Urban rivers or water bodies play an important role in improving the ecological environment. However, many of them are turbid and uncomfortable. In this study, five species of microalgae were isolated from different natural water and used to find their growth potential, flocculation ability, turbidity and nutrient removal ability and the flocculation mechanisms were investigated. The results showed that, three microalgae species, namely, Ankistrodesmus sp. WZ3A4, Coelastrella tenuitheca W6D5, Chlorella sorokiniana W6A3 can efficiently reduce the turbidity in natural water. Optical microscope and SEM observations revealed that they can attach the suspended particles to form flocs and display high turbidity-removal efficiencies (TRE) of 74.7 %, 82.6 %, 93.8 % respectively in natural turbid water. Chlorella sorokiniana W6A3 can even reduce the turbidity from 60.3 NTU to 3.73 NTU. Through EPS component analysis, TRE changes and surface characteristics before and after EPS extraction, Fourier transform infrared (FTIR) spectrum analysis, we found that the high turbidity-removal efficiency of these microalgae species was not closely related to charge neutralization, but greatly associated with the tightly bound EPS and the high relative hydrophobicity. Hydrophobic interaction and the adhesion of extracellular macromolecular polysaccharides have important effects on the flocculation of microalgae in natural turbid water. FTIR showed that microalgae with higher turbidity-removal efficiencies all had stronger stretching vibration near 1135 cm −1 . This study demonstrates that light-driven self-flocculating microalgae can clarify natural turbid water while converting atmospheric carbon dioxide into living biomass through light energy and proposes a novel and carbon-negative technology for restoring urban turbid water environments.
A novel cationic flocculant of konjac glucomannan-graft-poly-(2-methacryloyloxyethyl)trimethyl ammonium chloride (KGM-g-PDMC), was successfully synthesized by using acidic ammonium cerium (IV) nitrate (CAN) as initiator in homogeneous aqueous solution. The graft copolymer was characterized using Fourier-transform infrared (FT-IR) spectroscopy, 1 H nuclear magnetic resonance ( 1 H NMR), thermogravimetric analysis (TGA) and elemental analysis. The influences of degree of substitution (DS) of KGM, concentration of NaCl and pH value on turbidity removal rate of the cationic flocculant were investigated. The results demonstrated that the flocculant exhibited excellent flocculating ability in the presence of salt and a wide range of pH (1 < pH < 9). With DS of 0.2, the turbidity removal rate of flocculant to 0.1% kaolin suspension could reach more than 90% at pH 7.0. The flocculation mechanisms were investigated by screening effect and means of zeta potential. Holding the positive charge, the KGM-g-PDMC could efficiently remove the negatively charged contaminants such as kaolin suspension.
Ruditapes philippinarum produces turbidity during hydrolysis, which may seriously hinder its further processing and utilization as a flavoring agent. In this study, the low-temperature crystallization properties of the oil components in the mixing system were combined with freezing flocculation to promote the aggregation, growth, and settling of the oil-peptide mixtures by ice crystal extrusion, which effectively solved the problems of secondary contamination and high cost associated with the traditional flocculation methods, while retaining the flavor of the enzymatic hydrolysate. The freezing process increased the contents of fresh, sweet, essential and total free amino acids in the supernatant by 1.94 %, 1.69 %, 1.45 % and 0.58 %, respectively, and these flavor amino acids optimized the flavor profile of the enzymatic digest. Freezing flocculation is a clean and sustainable flocculation technology that supports the sustainable development of the food industry and is in line with the trend of green production and environmental protection.
危险品化学品经营许可证（带存储）