[Effect of Chelated Iron on Nitrogen Removal Efficiency and Microbial Community Structure in the Anaerobic Ferric Ammonium Oxidation].

In order to understand the characteristics and interactions of the microbial community during the anaerobic ferric ammonium oxidation (FEAMMOX) process, this study investigated the effects of various forms of chelated iron on nitrogen removal efficiency and microbial community structure. After 77 days of reactor operation, the removal efficiency of total nitrogen was 83.32% for the ferric humate group, 43.67% for the ferric citrate group, 55.07% for the ferric sodium ethylene diamine tetraacetate group, and 12.65% for the ferric ammonium triacetate group. After the experiment, the abundance of denitrifying bacteria Comamonadaceae in ferric humate group was 17.57%, the abundance of Clostridium in ferric citrate group was 47.70%; and the abundance of denitrifying bacteria Thermomonas in the ferric sodium ethylene diamine tetraacetate group was 20.11%. This indicates that ferric humate is a more effective electron acceptor for the FEAMMOX process. The result of function prediction shows that the iron, sulfur, and nitrogen cycles are all closely related, with iron and sulfur metabolism playing an important role in nitrogen removal. In the humate group, iron respiration and the nitrogen cycle are more strongly correlated than other groups. Co-occurrence network analysis showed that the keystone species in the FEAMMOX process is Tessaracoccus.

[Stimulation of biodecolorization of direct yellow 11 by decolorization products of reactive black 5].

This study focused on the effects of decolorization products of reactive black 5 (RB5) on anaerobic decolorization of direct yellow 11 (DY11) by Rhodopseudomonas palustris W1 and its reaction mechanisms. The results showed that the decolorization products of RB5 could obviously accelerate biological decolorization rate of DY11. For initial concentration of 200 mg/L of DY11, the addition of decolorization products of RB5 resulted in that the decolorization kinetic constant K was increased from 17 mg/(L x h) to 42.5 mg/(L x h), followed by an further increase to 48.8 mg/(L x h) after optimization of RB5 supplement. Cyclic voltammogram analysis demonstrated that the decolorization products of RB5 presented electrochemical activity due to the presence of redox electron transfer mediators, as indicated by an observation of two current peaks of reversible oxidation and reduction appeared at potential of ca. 83 mV and -200 mV, respectively. According to LC-MS and FT-IR analysis, the electrochemically activated species of the decolorization products were characterized to be 7-amino-8-hydroxy-1, 2-naphthaquinone-3, 6-disulphonate-1, 2-diimine (TAHNDSDP-1). TAHNDSDP-1 with quinine-like structure was able to transfer between its oxidative and reductive forms by transferring 2[H], which was supposed to be the redox mediator to shuttle electrons from electron donors to azo dyes, thus, improving the reduction of de materials.