Sen Wang

Long-term effects of ZnO nanoparticles on nitrogen and phosphorus removal, microbial activity and microbial community of a sequencing batch reactor

The performance, microbial activity, and microbial community of a sequencing batch reactor (SBR) were investigated under the long-term exposure of ZnO nanoparticles (ZnO NPs). Low ZnO NPs concentration (less than 5mg/L) had no obvious effect on the SBR performance, whereas the removals of COD, NH4(+)-N, and phosphorus were affected at 10-60mg/L ZnO NPs. The variation trend of nitrogen and phosphorus removal rate was similar to that of microbial enzymatic activity with the increase of ZnO NPs concentrations. The richness and diversity of microbial community showed obvious variations at different ZnO NPs concentrations. ZnO NPs appeared on the surface and cell interior of activated sludge, and the Zn contents in the effluent and activated sludge increased with the increase of ZnO NPS concentration. The present results provide use information to understand the effect of ZnO NPS on the performance of wastewater biological treatment systems.

Performance evaluation, microbial enzymatic activity and microbial community of a sequencing batch reactor under long-term exposure to cerium dioxide nanoparticles

The performance, microbial enzymatic activity and microbial community of a sequencing batch reactor (SBR) were investigated under long-term exposure to cerium dioxide nanoparticles (CeO2 NPs). The COD removal kept a stable value at 0-5mg/L CeO2 NPs and then decreased at 10-60mg/L CeO2 NPs. The NH4(+)-N removal had no obvious changes at 0-30mg/L CeO2 NPs, and a minor decrease appeared at 60mg/L CeO2 NPs. Compared to 0mg/L CeO2 NPs, the phosphorus removal showed a decrease at 2mg/L CeO2 NPs and slightly increased at 5-60mg/L CeO2 NPs. The nitrogen and phosphorus removal rates had similar variation trends to the microbial enzymatic activities. The variations of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) indicated that high CeO2 NPs concentration could result in the biotoxicity to activated sludge. The presence of CeO2 NPs had obvious effect on the microbial richness and diversity of activated sludge.

The effects of divalent copper on performance, extracellular polymeric substances and microbial community of an anoxic–aerobic sequencing batch reactor

The effects of divalent copper (Cu(II)) on the performance, extracellular polymeric substances (EPS) and microbial community of activated sludge were investigated in an anoxic–aerobic sequencing batch reactor (SBR). The removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) decreased with the increase of influent Cu(II) concentration from 0 to 50 mg L−1. The specific oxygen utilization rate (SOUR), specific ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR), and specific nitrate reduction rate (SNRR) decreased with the increase of influent Cu(II) concentration. The protein (PN) contents in the loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) increased from 3.67 and 4.73 mg g−1 VSS to 32.83 and 50.45 mg g−1 VSS with the increase of influent Cu(II) concentration from 0 to 50 mg L−1, respectively. The polysaccharide (PS) contents in the LB-EPS and TB-EPS increased from 1.44 and 2.68 mg g−1 VSS to 8.51 and 19.84 mg g−1 VSS with the increase of influent Cu(II) from 0 to 50 mg L−1, respectively. The three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectra and Fourier transform infrared (FTIR) spectra illustrated that the addition of Cu(II) to the influent had distinct effects on the functional groups of PN and PS in the LB-EPS and TB-EPS. The sludge volume index (SVI) showed a negative correlation with LB-EPS (or TB-EPS) content at different Cu(II) concentrations. Some microorganisms adapting to high Cu(II) concentration became predominant bacteria, while others without Cu(II)-tolerance capacity gradually depleted or weakened with the increase in Cu(II) concentration.

Effect of oxytetracycline on performance and microbial community of an anoxic–aerobic sequencing batch reactor treating mariculture wastewater

The performance and microbial community of an anoxic–aerobic sequencing batch reactor (SBR) treating mariculture wastewater were evaluated at different oxytetracycline (OTC) concentrations. The COD and nitrogen removal efficiencies decreased with the increase in OTC concentration from 0 to 12 mg L−1. No apparent NO3−-N accumulation was found during the whole operational period, whereas NO2−-N accumulation occurred at 12 mg L−1 OTC. The specific oxygen uptake rate (SOUR), specific ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR) and specific nitrate reduction rate (SNRR) decreased with increasing influent OTC concentration. The protein (PN) and polysaccharide (PS) contents in the loosely-bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS) increased with the increase in OTC concentration from 0 to 12 mg L−1, respectively. The appearance of OTC in the influent could obviously affect the functional groups of the PN and PS in the LB-EPS and TB-EPS. X-ray photoelectron spectroscopy (XPS) illustrated that amino, carboxyl and hydroxyl groups in the EPS might be involved in the interaction between the EPS and OTC. The denaturing gradient gel electrophoresis (DGGE) profile indicated that some variations were found in the microbial community of the activated sludge with increasing OTC concentration. Some microorganisms were depleted or weakened with the increase in OTC concentration, whereas others became the predominant microorganisms due to their ability to adapt to the OTC toxicity.

Effects of salinity on performance and microbial community structure of an anoxic-aerobic sequencing batch reactor

The effects of salinity on the performance and microbial community structure of activated sludge were investigated in an anoxic-aerobic sequencing batch reactor (SBR). The removal efficiencies of chemical oxygen demand (COD) and -N decreased as the influent salinity increased from 0.5% to 6%. The specific oxygen utilization rate of activated sludge increased from 22.47 to 43.16 mg O2 g−1 mixed liquid suspended solids (MLSS) h−1 with the increase in salinity from 0.5% to 4% and subsequently decreased to 18.3 mg O2 g−1 MLSS h−1 at 6% salinity. The specific ammonium oxidation rate (SAOR) and specific nitrite oxidation rate (SNOR) decreased slowly at 0.5–1% salinity and then decreased rapidly with the increase in salinity from 1% to 6%. The SNOR diminished at a faster rate than the SAOR with the increase in salinity from 0.5% to 6%. The specific nitrate reduction rate (SNRR) decreased with the increase in salinity, whereas the SNRR was higher than the sum of SAOR and SNOR at 0.5–6% salinity. The denaturing gradient gel electrophoresis profiles revealed obvious changes in microbial community structure at different salinities. Some microbes were capable of tolerating up to 6% salinity in the SBR, such as Planomonospora sphaerica, Nitrosomonas sp. Is32, and Denitromonas sp. D2–1.

Effect of florfenicol on performance and microbial community of a sequencing batch biofilm reactor treating mariculture wastewater

ABSTRACT The effects of florfenicol (FF) on the performance, microbial activity and microbial community of a sequencing batch biofilm reactor (SBBR) were evaluated in treating mariculture wastewater. The chemical oxygen demand (COD) and nitrogen removal were inhibited at high FF concentrations. The specific oxygen utilization rate (SOUR), specific ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR) and specific nitrate reduction rate (SNRR) were decreased with an increase in the FF concentration from 0 to 35 mg/L. The chemical compositions of loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS) could be affected with an increase in the FF concentration. The high-throughput sequencing indicated some obvious variations in the microbial community at different FF concentrations. The relative abundance of Nitrosomonas and Nitrospira showed a decreasing tendency with an increase in the FF concentration, suggesting that FF could affect the nitrification process of SBBR. Some genera capable of reducing nitrate to nitrogen gas could be inhibited by the addition of FF in the influent, such as Azospirillum and Hyphomicrobium.