Microbial community variation and functions to excess sludge reduction in a novel gravel contact oxidation reactor

Zhou

et al. 2021

Environ. Sci. Technol.

Packing carriers into the anaerobic side-stream reactor (ASSR) can enhance sludge reduction and save footprint by investigating ASSR-coupled membrane bioreactors (AP-MBRs) under different hydraulic residence times of the ASSR (HRT SR ). Three AP-MBRs and an anoxic-aerobic MBR (AO-MBR) showed efficient chemical oxygen demand (>94.2%) and ammonium nitrogen removal (>99.3%). AP-MBRs have higher (p < 0.05) total nitrogen (61.4−67.7%) and total phosphorus (57.5−63.8%) removal than AO-MBRs (47.8 and 47.7%). AP-MBRs achieved sludge reduction efficiencies of 11.8, 31.8, and 36.2% at HRT SR values of 2.5, 5.0, and 6.7 h. Packing carriers greatly improved sludge reduction under low HRT SR and is promising for accelerating sludge reduction in compact space. Metagenomic sequencing analysis showed that genes responsible for metabolism were enriched in AO-MBRs, while genes related to cellular motility and cell signaling were more abundant in the AP-MBRs. A longevity-regulating pathway showed that long lifespan provided more opportunities for worms to prey bacteria. Microscopic examination revealed that some specific protozoa (Arcella, Clathrulina, Aspidisca, Litonotus, Chiloclonella, and Vorticella) and metazoa (Rotaria and Aeolosoma hemprichi) were enriched in ASSRs. Aeolosoma hemprichi was only detected in ASSRs, and unique Cylops appeared on carriers. These results contribute to growing understanding of micrometabolic mechanisms including functional genes and microfauna-driving sludge reduction.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bacterial and Microfauna Mechanisms for Sludge Reduction in Carrier-Enhanced Anaerobic Side-Stream Reactors Revealed by Metagenomic Sequencing Analysis

Zhou

et al. 2021

Environ. Sci. Technol.

Water Environment Research

“…(band 9, 21, and 29) were the main nitrifiers in the experimental reactor responsible for nitrification. Lin et al (2009) found that the most abundant phylotypes in synthetic water treatments with gravel contact oxidation reactors are those related to the ß-Proteobacteria group, followed by those related to y-Proteobacteria and then Cytophaga-FlexibacterBacteriode. Figure 4 shows the DGGE patterns of biofilm samples taken from different modes.…”

Section: Effect Of Dissolved Oxygen On Simultaneous Nitrification Andmentioning

confidence: 98%

Evaluating the Effect of Dissolved Oxygen on Simultaneous Nitrification and Denitrification in Polyurethane Foam Contact Oxidation Reactors

Tan

et al. 2013

The effects of dissolved oxygen on simultaneous nitrification and denitrification were evaluated in polyurethane foam contact oxidation reactors in a municipal wastewater treatment process. It was observed that nitrate could be removed at low dissolved oxygen levels, but the removal rate was gradually reduced as the dissolved oxygen concentration increased to a higher level of 6.0 mg/L. Nitrogen removal remained optimal within the dissolved oxygen range of 0.5 to 1.0 mg/L. Denaturing gradient gel electrophoresis (DGGE) analysis revealed that the diversity of the microbial community changed accompanying dissolved oxygen values of 0.5 to 1.0 mg/L, 2.5 to 3.5 mg/L, 6.0 to 6.5 mg/L, and 10.0 to 12.0 mg/L, in turn, which was supported by the Shannon-Wiener index of 1.56, 1.71, 1.43, and 1.56, accordingly. Both DGGE profiling and phylogenetic analysis confirmed that the nitrifiers in reactors that are responsible for nitrification during the experiment include Nitrosospira sp., Nitrosomonas sp., and Nitrospira sp.

“…1). It was filled with highly porous carriers including natural crushed stones 3-4 cm long and 2-cm wide stuck by epoxide-resin glue into crushed stone globular aggregates (CSGA) of 10-cm total diameter (Lin et al 2009). Four aeration pipes were laid every 40 cm at the bottom of reactor.…”

Section: Experimental Design and Chemical Analysismentioning

confidence: 99%

Predicting biofilm thickness and biofilm viability based on the concentration of carbon-nitrogen-phosphorus by support vector regression

Lin

Wang

Yunlong

et al. 2015

Environ Sci Pollut Res

Self Cite

Current tools to predict biofilm thickness and viability in spatial distribution are poor, especially those based on chemical oxygen demand (COD), total nitrogen (TN), and total phosphate (TP) due to their limited data and complex calculations. Here, support vector regression (SVR) was used to predict biofilm thickness and viability in a reactor filled with carriers of crushed stone globular aggregates. Analyses combined confocal laser scanning microscopy and flow cytometry with Kriging interpolation revealed that biofilm thickness varied from 22 to 31 μm, and biofilm viability decreased from 80 to 30% in the flow direction of the reactor. The biofilm thickness at the bottom was thicker than that in the upper layer, but biofilm viability contrasted with biofilm thickness in the vertical distribution. The values of biofilm thickness and viability were predicted at a layer 35 cm from the bottom of the reactor with mean squared error values of 0.014 and 0.011, respectively. Correlation coefficients were 0.996 and 0.997 between carbon-nitrogen-phosphorus (C-N-P) removal with biofilm thickness and viability in spatial distribution, respectively. This study provided an important mathematical method to predict biofilm thickness and viability in spatial distribution based on the concentration of C-N-P.