Concentrations and distributions of fluorotelomer alcohols and perfluoroalkane sulfonamido substances in the atmosphere in the Pearl River Delta, China.

Per and polyfluoroalkyl substances (PFASs) have attracted major global concerns because some of them are environmentally persistent, bioaccumulative, and toxic. Perfluoroalkyl acids (PFAAs) have been well-characterized in water, soil, and sediment; however, fluorotelomer alcohols and perfluoroalkane sulfonamido substances have been overlooked. In this study, concentrations of three fluorotelomer alcohols and four perfluoroalkane sulfonamido substances were determined in the air at nine locations representing urban, rural-urban transect, and urban areas in the Pearl River Delta region, China to investigate their seasonal and spatial distributions and potential sources. At least two of the targeted PFASs were detected in all air samples in the Pearl River Delta region, with concentrations ranging from 371 pg/sampler to 18700 pg/sampler. Fluorotelomer alcohols were dominant compounds (contributing 46% to the ∑7PFAS concentration on average) in the atmosphere in the Pearl River Delta region. The total concentrations of the seven targeted PFASs were significantly higher in summer than in other seasons in urban areas. PFAS concentrations were positively related to the population density in the Pearl River Delta region. Local diffusive emission and long range transport could be sources of the seven PFASs in the air in the Pearl River Delta region.

Distinct microbial communities and their networks in an anammox coupled with sulfur autotrophic/mixotrophic denitrification system.

Organ carbon are often used to enhance denitrification in wastewater treatment. However, their possible effects on microbial interactions are very limited. In this work, an anaerobic ammonium oxidation (anammox) coupled with sulfur autotrophic/mixotrophic denitrification (SAD/SMD) system was used to investigate the changes in microbial interactions among the microbial communities under different nutrient condition. The removal efficiency of total nitrogen increased from 70% (SAD) to 97% (SMD). The Illumina sequencing analysis indicated that Planctomycetes was the most dominant bacterial phylum in anammox system. Thiobacillus and Sulfurimonas, two typical autotrophic denitrifiers, decreased significantly from 31.9% to 17.7%-12.2% and 9.3%, when the nutrient condition changed from SAD to SMD (P < 0.05). Meanwhile, some heterotrophic or mixotrophic denitrifying bacteria, including Gemmobacter, Pseudomonas and Thauera increased significantly (P < 0.05). Molecular ecological network (MEN) analysis showed that the addition of organic carbon substantially altered the overall architecture of the network. Compared with SAD, the SMD had shorter path lengths, indicating higher transfer efficiencies of information and materials among different microorganism. The addition of organic carbon increased the microbial interaction complexity of Proteobacteria. The links of Thiobacillus, which was a typical sulfur-oxidizing autotrophic denitrifying bacteria, significantly reduced (P < 0.05) with the addition of organic carbon, while the links of the heterotrophic bacteria Geobacter significantly increased (P < 0.05). This study provided new insights into our understanding of the shifts in the bacteria community and their microbial interactions under different nutrient conditions (SAD and SMD) in sulfur-supported denitrification system.

Effects of different potassium and nitrogen pretreatment strategies on anaerobic digestion performance of rice straw.

The effects of different potassium and nitrogen pretreatment strategies on the anaerobic digestion (AD) performance of rice straw (RS) were investigated. KOH, NH3·H2O and KOH + NH3·H2O combined pretreatments were applied. The results showed that KOH + NH3·H2O combined pretreatment achieved the highest biomethane production and TS (TS: total solid) removal rate of 274 mL g VS-1 and 43.9%, which were 6.2-75.8% and 4.3-29.5% higher than that of single alkali pretreatments and untreated RS, respectively. The NH3·H2O groups improved the process stability, which maintained the NH3-N concentration in the range of 265-580 mg L-1. It was also found that Bacteroidetes and Firmicutes were the dominant bacterial at phyla level, and the populations of acetate methanogen (Methanosarcina and Methanosaeta) were enriched in the AD system by KOH + NH3·H2O pretreatment. Furthermore, the cost of pretreatment agents can be recovered by the increased digestate nutritional value due to the K and N remaining in the digestate after AD. The results indicated that the KOH + NH3·H2O combined pretreatment might be a promising method for efficient AD of straw in future industrial applications.

Acute effects of hexavalent chromium on the performance and microbial community of activated sludge in aerobiotic reactors.

This study investigated the acute effects of hexavalent chromium (Cr(VI)) shock load at 2.5, 6 and 25 mg/L on the performance and bacterial community structures in aerobiotic activated sludge reactors. The results showed that eight-day Cr(VI) toxicity made the removal rates of COD and NH3-N to obviously decrease in all reactors. Furthermore, the higher the Cr(VI) concentration was, the more severe the influence on the whole system would be. The effect of Cr(VI) on NH3-N removal was more serious than that on COD and the function of nitrification was harder to recover. The specific oxygen uptake rate (SOUR) values dropped by 73%, 68% and 31% at 2.5, 6 and 25 mg Cr(VI)/L, respectively. The data of SOUR showed that though the concentration of Cr(VI) was low, the whole respiratory activity of bacteria was much affected. The relative abundance change of genus between the initial stage and the last showed that the bacterial community structure changed significantly. Comparing with the initial stage, the phyla of Proteobacteria, Acidobacteria and Planctomycetes were markedly reduced at the end stage. The genera of Ferruginibacter, Coxiella and Rhodanobacter were also markedly reduced. Although the performance of activated sludge can be restored at the end, the whole respiratory activity of bacteria was still at a low level according to the data of SOUR.

Effects of CeO2 nanoparticles on bacterial community and molecular ecological network in activated sludge system.

The increasing use of cerium oxide nanoparticles (CeO2 NPs) has caused concerns regarding their potential environmental risks. However, their effects on bacterial communities and network interactions in activated sludge process are still unclear. In this study, we carried out long-term exposure experiments (210 d) to investigate the influence of CeO2 NPs on wastewater treatment performance, bacterial community structure and network interactions in activated sludge systems. The results showed that long-term exposure to 1 mg/L CeO2 NPs induced the deterioration of denitrifying process, which was consistent with the inhibition of enzyme activities of nitrite oxidoreductase and nitrate reductase under CeO2 NPs. CeO2 NPs decreased the bacterial diversity and altered the overall bacterial community structure in activated sludge. Some dominant denitrifying bacteria, such as Flexibacter and Acinetobacter decreased significantly. Molecular ecological network analysis showed that CeO2 NPs decreased the network complexity of bacterial community, and probably promoted the competition in bacterial communities of activated sludge. These changes of denitrifying bacteria and the bacterial network may be relevant to the deterioration of denitrifying process. This study provides insights into how the bacteria community and their molecular ecological network respond to CeO2 NPs in activated sludge systems.