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Qian J.,Hong Kong University of Science and Technology | Lu H.,Sun Yat Sen University | Lu H.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Cui Y.,Hong Kong University of Science and Technology | And 4 more authors.
Water Research | Year: 2015

Thiosulfate, as an intermediate of biological sulfate/sulfite reduction, can significantly improve nitrogen removal potential in a biological sulfur cycle-based process, namely the Sulfate reduction-Autotrophic denitrification-Nitrification Integrated (SANI®) process. However, the related thiosulfate bio-activities coupled with organics and nitrogen removal in wastewater treatment lacked detailed examinations and reports. In this study, S2O3 2- transformation during biological SO4 2-/SO3 2- co-reduction coupled with organics removal as well as S2O3 2- oxidation coupled with chemolithotrophic denitrification were extensively evaluated under different experimental conditions. Thiosulfate is produced from the co-reduction of sulfate and sulfite through biological pathway at an optimum pH of 7.5 for organics removal. And the produced S2O3 2- may disproportionate to sulfide and sulfate during both biological S2O3 2- reduction and oxidation most possibly carried out by Desulfovibrio-like species. Dosing the same amount of nitrate, pH was found to be the more direct factor influencing the denitritation activity than free nitrous acid (FNA) and the optimal pH for denitratation (7.0) and denitritation (8.0) activities were different. Spiking organics significantly improved both denitratation and denitritation activities while minimizing sulfide inhibition of NO3 - reduction during thiosulfate-based denitrification. These findings in this study can improve the understanding of mechanisms of thiosulfate on organics and nitrogen removal in biological sulfur cycle-based wastewater treatment. © 2014 Elsevier Ltd.

Peng X.,Sun Yat Sen University | Peng X.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Jia X.,Sun Yat Sen University | Jia X.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology
Bioresource Technology | Year: 2013

The addition of different carbon and nitrogen sources can promote tetrabromobisphenol A degradation to varying degrees under co-metabolism process. A kinetic model was developed to evaluate the degradation efficiency using different carbon and nitrogen sources. Sodium formate was found to be the best carbon source for tetrabromobisphenol A degradation. The degradation rate reached 96.2% with a half-life of 4.1. d. Nitrogen supplementation can also accelerate tetrabromobisphenol A degradation. Organic nitrogen is generally better than inorganic nitrogen. A response surface methodology based on the central composite design was applied to determine the optimum conditions. It showed that concentration of sodium formate, yeast extraction, tetrabromobisphenol A, and inoculum size of microorganism were important factors, and the interaction between either of two variables played different roles. Under the optimum conditions (sodium formate 11.5. mg/L, yeast extraction 2.5. mg/L, TBBPA 1.1. mg/L and inoculum size 3.4%), TBBPA degradation rate reached the maximum. © 2013 Elsevier Ltd.

Zhao C.-M.,Sun Yat Sen University | Zhao C.-M.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Campbell P.G.C.,INRS - Institute National de la Recherche Scientifique | Wilkinson K.J.,University of Montréal
Environmental Chemistry | Year: 2016

Environmental contextThe concentration of a free metal cation has proved to be a useful predictor of metal bioaccumulation and toxicity, as represented by the free ion activity and biotic ligand models. However, under certain circumstances, metal complexes have been shown to contribute to metal bioavailability. In the current mini-review, we summarise the studies where the classic models fail and organise them into categories based on the different uptake pathways and kinetic processes. Our goal is to define the limits within which currently used models such as the biotic ligand model (BLM) can be applied with confidence, and to identify how these models might be expanded. AbstractNumerous data from studies over the past 30 years have shown that metal uptake and toxicity are often best predicted by the concentrations of free metal cations, which has led to the development of the largely successful free-ion activity model (FIAM) and biotic ligand model (BLM). Nonetheless, some exceptions to these classical models, showing enhanced metal bioavailability in the presence of metal complexes, have also been documented, although it is not yet fully understood to what extent these exceptions can or should be generalised. Only a few studies have specifically measured the bioaccumulation or toxicity of metal complexes while carefully measuring or controlling metal speciation. Fewer still have verified the fundamental assumptions of the classical models, especially when dealing with metal complexes. In the current paper, we have summarised the exceptions to classical models and categorised them into five groups based on the fundamental uptake pathways and kinetic processes. Our aim is to summarise the mechanisms involved in the interaction of metal complexes with organisms and to improve the predictive capability of the classic models when dealing with complexes. © CSIRO 2016.

Yang X.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Yang X.,Sun Yat Sen University | Shen Q.,Sun Yat Sen University | Guo W.,Sun Yat Sen University | And 2 more authors.
Chemosphere | Year: 2012

The formation of trichloronitromethane (TCNM) and dichloroacetonitrile (DCAN) was investigated during chlorination and chloramination of 31 organic nitrogen (org-N) compounds, including amino acids, amines, dipeptides, purines, pyrimidones and pyrroles. Tryptophan and alanine generated the greatest amount of TCNM during chlorination process and asparagine and tyrosine yielded the highest amount of TCNM during chloramination process. Tryptophan, tyrosine, asparagine, and alanine produced more DCAN than other org-N compounds regardless of chlorination or chloramination. TCNM and DCAN formation was higher by chlorination than by chloramination. NH 2Cl:org-N molar ratios, reaction time, and pH affected N-DBPs formation in varying degrees. TCNM and DCAN yields were usually high during chloramination of tyrosine, asparagine, and methylpyrrole under the following reaction conditions: NH 2Cl:org-N molar ratios greater than 10, reaction time for 1d, and at pH 7.2. NH 2Cl as a major nitrogen origin in TCNM and DCAN was confirmed via labeled 15N-monochloramine during chloramination of tyrosine, asparagine and methylpyrrole. In contrast, the majority of nitrogen in TCNM originated from glycine, and that in DCAN originated from pyrrole. Based on the intermediates identified by gas chromatography/mass spectrometry (GC/MS), a pathway scheme was proposed for TCNM and DCAN formation. © 2012 Elsevier Ltd.

Zhang H.,Sun Yat Sen University | Zhang H.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Guan D.,Sun Yat Sen University | Guan D.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Song M.,Huazhong Agricultural University
Forest Ecology and Management | Year: 2012

Forest plantations represent an important carbon sink. In the Pearl River Delta (PRD) in Southern China, fast-growing Eucalyptus and Acacia are favoured plantation species, but little is known regarding their efficiency with respect to biomass production, partitioning and dynamics with stand age, or the contribution made by the understory, litter and coarse woody debris (CWD) to the volume of biomass and fixed carbon. Here, a set of 21 plantations of various ages were monitored for the pattern of biomass accumulation and partitioning. A continuous biomass expansion factor (BEF) method was applied to a set of forest inventory data (FID) over the periods 1989-2003 to estimate biomass accumulation, carbon storage and its pattern of change over time. The accumulation of biomass increased with stand age, reaching, respectively, 207.45 and 189.35tha -1 in mature Eucalyptus and Acacia plantations. The contribution of secondary biomass from the understory, litter layer and CWD accounted for, respectively, up to 10.2% and 20.3% of the total biomass in the two types of plantation, highlighting the significance of secondary biomass. At a similar growth stage, the ranking of the contribution to secondary biomass in the Eucalyptus plantations was litter>herbaceous plants>shrubs>CWD, while in the Acacia plantations, it was litter>CWD>shrubs>herbaceous plants. The Eucalyptus and Acacia plantations in the PRD accumulated some 2.66-7.84Mt of biomass and sequestered 1.33-3.92Mt of carbon. For both species, the bulk of the plantations (Eucalyptus 82.1%, Acacia 89.3%) were at the young to middle-aged stage. The Acacia plantations generated a higher biomass density than the Eucalyptus plantations. Forest management intensification and reforestation programmes, especially targeting Acacia or mixed Eucalyptus/Acacia forests, offer good potential for future carbon sequestration. © 2012 Elsevier B.V.

Yang X.,Sun Yat Sen University | Yang X.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Guo W.,Sun Yat Sen University | Shen Q.,Sun Yat Sen University
Journal of Hazardous Materials | Year: 2011

Algal cells and extracellular organic matter (EOM) of two algae species, Microcystis aeruginosa (blue-green algae) and Chlorella vulgaris (green algae), were characterized. The low specific UV absorbance (SUVA) values of EOM and cells from both algae species indicated the very hydrophilic nature of algal materials. Fluorescence excitation-emission matrix showed that algal EOM and cells were enriched with protein-like and soluble microbial by-product-like matters. The formation potential of a variety of disinfection by-products (DBPs) during chlorination and chloramination of algal cells and EOM were evaluated. Algal cells and EOM of Microcystis and Chlorella exhibited a high potential for DBP formation. Yields of total DBPs varied with the algae cultivation age. Cellular materials contributed more to DBP formation than EOM. The presence of bromide led to higher concentrations of total trihalomethanes (THMs), haloacetonitriles (HANs), and halonitromethanes (HNMs). Bromide also shifted the DBPs to brominated ones. Bromine incorporation was higher in HNMs than in THMs and HANs. Compared to natural organic matter, algae under bloom seasons can contribute significantly to the DBP precursor pool. © 2011 Elsevier B.V.

Wang S.,Sun Yat Sen University | Wang S.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Liang Z.,Sun Yat Sen University
Water Research | Year: 2016

Methanogenic granular sludge from anaerobic bioreactors plays a primary role in treatment of various high-strength industrial wastewaters. The common problem of sludge floatation can lead to washout of granules from the reactor and severely affect reactor performance. However, an understanding of the specific key trigger-factors and appropriate control strategies for granular sludge floatation remains elusive. In this study, the concentration of acetate, rather than that of other volatile fatty acids (VFAs, i.e. propionate and butyrate) and granular sludge properties, was identified to be positively, linearly correlated with the amount of floating granules. The number of floating granules on propionate (18 ± 6) or butyrate-containing (34 ± 13) wastewater was comparable with that of non-VFA control wastewater (30.5 ± 7.5), and much lower than that of acetate-containing wastewater (80.5 ± 10.5). A scenario of excessive acetate-triggered granular sludge floatation is proposed based on these results as well as on the microbial community profile and spatial distribution, porous structure of granules, and impacts of operational parameters. Two new strategies, acetate-depletion and co-substrate addition, effectively reduced the number of floating granules by 28.5% and 51.6%, respectively. These results deepen our understanding of granular sludge floatation in methanogenic bioreactors and provide effective strategies to control sludge floatation. © 2016 Elsevier Ltd

Zhong Y.M.,Sun Yat Sen University | Zhong Y.M.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Jia X.S.,Sun Yat Sen University | Jia X.S.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology
World Journal of Microbiology and Biotechnology | Year: 2013

The occurrence of simultaneous anaerobic ammonia oxidation and nitrate reduction (SAD) processes by enrichment culture in the presence of glucose were clarified in batch tests. Nitrate conversion and the formation of interim by-products were investigated under autotrophic and mixotrophic conditions. Eventually, the nitrite was fully consumed and co-occurred with ammonia oxidation. The effect of penicillin G and methanol on the SAD process was also investigated. Methanol addition led to complete loss of ANAMMOX activity at concentrations as low as 1 mM. Penicillin G has little effect on the SAD process. Scanning electron microscopy (SEM) observation and denaturing gradient gel electrophoresis (DGGE) analysis revealed that ANAMMOX bacteria and co-existing bacteria are responsible for the SAD process. In conclusion, this study indicates that the ratio of nitrogen to organic carbon, and the cooperation and competition between microbes can affect the dynamics of this process. It has a potential application to remove ammonia and nitrate in the presence of organic matter by the SAD process. © 2012 Springer Science+Business Media B.V.

Yang X.,Sun Yat Sen University | Yang X.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Guo W.,Sun Yat Sen University | Lee W.,Kumoh National Institute of Technology
Chemosphere | Year: 2013

Chlorine dioxide (ClO2) is often used as an oxidant to remove taste, odor and color during water treatment. Due to the concerns of the chlorite formation, chlorination or chloramination is often applied after ClO2 preoxidation. We investigated the formation of regulated and emerging disinfection byproducts (DBPs) in sequential ClO2-chlorination and ClO2-chloramination processes. To clarify the relationship between the formation of DBPs and the characteristics of natural organic matter (NOM), changes in the properties of NOM before and after ClO2 oxidation were characterized by fluorescence, Fourier transform infrared spectroscopy (FTIR), and size and resin fractionation techniques. ClO2 preoxidation destroyed the aromatic and conjugated structures of NOM and transformed large aromatic and long aliphatic chain organics to small and hydrophilic organics. Treatment with ClO2 alone did not produce significant amount of trihalomethanes (THMs) and haloacetic acids (HAAs), but produced chlorite. ClO2 preoxidation reduced THMs, HAAs, haloacetonitriles (HANs) and chloral hydrate (CH) during subsequent chlorination, but no reduction of THMs was observed during chloramination. Increasing ClO2 doses enhanced the reduction of most DBPs except halonitromethanes (HNMs) and haloketones (HKs). The presence of bromide increased the formation of total amount of DBPs and also shifted DBPs to more brominated ones. Bromine incorporation was higher in ClO2 treated samples. The results indicated that ClO2 preoxidation prior to chlorination is applicable for control of THM, HAA and HAN in both pristine and polluted waters, but chlorite formation is a concern and HNMs and HKs are not effectively controlled by ClO2 preoxidation. © 2012 Elsevier Ltd.

Zhang W.,Sun Yat Sen University | Zhang W.,Oak Ridge National Laboratory | Zhang W.,Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology | Tsang D.C.W.,University of Canterbury | Tsang D.C.W.,Hong Kong Polytechnic University
Chemosphere | Year: 2013

Understanding the transport of metal-chelant complexes is a challenging but necessary task for assessing the in situ chelant applications for land remediation and the potential environmental risks. This study presented an integrated conceptual framework for delineating primary and secondary interactions between target metals, chelants and soil components. The mathematical transport model based on primary interactions reasonably simulated the breakthrough curves of multiple target metals (Cu, Zn, Pb, Cr, and Ni) and mineral cations (Fe, Al, Mg, Mn, and Ca) during EDTA flushing of a field-contaminated soil. The first-order extraction rates of target metals were on the order of 10-6s-1, except Zn (10-4s-1) due to exceptionally large extractable amount in the soil. These rates compared well with previously reported values for field-contaminated soil, but were much smaller than those for artificially contaminated soil. The first-order dissolution rates of mineral cations (10-6-10-5s-1) were similar to the reported values for crystalline minerals, except Ca (10-4s-1) because of substantial proton-induced dissolution of carbonates. Nevertheless, due to a wide spectrum of extraction and dissolution rates at different stages, the model provided a more conservative prediction (i.e., overestimation) of metal-chelant transport while underestimated the transport of free chelant. Further revision of the proposed model may improve its prediction accuracy but attention should be paid to the model complexity and the number of adjustable parameters. © 2013 Elsevier Ltd.

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