Publications by authors named "Minhui Guo"

4 Publications

  • Page 1 of 1

New insights into interaction of proteins in extracellular polymeric substances of activated sludge with ciprofloxacin using quartz crystal microbalance with dissipation.

Chemosphere 2021 Jan 25;263:128044. Epub 2020 Aug 25.

Department of Civil and Environmental Engineering, Ningbo University, Ningbo, 315211, China.

Proteins in extracellular polymeric substances play a vital role in adsorbing organic contaminants in biological wastewater treatment processes, but there is still lack of a fast and effective approach to monitor their interaction. Quartz crystal microbalance with dissipation (QCM-D) was used to investigate the binding and viscoelastic properties of ciprofloxacin (CIP) on extracellular proteins from activated sludge by a two-step sequential deposition method. A saturated viscoelastic monolayer of proteins was formed on the crystal by injecting 500 mg L extracellular proteins. Binding of CIP with the extracellular proteins film followed the pseudo-first-order kinetic equation and Langmuir model, with the maximum binding capacity of 172.4 mg g. The binding mass, energy dissipation, and reaction rate constant increased with increasing CIP concentration. A strong binding was obtained at pH 5, suggesting electrostatic interactions as the dominating binding mechanism. Cations inhibited CIP binding with extracellular proteins, probably due to cations competition. Two binding periods were distinguished according to the viscoelastic properties of CIP layer: viscous binding in the initial period and elastic towards binding saturation. Results highlighted QCM-D as an effective and real-time technique to evaluate the role of extracellular proteins in contaminants removal.
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http://dx.doi.org/10.1016/j.chemosphere.2020.128044DOI Listing
January 2021

Multiple roles of Ca in the interaction of ciprofloxacin with activated sludge: Spectroscopic investigations of extracellular polymeric substances.

Sci Total Environ 2021 Jan 7;751:142246. Epub 2020 Sep 7.

Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China. Electronic address:

Calcium ion is an important cation influencing the binding of recalcitrant organic contaminants with activated sludge during wastewater treatment process, but there is still unknown about its role in amphoteric fluoroquinolones binding. Binding experiments show that Ca markedly inhibited binding of ciprofloxacin (CIP) onto sludge, causing 7-203 times of CIP release. Multi-spectroscopic examinations indicate that tryptophan-like and tyrosine-like proteins in extracellular polymeric substances (EPS) were dominant components for CIP binding by static quenching and forming CIP-proteins complexes. Addition of Ca into EPS and CIP binding systems induced increase of association constants (from 0.024-0.064 to 0.027-0.084 L/μmol) and binding constants (from 0.002-0.039 to 0.012-0.107) and decrease of binding sites number (from 0.893-2.007 to 0.721-1.386). Functional groups of EPS and secondary structure of proteins were remarkably changed upon reactions with CIP and Ca. Calcium ion interacted with EPS and CIP binding system in two distinct ways: Ca shielded CO in amide I in EPS for CIP binding, whereas strengthened binding between CIP and functional groups including CO in carboxyl groups in extra-microcolony polymers and OH in extra-cellular polymers by forming ternary complexes. Cation competition for CO in amide I is responsible for Ca induced CIP release from the sludge. Results suggest the highly potential release of CIP from high saline wastewater and cation-conditioned sludge which needs further monitoring and evaluation.
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http://dx.doi.org/10.1016/j.scitotenv.2020.142246DOI Listing
January 2021

The role of temperature and CaCl2 in activated sludge dewatering under hydrothermal treatment.

Water Res 2014 Mar 28;50:10-7. Epub 2013 Nov 28.

Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China. Electronic address:

Dewatering is important for activated sludge disposal. The dewaterability of activated sludge was first deteriorated and then ameliorated when the temperature was raised from 100 to 200 °C with a threshold temperature of 130 °C under hydrothermal treatment. Calcium chloride assisted hydrothermal treatment to improve the dewaterability of activated sludge, and eliminated the threshold temperature at as less as 20 mg/g dry solid (DS). An increase in temperature and dosage of CaCl2 till 60 mg/g DS allowed a continuous improvement of dewaterability. It is found that the charge neutralization resulted from biopolymers solubilization dominated the dewaterability evolution below 160 °C, while the decomposition of water-binding components played a more important role at higher temperatures. The variation of molecular weight of soluble protein and polysaccharides implies that CaCl2 interacted with the component of sludge and altered the constituent during the hydrothermal treatment. The integration of soluble biopolymers into the floc matrix by CaCl2 contributed to the compacted floc structure and thus improved the dewaterability. This work presents an insight into the floc variation in both the composition and structure associated with the dewaterability and offers a new understanding to the role of temperature and CaCl2 in hydrothermal treatment on activated sludge dewatering.
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http://dx.doi.org/10.1016/j.watres.2013.11.034DOI Listing
March 2014

Improvement of activated sludge dewaterability by mild thermal treatment in CaCl2 solution.

Water Res 2012 Feb 13;46(2):425-32. Epub 2011 Nov 13.

Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China.

Activated sludge dewatering is of great importance in sludge treatment and disposal. To enhance the dewaterability, a novel method was performed by treating the sludge under mild temperature (50-90 °C) in CaCl(2) solution (3.7-1110.0 mg/g dry sludge). The capillary suction time, zeta potential, Fourier-transformed infrared spectra, concentration of soluble protein and carbohydrates were employed to characterize the dewaterability and influencing mechanism. The sludge dewaterability was deteriorated with single thermal treatment, but significantly promoted in CaCl(2) solution and advanced further together with thermal treatment. An increasing CaCl(2) dosage reduced the surface charge remarkably, and a higher temperature could strengthen this impact. The spectra indicate that Ca(2+) could interact with the protein, phenols and O-H functional group in the flocs. The thermal treatment could cause the solubilization of protein and carbohydrates, providing more binding sites for Ca(2+) to establish a strong bridging among the flocs. As CaCl(2) dosage elevated, the soluble carbohydrates showed a reduction trend, while the soluble protein lowered firstly and then bounced back except that remained unchanged at room temperature. A bridging equilibrium is presumed to exist between Ca(2+) and the soluble protein. And the bridging between Ca(2+) and the soluble carbohydrates plays a more important role in the dewatering. The sludge dewaterability was successfully and economically improved by thermal treatment in CaCl(2) solution.
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http://dx.doi.org/10.1016/j.watres.2011.11.014DOI Listing
February 2012