Hongzhong Zhang

Effect of COD/N ratio on nitrogen removal and microbial communities of CANON process in membrane bioreactors.

In this study, the effect of COD/N ratio on completely autotrophic nitrogen removal over nitrite (CANON) process was investigated in five identical membrane bioreactors. The five reactors were simultaneously seeded for 1L CANON sludge and be operated for more than two months under same conditions, with influent COD/N ratio of 0, 0.5, 1, 2 and 4, respectively. DGGE was used to analyze the microbial communities of aerobic ammonia-oxidizing bacteria (AOB) and anaerobic ammonia-oxidizing bacteria (AAOB) in five reactors. Results revealed the harmonious work of CANON and denitrification with low COD concentration, whereas too high COD concentration suppressed both AOB and AAOB. AOB and AAOB biodiversity both decreased with COD increasing, which then led to worse nitrogen removal. The suppressing threshold of COD/N ratio for CANON was 1.7. CANON was feasible for treating low COD/N sewage, while the high sewage should be converted by anaerobic biogas producing process in advance.

Effect of inorganic carbon on nitrogen removal and microbial communities of CANON process in a membrane bioreactor.

In this study, a membrane bioreactor (MBR) was adopted for completely autotrophic nitrogen removal over nitrite (CANON) process. Inorganic carbon (IC) was step-wise decreased to analyze the IC influence on nitrogen removal and microbial communities, finally IC was elevated to study its recovery capability. The bioactivities of functional organisms were detected by batch experiments. Results showed that the bioactivity and biodiversity of aerobic ammonia-oxidizing bacteria (AOB) and anaerobic ammonia-oxidizing bacteria (AAOB) both decreased due to the IC shortage, while nitrite-oxidizing bacteria bioactivity showed a contrary result. When the concentration ratio of IC to nitrogen (IC/N) decreased to 1.0, the nitrogen removal sharply deteriorated, which then recovered when the ratio increased to 2.5. Denaturing gradient gel electrophoresis results showed that Nitrosomonas sp. of AOB and Candidatus Brocadia fulgida of AAOB could survive in the condition of IC deficit. The prominent IC/N ratio for high-rate and stable CANON was between 1.5-2.0.

Short-term and long-term effects of Zn (II) on the microbial activity and sludge property of partial nitrification process

Autotrophic nitrogen removal was an innovative and economical nitrogen removal technology with less oxygen and no organics consumption, in which partial nitrification (PN) is the key component. It is necessary to clear the impact of metal ions on PN since the development of industry increased their opportunity for entering into wastewater. In this study, PN process was successfully started-up in an SBR, the short-term and long-term effects of Zn (II) on microbial bioactivity and the sludge adsorption ability for Zn (II) were investigated. Results suggested that low Zn (II) were favorable for AOB bioactivity, while the long-term effect also induced NOB bioactivity. The suppression threshold of Zn (II) on AOB in short-term effect was 10mgL-1, which rose to 50mgL-1 in the long-term effect due to the self-adaption. The PN sludge presented prominent absorbability for zinc and performed a quadratic relation with the Zn (II) concentration.

Chronic impacts of TiO 2 nanoparticles on Populus nigra L. leaf decomposition in freshwater ecosystem

Titanium dioxide (TiO2) nanoparticles have been applied in diverse commercial products, which could lead to toxic effects on aquatic microbes and would inhibit some important ecosystem processes. The study aimed to investigate the chronic impacts of TiO2 nanoparticles with different concentrations (5, 50, and 500 mg L-1) on Populus nigra L. leaf decomposition in the freshwater ecosystem. After 50 d of decomposing, a significant decrease in decomposition rates was observed with higher concentrations of TiO2 nanoparticles. During the period of litter decomposition, exposure of TiO2 nanoparticles led to decreases in extracellular enzyme activities, which was caused by the reduction of microbial especially fungal biomass. In addition, the diversity and composition of the fungal community associated with litter decomposition were strongly affected by the concentrations of TiO2 nanoparticles. The diversity and composition of the fungal community associated with litter decomposition was strongly affected. The abundance of Tricladium chaetocladium decreased with the increasing concentrations of TiO2 nanoparticles, indicating the little contribution of the species to the litter decomposition. In conclusion, this study provided the evidence for the chronic exposure effects of TiO2 nanoparticles on the litter decomposition and further the functions of freshwater ecosystems.

Effect of Fe (II) in low-nitrogen sewage on the reactor performance and microbial community of an ANAMMOX biofilter

In this study, the effect of Fe (II) on Anaerobic Ammonium Oxidation (ANAMMOX) process was investigated by step-wise increasing the Fe (II) in influent from 1 to 50 mg L-1. The nitrogen removal, biofilm property and the microbial community were analyzed in each phase. Results showed that, the anaerobic ammonia-oxidizing bacteria (AAOB) bioactivity and the nitrogen removal of ANAMMOX system were slightly improved to 0.58 from the initial 0.51 kg m-3 d-1 by Fe (II) in 1-5 mg L-1. The nitrogen removal was suppressed and could recover to the initial level during the same period under 10-20 mg L-1 Fe (II), while it did not recover to the initial level under 30 mg L-1 Fe (II) and showed no recovery performance under 50 mg L-1 Fe (II). The irreversible suppression threshold of Fe (II) was calculated as 50 mg L-1. The iron content in ANAMMOX biofilm presented linear correlation with the influent Fe (II) in 1-20 mg L-1, which then tended to be stable when Fe (II) was higher. Dehydrogenase activity (DHA) showed similar and faster response to Fe (II) than the microbial activity, and it was an effective pre-indicator for the nitrogen removal performance in the ANAMMOX system suffered Fe (II). The Fe (II) feeding firstly led to the relative abundance of AAOB decreased to 11.04% from the initial 35.46%, and finally picked up to 19.39% after the long-term acclimatization.

Harmful effect of nanoparticles on the functions of freshwater ecosystems: Insight into nanoZnO-polluted stream

ZnO nanoparticle toxicity on aquatic organisms has been extensively studied, but its concentration-and time-dependent effects on ecosystem functioning are remain uncertain. Here we assessed the harmful effects of nano-ZnO (10, 100, 1000 mg L-1) on the stream functioning by using a microcosm system simulating poplar leaf decomposition for 50 days. The 100 mg L-1 ZnO nanoparticles had significantly and stably inhibitory effect on the litter decomposition during the exposure period. The inhibition was not detected in the 10 mg L-1 treatment until 43 d. In contrast, the significant and continuous inhibition started to disappear from 43 d in the 1000 mg L-1 treatment. The varied consequences on litter decomposition might be directly affected by the different ZnO nanoparticle homogeneity of the different treatments. ZnO nanoparticles led to significant decreases in pH value of the decomposition environment, which had significant and positive relationships to the activities of dehydrogenase, glycine-aminopeptidase, N-acetylglucosaminidase, and acid phosphatase. Besides, 10 and 1000 mg L-1 ZnO nanoparticles led to lower fungal diversity, which was negatively related to the variability of decomposition. In conclusion, fungal decomposers showed different responses to the different concentrations of ZnO nanoparticle, and ultimately affected the stability of ecosystem functions.

Effects of biochar on the microbial activity and community structure during sewage sludge composting

To explore the contributions of functional bacterial community in composting, we performed medium-scale composting of sewage sludge and sawdust mixtures amended with rice straw biochar at different dosages (5, 10, and 20% of fresh mixture weight) in 400 L bioreactor systems. The dynamics of enzyme activity and bacterial community composition were monitored during the composting. The addition of biochar above 10% inhibited the activity of protease but promoted the activities of cellulase and peroxidase, which also increased the fluctuation of bacterial diversity during the composting. The relationship between the activity of most enzymes and bacterial community was strengthened by the addition of biochar (10% and 20%), which further enhanced the contributions of the functional bacterial communities to composting. Therefore, the study provides evidence for the promoting effects of biochar on the functions of bacterial community.

Effect of inorganic carbon concentration on the stability and nitrite-oxidizing bacteria community structure of the CANON process in a membrane bioreactor

ABSTRACT In the completely autotrophic nitrogen removal over nitrite (CANON) process, the nitrite-oxidizing bacteria (NOB) should be effectively suppressed or thoroughly washed out. In this study, the nitrate production and the structure of NOB community under different inorganic carbon (IC) concentrations were investigated using denaturing gradient gel electrophoresis (DGGE) in a membrane bioreactor (MBR). Results showed that IC decrease correspondingly lowered the nitrogen removal, and simultaneously induced the nitrate production by NOB. DGGE results indicated the IC deficit led to the biodiversity increasing of both Nitrobacter-like NOB and Nitrospira-like NOB. An equation fitted between the ratio of nitrate production to ammonia consumption () and the ratio of influent IC to ammonia concentration () indicated the influent should be controlled between 1.6 and 2.3 to ensure the stable operation of the CANON process. A small amount addition of organic material could be used as an effective strategy to suppress NOB when the ratio was not appropriate.

Degradation of organophosphate esters in sewage sludge: Effects of aerobic/anaerobic treatments and bacterial community compositions

This dataset provides detail information on the analytical methods of organophosphate esters (OPEs) in sludge samples, including the sample preparation, ultra-high performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) analysis, quality assurance and quality control (QA/QC). The concentration of target OPE compounds in collected samples of four individual treatment was provided, including aerobic composting combined with pig manure (T1), aerobic composting without pig manure (T2), anaerobic digestion combined with pig manure (T3), and anaerobic digestion without pig manure (T4). To investigate the variation of bacterial community compositions, principal components analysis (PCA) was provided based on the high-throughput sequencing. These data would be useful for clarifying the removal of OPEs under aerobic and anaerobic conditions. Besides, it also provides important information on the potential bacterial strains responsible for the biodegradation of OPEs in each treatment.

Polymeric ionic liquid based fused silica fiber by chemical binding for headspace solid-phase microextraction of organophosphate esters in water samples

ABSTRACT In this paper, a convenient method was developed for preparing polymeric ionic liquid based fiber coating onto a fused silica fiber by using covalent bonding for headspace solid-phase microextraction of five organophosphorus esters from real water samples. 1-vinyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium chloride was anchored on the silica layer by covalent bonding and then the polymeric ionic liquid layer was formed via free radical copolymerization with vinyl-substituted imidazolium in the presence of azobisisobutyronitrile as initiator. The limits of detection ranged from 0.68 to 100 ng L−1. The intra- and inter-day precisions, evaluated by relative standard deviation, were in the range of 4–8% and 1–10%, respectively. The recoveries of spiked real water samples were in the range of 73–110% and 77–118%, respectively, at two different concentration levels.