WATER ENVIRONMENT RESEARCH
·
2020
·Vol. 93
·期 5
·693-702
·
IF 1.369
Yonglei Wang,Ya'nan Li,Liping Tian,Ling Ju,Yulei Liu
Microplastics (MPs) are widely distributed in freshwater and have the following characteristics: small size, strong hydrophobicity, difficult degradation, and easy adsorption of toxic substances. These characteristics pose a potential threat to the environment and human health. In this paper, three common MPs in freshwater were removed by conventional dissolved air flotation (DAF) and positive modification DAF (Posi-DAF). The results showed that the optimal removal efficiency of MPs by conventional DAF was 32%–38% at 0.4–0.5 MPa. This indicated that the adhesion between microbubbles (MBs) and MPs was not ideal when the hydrophilic/hydrophobic interaction was the dominant mechanism. However, the removal efficiency of MPs was increased by 13.6%–33.7% compared with that of conventional DAF after two surface modifiers were used on MBs. This result indicated that in addition to the hydrophilic/hydrophobic interaction, both charge attraction and sweeping had positive effects. Practitioner points The removal efficiency and mechanism of MPs by posi-DAF were investigated. The characteristics, particle number, and adhesion of microplastics were measured. Conventional DAF was dominated by hydrophilic/hydrophobic interactions. CTAB Posi-DAF was dominated by charge attraction. PDADMAC Posi-DAF was dominated by charge attraction and sweeping.
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Journal of Water Process Engineering
·
2022
·
IF 7.34
Xiaohong Wang,Yonglei Wang,Liping Tian,Ling Ju,Ruibao Jia,Wuchang Song,Haiyang Yu,Jingjing Li
The eutrophication of reservoir water leads to the proliferation of algae, the DAF process can overcome the lack of algae removal capacity in conventional treatment processes, and its pollution removal efficiency is affected by the equipment performance. Among DAF equipment, multiphase flow pumps have attracted attention because of their simple configuration and low failure rate. This paper studied the equipment performance and pollution removal efficiency of a multiphase flow pump for DAF. The results showed that the dissolution efficiency of the equipment was approximately 55% and the average particle size of bubbles was less than 26 μm. When the pressure was greater than 0.36 MPa, the bubble stability time exceeded 4 min. The optimal working conditions were achieved at a dissolved gas pressure of 0.4 MPa. The maximum removal rates of turbidity , chlorophyll a , TOC, UV 254 and COD Mn by the DAF process were 56.49%, 50.23%, 23.73%, 28.75% and 23.98%, respectively. The trend in pollution removal efficiency was consistent with that of equipment performance parameters. The surface of the microbubbles was hydrophobic and could more easily adsorb high-molecular-weight organic substances with strong hydrophobicity and algae with strongly hydrophobic colloidal layers inside. In addition, regarding the THMFP, the experimental results showed that the removal rates of the precursors CHCl 3 , CHBrCl 2 and CHBr 2 Cl after DAF were 28.93%, 23.26% and 21.53%, respectively. Surface hydrophobicity is one of the main mechanisms by which microbubbles adhere to pollutants.
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
高影响因子
Frontiers of Environmental Science & Engineering
·
2017
·Vol. 11
·期 6
·1-10
·
IF 1.716
Shi Yulong,Yang Jiaxuan,Ma Jun,Luo Congwei
A novel, functionalized bubble surface can be obtained in dissolved air flotation (DAF) by dosing chemicals in the saturator. In this study, different cationic chemicals were used as bubble surface modifiers, and their effects on natural organic matter (NOM) removal from river water were investigated. NOM in the samples was fractionated based on molecular weight and hydrophobicity. The disinfection byproduct formation potentials of each fraction and their removal efficiencies were also evaluated. The results showed that chitosan was the most promising bubble modifier compared with a surfactant and a synthetic polymer. Tiny bubbles in the DAF pump system facilitated the adsorption of chitosan onto microbubble surfaces. The hydrophobic NOM fraction was preferentially removed by chitosan-modified bubbles. Decreasing the recycle water pH from 7.0 to 5.5 improved the removal of hydrophilic NOM with low molecular weight. Likewise, hydrophilic organic compounds gave high dihaloacetic acid yields in raw water. An enhanced reduction of haloacetic acid precursors was obtained with recycle water at pH values of 5.5 and 4.0. The experimental results indicate that NOM fractions may interact with bubbles through different mechanisms. Positive bubble modification provides an alternative approach for DAF to enhance NOM removal.
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
高影响因子
Journal of Water Process Engineering
·
2021
·
IF 5.485
Yonglei Wang,Wentao Sun,Luming Ding,Wei Liu,Liping Tian,Yinhe Zhao,Mengyu Zhang,Xuelin Wang
Water from the Yellow River reservoir is treated by dissolved air flotation (DAF), but the flocs formed are loose and easily desorbed. To solve this problem, a new air flotation process, i.e., Posi-co-coagulation dissolved air flotation (Posi-CCDAF), was developed by combining DAF with microbubble surface modification technology. The feasibility of the Posi-CCDAF process was verified by using chitosan to modify the surfaces of the microbubbles. The optimal dosage ratio of chitosan/coagulant was 0.4, and the optimal pH of the reflux water was 6.00. The removal characteristics of organic pollutants under the optimal conditions were studied. The removal characteristics of natural organic matter (NOM) with different molecular weights before and after adding chitosan were compared, and the removal efficiency of disinfection byproduct precursors was evaluated. Microscopic analysis was used to observe the bubble floc adhesion process and flocs during the copolymerization process before and after the addition of chitosan. The results showed that chitosan promoted the removal of hydrophobic macromolecular organics and the trihalomethane formation potential (THMFP) by CCDAF. On the one hand, the surface of modified microbubbles in Posi-CCDAF was positively charged, which provided electrostatic force to enhance the adhesion of flocs during polymerization; on the other hand, the combination of chitosan and macromolecular organics in water formed a capture network, which made the bubble flocs larger and caused them to adhere tightly, improving the removal effect of air flotation.
研究领域:
环境科学
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水处理技术
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）