Towards a better understanding of the anaerobic/oxic/anoxic-aerobic granular sludge process (AOA-AGS) for simultaneous low-strength wastewater treatment and in situ sludge reduction from ambient to winter temperatures.

The new anaerobic/oxic/anoxic-aerobic granular sludge (AOA-AGS) merits the advantages of effective carbon utilization and low-carbon treatment. However, low temperature poses stressing concerns and the resisting mechanism remains much unknown. Herein, an AOA-AGS process was configured for simultaneous nitrification, denitrification and phosphorus removal (SNDPR) with low-strength wastewater from ambient (>15 °C) to winter temperatures (<15 °C). Results showed that simultaneously advanced nutrients removal, and dramatic in situ sludge reduction (Yobs of 0.093 g MLSS/g COD) were gained regardless of seasonally decreasing temperatures. Winter temperatures even amplified Candidatus Competibacter predominating from 20.11% to 34.74%, which laid the core basis for endogenous denitrification, sludge minimization and temperature resistance. A removal model was thus proposed given the observed functional groups, and doubts were also raised for future investigations. This study would aid a better understanding on the microbial ecology and engineering aspects of the new AOA-AGS process treating low-strength wastewater at low temperatures.

Advanced low-strength wastewater treatment, side-stream phosphorus recovery, and in situ sludge reduction with aerobic granular sludge.

Modern paradigm has upgraded wastewater treatment plants (WWTPs) to water resources recovery facilities (WRRFs), where aerobic granular sludge (AGS) is a sewage treatment technology with promising phosphorus recovery (PR) potential. Herein, the AGS-based simultaneous nitrification, denitrification, and phosphorus removal coupling side-stream PR process (AGS-SNDPRr) was developed with municipal wastewater. Results revealed that AGS always maintained good structural stability, and pollutant removal was unaffected and effective after 40 days of anaerobic phosphorus-rich liquid extraction (fixed rate of 30%). The AGS-SNDPRr achieved a stable phosphorus recovery efficiency of 63.40%, and the side-stream PR further exaggerated in situ sludge reduction by 7.7-10%. Apart from responses of extracellular polymeric substances (EPS), the Matthew effect of typical denitrifying glycogen accumulating organisms (DGAOs) Candidatus_Competibacter up to 67.40% mainly contributed to enhanced performance of this new process. This study demonstrated a new approach for simultaneous advanced wastewater treatment, phosphorus recovery, and excess sludge minimization.

Performance of anaerobic/oxic/anoxic simultaneous nitrification, denitrification and phosphorus removal system overwhelmingly dominated by Candidatus_Competibacter: Effect of aeration time.

The anaerobic/oxic/anoxic simultaneous nitrification, denitrification and phosphorus removal process (AOA-SNDPR) is a promising technology for enhanced biological wastewater treatment and in situ sludge reduction. Herein, effects of aeration time (90, 75, 60, 45, and 30 min, respectively) on the AOA-SNDPR were evaluated including simultaneous nutrients removal, sludge characteristics, and microbial community evolution, where the role of a denitrifying glycogen accumulating organisms, Candidatus_Competibacter, was re-explored given its overwhelming dominance. Results revealed that nitrogen removal was more vulnerable, and a moderate aeration period of 45-60 min favored nutrients removal most. Low observed sludge yields (Yobs) were obtained with decreased aeration (as low as 0.02-0.08 g MLSS/g COD), while MLVSS/MLSS got increased. The dominance of Candidatus_Competibacter was identified as the key to endogenous denitrifying and in situ sludge reduction. This study would aid the low carbon- and energy-efficient aeration strategy for AOA-SNDPR systems treating low-strength municipal wastewater.

Scale-dependent effects of species diversity on aboveground biomass and productivity in a subtropical broadleaved forest on Mt. Huangshan.

The relationship between species diversity and biomass/productivity is a major scientific question in ecology. Exploring this relationship is essential to understanding the mechanisms underpinning the maintenance of biodiversity. Positive, negative, and neutral relationships have been identified in controlled experiments and observational research. However, increasing evidence suggests that the effects of species diversity on aboveground biomass and productivity are influenced by biotic and abiotic factors, but it remains unclear whether scale-dependent effects affect aboveground biomass and productivity. Herein, we used a generalized linear regression model and a structural equation model to explore relationships between species diversity and productivity/aboveground biomass under different scales and to investigate the effects of topographical factors and species diversity on ecosystem functioning. The results revealed a positive relationship between biodiversity and ecosystem functioning based on species diversity and aboveground biomass. Different sampling scales may impact the relationship between species diversity and ecosystem functioning. A positive relationship was found between species richness and productivity at medium and large scales; however, ambiguous relationships were found in productivity and other species diversity indices. Elevation was a key factor affecting both biomass and productivity. These results suggest that species diversity is not the only factor affecting biomass and productivity, and the positive correlation between species diversity and ecosystem functioning is mediated by abiotic factors.

The complete chloroplast genome of Rhododendron shanii W.P. Fang (Ericaceae), a endemic plant from the Southern Dabie Mountains of China.

Rhododendron shanii W.P. Fang 1983 (Ericaceae) is woody plant naturally distributed in the southwest of Anhui, China. The complete chloroplast genome sequence of R. shanii was generated by whole-genome next-generation sequencing data and assembled based on three Rhododendron species chloroplast genome. The complete chloroplast genome sequence of R. shanii was 204,170 bp and divided into four distinct regions: small single-copy region (2615 bp), large single-copy region (107,189 bp), and a pair of inverted repeat regions (47,183 bp). The genome annotation displayed 150 genes, including 95 protein-coding genes, 47 tRNA genes, and eight rRNA genes. Phylogenetic analysis with the Ericaceae reported chloroplast genomes revealed that R. shanii is sister to the clade comprising R. delavayi, R. griersonianum and R. platypodum.

Pyrite-Based Autotrophic Denitrifying Microorganisms Derived from Paddy Soils: Effects of Organic Co-Substrate Addition.

The presence of organic co-substrate in groundwater and soils is inevitable, and much remains to be learned about the roles of organic co-substrates during pyrite-based denitrification. Herein, an organic co-substrate (acetate) was added to a pyrite-based denitrification system, and the impact of the organic co-substrate on the performance and bacterial community of pyrite-based denitrification processes was evaluated. The addition of organic co-substrate at concentrations higher than 48 mg L-1 inhibited pyrite-based autotrophic denitrification, as no sulfate was produced in treatments with high organic co-substrate addition. In contrast, both competition and promotion effects on pyrite-based autotrophic denitrification occurred with organic co-substrate addition at concentrations of 24 and 48 mg L-1. The subsequent validation experiments suggested that competition had a greater influence than promotion when organic co-substrate was added, even at a low concentration. Thiobacillus, a common chemolithoautotrophic sulfur-oxidizing denitrifier, dominated the system with a relative abundance of 13.04% when pyrite served as the sole electron donor. With the addition of organic co-substrate, Pseudomonas became the dominant genus, with 60.82%, 61.34%, 70.37%, 73.44%, and 35.46% abundance at organic matter concentrations of 24, 48, 120, 240, and 480 mg L-1, respectively. These findings provide an important theoretical basis for the cultivation of pyrite-based autotrophic denitrifying microorganisms for nitrate removal in soils and groundwater.

Distinct responses of aerobic granular sludge sequencing batch reactors to nitrogen and phosphorus deficient conditions.

The nutrients availability determines efficiency of biological treatment systems, along with the structure and metabolism of microbiota. Herein nutrients deficiencies on aerobic granular sludge were comparatively evaluated, treating wastewater with mass ratios of chemical oxygen demand : nitrogen : phosphorus being 200:20:4, 200:2:4, and 200:20:0.4 (deemed as nutrient-balanced, nitrogen-deficient, and phosphorus-deficient), respectively. Results revealed that both nitrogen and phosphorus deficiencies significantly raised the effluent qualities especially nitrogen removal. However, nitrogen deficiency aroused considerable growth of filamentous bacteria, while granules kept compact structure under phosphorus deficient condition. Extracellular polymeric substances (EPS) also varied in contents and structures in response to different wastewaters. Microbial community structure analysis demonstrated that nitrogen deficiency led to lower richness and higher diversity, while the reverse was observed under phosphorus deficient condition. Nitrogen deficiency mainly induced decrease of nitrifying bacteria, while similarly phosphorus deficiency led to loss of phosphorus accumulating organisms. Dramatic enrichment Candidatus_Competibacter and filamentous Thiothrix were found under nutrients deficiencies, in which the latter explained and indicated filamentous bulking potential especially under nitrogen limited condition. Bacterial metabolism patterns verified the functions of microbial community responding to nutrients via PICRUSt2 prediction mainly by up-regulating cell motility, and cellular processes and signaling. This study could aid understanding of long-term stability of aerobic granular sludge for low-strength wastewater treatment.

The performance of pyrite-based autotrophic denitrification column for permeable reactive barrier under natural environment.

The effect of temperature on pyrite-based autotrophic denitrification performance and conversion between N species under natural conditions was investigated by using dynamic-flow column experiment. Phosphate and bicarbonate were added trying to enhance denitrification performance when the temperature decreased to 20 °C. However, the temperature had a much more sensitive influence on the denitrification process than substances addition. NO3--N removal efficiency decreased with the decrease of temperature. When the temperature was higher than 20 °C, the NO2--N reduction process was more sensitive to the temperature drop, while the process of NO3--N to NO2--N was more sensitive to temperature drop when the temperature was lower than 20 °C. The different influence of temperature drop on the two processes led to changes of the distribution of NO3--N, NO2--N, and SO42--S along the column. However, the electron contribution of pyrite among the electron donors only changed slightly.

Photoelectric properties of TiO2-ZrO2 thin films prepared by sol-gel method.

Acidic sols of TiO2, ZrO2 and Ti-Zr mixed oxide precursors were prepared. The sols were then smeared on quartz substrate and annealed at 650 degrees C for 2 hour to form polycrystalline oxide films. XRD, SEM, UV-visible absorption spectra and XPS were carried out to characterize the films. It was found that the crystalline phase of pure titania is an anatase and pure zirconia is a tetragonal. The binary oxides show the anatase phase at the molar ratio of Ti:Zr = 2.73:1, which means that solid solution was formed. The absorption edge of the TiO2-ZrO2 binary oxides showed obvious blue shift as the Zr ratio increased. The results obtained indicate that the band gap of the binary oxides could be adjusted from 3.2 eV (TiO2) to 7.8 eV (ZrO2) by varying the molar ratio of Ti and Zr. Au interdigitated electrodes were produced by planar technology and MSM (metal-semiconductor-metal) structure UV detector based on TiO2-ZrO2 binary oxides was fabricated. Obvious photoelectric response was observed.