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Featured researches published by Hangzhou Xu.


Chemosphere | 2015

Allelopathic effects of Ailanthus altissima extracts on Microcystis aeruginosa growth, physiological changes and microcystins release

Panpan Meng; Haiyan Pei; Wenrong Hu; Zhongde Liu; Xiuqing Li; Hangzhou Xu

The use of allelochemicals has been proved an environmentally friendly and promising method to control harmful algal blooms. This study was conducted to explore the application potential of Ailanthus altissima (A. altissima) extracts in Microcystis aeruginosa (M. aeruginosa) control for the first time. Four treatments with A. altissima extractions (25mgL(-1), 50mgL(-1), 100mgL(-1), and 200mgL(-1) respectively) and a control group were built to investigate the effects of A. altissima on the growth, cellular microstructure and cell viability, physiological changes, and release of extracellular matters. Results showed that the cell density of M. aeruginosa was effectively inhibited by A. altissima extract, and the inhibition rates were dose-dependent within 5d. Especially for the treatment with 200mgL(-1) of extract, the inhibitory rates remains above 90% after 5d exposure. In addition, A. altissima effectively decreased the amount of extracellular cyanotoxin microcystins and destroyed the photosynthesis-related structure of algae cell during the experimental period. The results demonstrated the A. altissima extracts can be used as an effective and safe algicide to control algal blooms. However, it must be noted that specific compounds responsible for algicidal effect should be isolated and identified to explore inhibition mechanism of A. altissima in future study.


Science of The Total Environment | 2017

A promising application of chitosan quaternary ammonium salt to removal of Microcystis aeruginosa cells from drinking water

Yan Jin; Haiyan Pei; Wenrong Hu; Yaowen Zhu; Hangzhou Xu; Chunxia Ma; Jiongming Sun; Hongmin Li

This work was aimed toward studying the new application of chitosan quaternary ammonium salt (HTCC), a water-soluble chitosan derivative, on removal of Microcystis aeruginosa (M. aeruginosa) cells during HTCC coagulation and floc storage. Results showed that all cells were removed without damage under optimum coagulation conditions: HTCC dosage 1.5mg/L, rapid mixing for 0.5min at 5.04g and slow mixing for 30min at 0.20g. The high removal efficiency was due to the large size and compact structure of flocs formed by HTCC, which readily settled. During floc storage, HTCC could induce production of reactive oxygen species (ROS), which would accelerate M. aeruginosa cell lysis. But the flocs, into which the cells aggregated, could protect cells from cellular oxidative damage caused by ROS, thus keeping the cells intact for a longer time.


Scientific Reports | 2016

Behaviors of Microcystis aeruginosa cells during floc storage in drinking water treatment process.

Hangzhou Xu; Haiyan Pei; Hongdi Xiao; Yan Jin; Xiuqing Li; Wenrong Hu; Chunxia Ma; Jiongming Sun; Hongmin Li

This is the first study to systematically investigate the different behaviors of Microcystis aeruginosa in the sludges formed by AlCl3, FeCl3, and polymeric aluminium ferric chloride (PAFC) coagulants during storage. Results show that the viability of Microcystis aeruginosa in PAFC sludge was stronger than that of cells in either AlCl3 or FeCl3 sludge after the same storage time, while the cells’ viability in the latter two systems stayed at almost the same level. In AlCl3 and FeCl3 sludges high concentrations of Al and Fe were toxic to Microcystis aeruginosa, whereas in PAFC sludge low levels of Al showed little toxic effect on Microcystis aeruginosa growth and moderate amounts of Fe were beneficial to growth. The lysis of Microcystis aeruginosa in AlCl3 sludge was more serious than that in PAFC sludge, for the same storage time. Although the cell viability in FeCl3 sludge was low (similar to AlCl3 sludge), the Microcystis aeruginosa cells remained basically intact after 10 d storage (similar to PAFC sludge). The maintenance of cellular integrity in FeCl3 sludge might be due to the large floc size and high density, which had a protective effect for Microcystis aeruginosa.


RSC Advances | 2016

Significantly enhanced dewatering performance of drinking water sludge from a coagulation process using a novel chitosan–aluminum chloride composite coagulant in the treatment of cyanobacteria-laden source water

Chunxia Ma; Haiyan Pei; Wenrong Hu; Juan Cheng; Hangzhou Xu; Yan Jin

The enhanced dewatering performance and the fate of cyanobacterial cells in the filtration of cyanobacteria-laden sludge, generated by a coagulation process using a novel composite chitosan–aluminum chloride (CTSAC) coagulant, were systemically studied. Two other cyanobacteria-laden sludge, aluminum chloride (AC) sludge and chitosan (CTS) sludge, were also studied to compare dewater performance with CTSAC sludge. Results showed that the dewatering process did not cause cell lysis and microcystins (MCs) release. The level of MCs and extracellular organic matter (EOM) in the filtrate were decreased by adsorption and sieving onto the cake layer formed on the membrane, but dewatering at high vacuum pressure reduced the rejection efficiency. The sludge from the coagulation process using the CTSAC composite displayed better sludge dewaterability and obtained a better quality of filtrate (fewer MCs and EOM) than those from AC and CTS coagulation processes independently. A three-dimensional excitation–emission matrix (EEM) fluorescence measurement indicated that protein-like substances in soluble extracellular polymeric substances (EPS) played a negative role on cyanobacteria-laden sludge dewatering. In addition, CTSAC sludge showed a more compact structure and larger floc sizes than AC sludge and CTS sludge for a strong improvement in the charge neutralization and bridge ability of AC by combining CTS in the composite coagulant. It was further observed that floc size played a more significant role on sludge dewaterability than the degree of compactness. Overall, the preferable dewater performance of CTSAC sludge demonstrated the CTSAC composite coagulant has great potential for the treatment of cyanobacteria-laden source water.


AIP Advances | 2015

Degradation mechanism of hydrogen-terminated porous silicon in the presence and in the absence of light

Hangzhou Xu; Haiyan Pei; Hongdi Xiao; Wenrong Hu

Si is well-known semiconductor that has a fundamental bandgap energy of 1.12 eV. Its photogenerated electrons in the conduction band can react with the ubiquitous oxygen molecules to yield ⋅O2− radicals, but the photogenerated holes in the valance band can’t interact with OH− to produce ⋅OH radicals. In this paper, we study the degradation of methyl orange (MO) by hydrogen-terminated porous Si (H-PSi) in the presence and in the absence of light. The absorption spectra of the degraded MO solutions indicated that the H-PSi had superior degradation ability. In the dark, the reduction of dye occurs simply by hydrogen transfer. Under room light, however, some of the dye molecules can be reduced by hydrogen transfer first and then decomposed in the conduction and valance bands. This result should be ascribed to its wide band gap energies centered at 1.79-1.94 eV.


Science of The Total Environment | 2017

The enhanced reduction of C- and N-DBP formation in treatment of source water containing Microcystis aeruginosa using a novel CTSAC composite coagulant

Chunxia Ma; Haiyan Pei; Wenrong Hu; Yuting Wang; Hangzhou Xu; Yan Jin

This study investigated the effect of a chitosan-aluminium chloride (CTSAC) composite coagulation process on reducing the formation of algal organic matters (AOM) related carbonaceous disinfection by-products (C-DBPs) and nitrogenous disinfection by-products (N-DBPs), by removing or adsorbing their precursors. Compared with aluminium chloride (AC) and chitosan (CTS) alone, CTSAC significantly enhanced the removal of dissolved organic matter (DOC), polysaccharide, protein and humic acids, attaining removals of 64.95%, 80.78%, 70.85% and 44.50%, respectively. Notably, the three-dimensional excitation and emission matrix (3D-EEM) combined with molecular weight (MW) fractionation analysis revealed that CTSAC was not only effective for removing high-MW AOM, but also for the low-MW fractions that are important in forming DBPs. In addition, the CTSAC coagulation was proven to enhance the removal of aromatic polypeptide/amino acid-like materials and aliphatic amines, which have high N-nitrosodimethylamine formation potential. Efficient AOM removal by the CTSAC coagulation resulted in significant reduction of both AOM-related C-DBPs (63.54%) and N-DBPs (71%), while AC coagulation did not substantially reduce the formation of tribromomethane, 1,1,1-trichloropropanone or N-nitrosodimethylamine, and CTS coagulation alone did not achieve any obvious reduction in trichloronitromethane. Fourier transform infrared (FT-IR) spectroscopy analysis confirmed the interaction of CTS and AC in the CTSAC composite coagulation, which contributed to the improved AOM removal performance of CTSAC, and, in this case, reduced the formation of C- and N-DBPs.


RSC Advances | 2016

Effect of chitosan quaternary ammonium salt on the growth and microcystins release of Microcystis aeruginosa

Yaowen Zhu; Haiyan Pei; Wenrong Hu; Yan Jin; Hangzhou Xu; Ying Ren; Di Xue

Developing effective methods to control Microcystis aeruginosa (M. aeruginosa) bloom is significant for repelling the adverse impact from hepatotoxic microcystins (MCs). Chitosan quaternary ammonium salt (HTCC), a water-soluble derivative of chitosan, shows excellent antioxidant and antibacterial properties. The present study was the first to research the application potential of HTCC in M. aeruginosa control. Five experimental groups with different doses of HTCC (0, 0.6 mg L−1, 1.2 mg L−1, 2.4 mg L−1, and 4.8 mg L−1) were built to explore the effects of HTCC on the growth and physiological changes of M. aeruginosa and the release of intracellular matter. The results indicated that the growth of M. aeruginosa was effectively inhibited by HTCC, and the inhibition efficiency was dependent on dosage within 7 days (d). Especially for the treatment with 4.8 mg L−1 HTCC, the inhibitory rate remained above 93.6% after 7 d exposure. However, the integrity of M. aeruginosa cells treated with 2.4 and 4.8 mg L−1 HTCC may be damaged and partial MCs were released. Furthermore, the release of MCs in the 1.2 mg L−1 HTCC treated groups was significantly lower than that of the control sample. To balance the inhibition efficiency of M. aeruginosa and the release of MCs, 1.2 mg L−1 was chosen as the appropriate dose for inhibiting the growth of M. aeruginosa and reducing the release of MCs. HTCC could damage the antioxidant defense system of M. aeruginosa and exhibit the inhibitive property. The results demonstrated HTCC can be used as an effective and safe inhibitor to control algal blooms.


Environmental Science & Technology | 2017

16S rRNA Gene Amplicon Sequencing Reveals Significant Changes in Microbial Compositions during Cyanobacteria-Laden Drinking Water Sludge Storage

Haiyan Pei; Hangzhou Xu; Jingjing Wang; Yan Jin; Hongdi Xiao; Chunxia Ma; Jiongming Sun; Hongmin Li

This is the first study to systematically investigate the microbial community structure in cyanobacteria-laden drinking water sludge generated by different types of coagulants (including AlCl3, FeCl3, and polymeric aluminum ferric chloride (PAFC)) using Illumina 16S rRNA gene MiSeq sequencing. Results show that Cyanobacteria, Proteobacteria, Firmicutes, Bacteroidetes, Verrucomicrobia, and Planctomycetes were the most dominant phyla in sludge, and because of the toxicity of high Al and Fe level in AlCl3 and FeCl3 sludges, respectively, the PAFC sludge exhibited greater microbial richness than that in AlCl3 and FeCl3 sludges. Due to lack of light and oxygen in sludge, relative abundance of the dominant genera Microcystis, Rhodobacter, Phenylobacterium, and Hydrogenophaga clearly decreased, especially after 4 days storage, and the amounts of extracellular microcystin and organic matter rose. As a result, the relative abundance of microcystin and organic degradation bacteria increased significantly, including pathogens such as Bacillus cereus, in particular after 4 days storage. Hence, sludge should be disposed of within 4 days to prevent massive growth of pathogens. In addition, because the increase of extracellular microcystins, organic matter, and pathogens in AlCl3 sludge was higher than that in FeCl3 and PAFC sludges, FeCl3 and PAFC may be ideal coagulants in drinking water treatment plants.


RSC Advances | 2016

The lysis and regrowth of toxic cyanobacteria during storage of achitosan–aluminium chloride composite coagulated sludge: implications for drinking water sludge treatment

Chunxia Ma; Haiyan Pei; Wenrong Hu; Hangzhou Xu; Yan Jin

Coagulation is a key unit operation for cyanobacterial cell removal; however, the potential danger of cyanobacterial cells transferred into sludge is not well understood. In this study, the fate of Microcystis aeruginosa (M. aeruginosa) and secondary metabolites in chitosan–aluminium chloride (CTSAC) coagulated cyanobacteria-laden sludge were investigated during the sludge storage period. The extracellular microcystins (MCs) can be adsorbed onto the CTSAC flocs for six days with a reduced biodegradation rate. Less M. aeruginosa cell lysis was observed in the coagulated system than in the natural cell system, due to the protection of M. aeruginosa by the CTSAC. Furthermore, the residual Al content decreased in the cyanobacteria-laden sludge supernatant. The amount of extracellular organic matter (EOM) stayed low in the coagulated system for four days. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis showed that coexisting bacteria reduced in the sludge during the initial four days storage time. Interestingly, the CTSAC degradation favored the growth of the M. aeruginosa cells. This study will be helpful for better understanding and managing secondary metabolite pollution problems related to coagulation-generated cyanobacteria-laden sludge during the sludge supernatant recycling process. The use of CTSAC composite coagulant is of practical value in reducing secondary pollution during cyanobacteria-laden sludge storage.


Journal of Photochemistry and Photobiology B-biology | 2016

Inactivation of Microcystis aeruginosa by hydrogen-terminated porous Si wafer: Performance and mechanisms

Hangzhou Xu; Haiyan Pei; Hongdi Xiao; Xiuqing Li; Chunxia Ma; Wenrong Hu

We proposed a method to inactivate Microcystis aeruginosa by using hydrogen-terminated porous Si (H-PSi) wafer. The influences of oxidation time on the removal of M. aeruginosa were investigated. Samples oxidized by H-PSi wafer were subsequently grown under illuminated culture conditions. The results demonstrated that the optimal oxidation time was about 1h, which could control the growth of M. aeruginosa about 65%, after 3days culture. Simultaneously, extracellular microcystins was decreased from 14.65 to 7.06μgL(-1) and remain relative integrity of M. aeruginosa cells which could avoid secretion of large amounts of organic material. Multiple analysis techniques including fluorescence excitation-emission matrix (EEM) and fluorescence microscope were used to reveal the inhibition mechanisms of M. aeruginosa. Meanwhile, analyses of reactive oxygen level, malondialdehyde content, and superoxide dismutase activity indicated that the damage and inactivate of M. aeruginosa cells are mainly due to accumulation of lipid peroxidation and inhibition of normal physiological metabolism by free radicals produced by H-PSi wafer under visible light irradiation. In conclusion, these results suggest that H-PSi wafer may be useful in controlling growth and survival of M. aeruginosa in many large lakes and reservoirs, thus mitigating many of the economic, esthetic ecological impacts of the invasive alga.

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