Phosphate removal from landfill leachate using ferric iron bioremediation under anaerobic condition

Landfill leachates contain a variety of contaminants including phosphorus, whose entry into the surface waters should be restricted given the eutrophication risks. In this study, we investigated the utility of the ferric iron bioreduction process to remove phosphorus from municipal landfill leachate. An anaerobic bioreduction experiment was conducted in diluted leachate (1:5), in the presence of Shewanella sp. (10(8) cell mL(-1)). Two iron minerals, hematite (H) and nontronite (NAU-2) were also employed as Fe(III) sources. Serial sampling was carried out during incubation at 0, 2, 5, 10, 15, 20, 25, and 30 days. The results confirmed that bioreduction of Fe(III) occurred in the presence of both iron minerals but more extensively in the presence of NAU-2. Phosphate was precipitated chemically as struvite during the first days of the experiment, correlated to the high initial concentrations of ammonium and magnesium in the leachate. Subsequently, phosphate removal was shown to be proportional to biological Fe(II) generation and creating the conditions for precipitation of vivianite. Overall, phosphate removal from leachate in suspensions containing hematite or NAU-2 was 83 and 86%, respectively.

Automated summary

The study showed that bioreduction of Fe(III) was more extensive in the presence of nontronite compared to hematite, leading to better removal of phosphate from leachate. Phosphate was initially precipitated as struvite in the experiment, with subsequent removal being proportional to biological Fe(II) generation. Overall, phosphate removal in suspensions containing hematite or nontronite was 83% and 86%, respectively.