Difference and Network Analysis of Functional Genes Revealed the Hot Area of Carbon Degradation, Nitrogen, Phosphorus, and Sulfur Cycling in Blending Systems with Pyrite and Poly(3-hydroxybutyrate-hydroxyvalerate) for Nitrogen and Phosphorus Removal

Abstract

A higher denitrification rate was realized via controlling the mass ratio of pyrite and poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) under natural aerobic conditions. The results showed that the suitable mass ratio of PHBV and pyrite could be 1:2 with its removal efficiency of nitrogen and phosphorus of 99.7 and 53.4%, respectively. The PHBV/pyrite system has formed the spatial patterns of the biofilm community, such as Dechloromons attached to the pyrite surface, Rhodocyclaceae attached to the PHBV surface, and Acidovorax attached to the suppled sludge, which highlighted that the autotrophic− heterotrophic synergy was achieved. The difference analysis among functional genes detected by high-throughput quantitative polymerase chain reaction indicated that the surface of pyrite in the pyrite/PHBV system is the hot area of methane production, the denitrifying process, and phosphorus removal. Network analysis indicated that there was a closer connection among functional genes on the pyrite surface, also supporting the speculation that pyrite was the hot area for the interaction of various genes in the pyrite/PHBV system. The key gene co-occurrence revealed that lig, nirS, and aspA are the keystone genes for cellulose degradation, denitrification, and S cycling, respectively. These results suggested that the pyrite surface was the hot area for denitrification, phosphorus removal in the blending system with pyrite and PHBV for nitrogen and phosphorus removal.

Significantly Enhanced Nitrate and Phosphorus Removal by Pyrite/Sawdust Composite-Driven Mixotrophic Denitrification with Boosted Electron Transfer: Comprehensive Evaluation of Water–Gas–Biofilm Phases during a Long-Term Study

“…These authors reported the coexistence of autotrophic denitrifiers such as Thiobacillus (20.3%) and heterotrophic denitrifiers such as Anaerolineaceae (6.0%). We previously reported that Thiobacillus and Acidovorax were enriched on pyrite and poly-3-hydroxybutyrate-hydroxyvalerate (PHBV) surfaces, respectively, in a simple blend of pyrite and PHBV in a mixotrophic denitrification system. , However, pyrite is too large to give full play to the potential of pyrite-based autotrophic denitrification in the above-mentioned pyrite-based mixotrophic denitrification systems, and pyrite is chemically oxidized by direct exposure to air, leading to massive consumption of pyrite and high sulfate accumulation …”

“…Tight microbial interactions between autotrophs and heterotrophs in the mixotrophic denitrification system help to improve the system’s stability and thus optimize nitrogen removal performance . Among mixotrophic denitrification systems, pyrite-based mixotrophic denitrification has gained the most research attention, which relies on coupling sulfur-based autotrophic denitrifying bacteria with heterotrophic denitrifying bacteria. ,− For instance, Jin et al constructed a simple blend of pyrite and sawdust to form a mixotrophic denitrification system, which achieved high NO 3 – –N removal rates of 19.3 ± 1.8 g N/m 3 /d. These authors reported the coexistence of autotrophic denitrifiers such as Thiobacillus (20.3%) and heterotrophic denitrifiers such as Anaerolineaceae (6.0%).…”