particular, ferric reduction coupled to ammonium oxidation (Feammox), a novel microbial metabolic function recently found to occur under anaerobic/anoxic condition through iron dosing, can be used for nitrogen pollutant removal. Iron dosing for wastewater treatment could also promote other microbial and chemical reactions that facilitate nutrient recovery and promote sustainability of wastewater treatment. The overarching goal of this research was to investigate the potential of developing an energy efficient iron dosed technology for nitrogen removal from wastewater employing Feammox pathway and to explore use of iron for nutrient recovery from wastewater treatment. The major research objectives include (1) developing coal mine drainage treatment and sludge disposal guidelines to facilitate production of effective sludge material for their application as iron source for wastewater treatment; (2) identifying the major knowledge gaps in using Feammox for nitrogen removal from wastewater; (3) investigating the effects of organic carbon on Feammox and abundance of Feammox bacteria; (4) examining phosphorus (P) and nitrogen (N) recovery efficiencies from sludge digestates through vivianite precipitation and membrane separation process; and (5) quantifying the efficacy of a novel ferric-dosed upflow sludge blanket bioreactor for nutrient removal and recovery from anaerobic digestates. An extensive literature review was conducted to develop coal mine drainage (CMD) treatment and sludge management guidelines, that would facilitate iron-rich sludge production with optimum characteristics for different wastewater treatment applications. A comprehensive literature review was also conducted to evaluate the potential of employing Feammox in wastewater treatment. The review identified that there is lack of knowledge regarding the effects of organic carbon or heterotrophic iron reducers (iron reducing bacteria, FeRB) on growth of Feammox microorganisms (autotrophic iron reducers). Two ferric dosed bioreactors were used to treat an ammonium containing wastewater with and without organic carbon over a 270-day period to quantify efficiencies of chemical transformations and to characterize microbial composition for comparisons. The results showed higher ammonium removal (45±5%) from wastewater containing no organic carbon compared to a lower removal efficiency (19±4%) from the wastewater with organic carbon. An increase of Feammox bacteria abundance (Acidimicrobiaceae bacterium A6) of 67% was observed in the reactor