Phosphorus Recovery Through Vivianite Production By Carbon-based Material Enhanced Microbial Dissimilatory Iron Reduction

Due to the non-renewability and unidirectional fluidity of phosphorus,the phosphate rock resource crisis and water eutrophication have been caused.The synthesis of vivianite from sewage sludge is a promising route to solve these problems synthetically.The core mechanism of the synthesis of vivianite is the dissimilatory reduction of iron.Therefore,promoting the dissimilatory iron reduction is the key driving force for promoting the synthesis of vivianite.How to obtain high yield of crystalline products is of vital importance for the wide application of the vivianite crystallization phosphorus recovery technology.In this study,carbon-based material graphite with good conductivity was selected as an additive material to investigate the effect of graphite on the synthesis of vivianite by microbial dissimilatory iron reduction process.In this thesis,graphite was used as an external conductive carbon-based material,mixed microbes or pure microbes were used as inoculating sources,ferric citrate or ferric oxide was used as electron acceptor.The anaerobic iron-phosphorus composite system was constructed to study the effect of graphite on the synthesis of vivianite by microbial dissimilatory iron reduction process under different inoculated microorganisms and different iron forms.The experimental results showed that in the ferric citrate system inoculated with mixed bacteria,it is best for phosphorus recovery when the graphite dosage was 1 g/L and the graphite particle size was 10 ?m.Its Fe(II)content was 12% higher than the control group on the 10 th day,and the promoting effect on the synthesis of vivianite was the most obvious.In the ferric citrate system inoculated with pure bacteria,the Fe(II)content of the graphite group was 16% higher than that of the control group at 36 h.In addition,the rate of dissimilatory iron reduction and the recovery rate of phosphorus and the recovery rate of vivianite in the graphite group were higher than those in the control group.In the ferric oxide system inoculated with mixed bacteria,the Fe(II)content of the graphite group was 22% higher than that of the control group on the 15 th day.By analyzing the microbial community structure,it was found that the promotion of graphite was due to its enhanced enrichment of Geobacter.In the ferric oxide system inoculated with pure bacteria,the content of Fe(II)in the graphite group was 70% higher than that in the control group on the 30 th day.In summary,the promoting effect of graphite on the dissimilatory reduction of solid ferric iron was significantly higher than the reduction of ionic ferric iron.Regardless of whether the electron acceptor was solid ferric or ionic trivalent iron,the externally added graphite had a stronger promoting effect on the iron reduction of the pure bacterial system than the mixed bacterial system inoculated sewage.