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Evaluation of Dewatering Performance and Fractal Characteristics of Alum Sludge.

Sun Y, Fan W, Zheng H, Zhang Y, Li F, Chen W - PLoS ONE (2015)

Bottom Line: Floc-size measurements demonstrated that high flocculant dosage significantly improved floc size.Correlation analysis further revealed a strong correlation between fractal dimension and floc size after flocculation.A strong correlation also existed between floc size and zeta potential, and flocculants with a higher cationic degree had a larger correlation coefficient between floc size and zeta potential.

View Article: PubMed Central - PubMed

Affiliation: Key laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, China.

ABSTRACT
The dewatering performance and fractal characteristics of alum sludge from a drinking-water treatment plant were investigated in this study. Variations in residual turbidity of supernatant, dry solid content (DS), specific resistance to filtration (SRF), floc size, fractal dimension, and zeta potential were analyzed. Sludge dewatering efficiency was evaluated by measuring both DS and SRF. Results showed that the optimum sludge dewatering efficiency was achieved at 16 mg∙L(-1) flocculant dosage and pH 7. Under these conditions, the maximum DS was 54.6%, and the minimum SRF was 0.61 × 10(10) m∙kg(-1). Floc-size measurements demonstrated that high flocculant dosage significantly improved floc size. Correlation analysis further revealed a strong correlation between fractal dimension and floc size after flocculation. A strong correlation also existed between floc size and zeta potential, and flocculants with a higher cationic degree had a larger correlation coefficient between floc size and zeta potential. In the flocculation process, the main flocculation mechanisms involved adsorption bridging under an acidic condition, and a combination between charge neutralization and adsorption-bridging interaction under neutral and alkaline conditions.

No MeSH data available.


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Effect of pH on the residual turbidity of supernatant.
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pone.0130683.g003: Effect of pH on the residual turbidity of supernatant.

Mentions: Fig 3 shows the effect of pH on the residual turbidity of the supernatant after flocculation. The supernatant turbidity of CPAM1 decreased with increased pH. However, with increased pH, the supernatant turbidity of CPAM2 and CPAM3 decreased initially until pH 5, and then increased dramatically. The minimum residual turbidity of CPAM1 and CPAM2 supernatants were 16.1 and 11.2 NTU, respectively, obtained at pH 5. Meanwhile, the residual turbidity of CPAM1, CPAM2, and CPAM3 were also determined at pH 11, obtaining 143, 971, and 653 NTU, respectively, which were much larger than the values of residual turbidity obtained at other pH values. The high residual turbidity values obtained at pH 11 show that flocculation performance deteriorated significantly in strong alkaline conditions. During the flocculation tests, sludge flotation was observed at pH 1, and the supernatant was yellow. At pH 11, the supernatant, which is a mixture of many fine sludge particles, was muddy.


Evaluation of Dewatering Performance and Fractal Characteristics of Alum Sludge.

Sun Y, Fan W, Zheng H, Zhang Y, Li F, Chen W - PLoS ONE (2015)

Effect of pH on the residual turbidity of supernatant.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487249&req=5

pone.0130683.g003: Effect of pH on the residual turbidity of supernatant.
Mentions: Fig 3 shows the effect of pH on the residual turbidity of the supernatant after flocculation. The supernatant turbidity of CPAM1 decreased with increased pH. However, with increased pH, the supernatant turbidity of CPAM2 and CPAM3 decreased initially until pH 5, and then increased dramatically. The minimum residual turbidity of CPAM1 and CPAM2 supernatants were 16.1 and 11.2 NTU, respectively, obtained at pH 5. Meanwhile, the residual turbidity of CPAM1, CPAM2, and CPAM3 were also determined at pH 11, obtaining 143, 971, and 653 NTU, respectively, which were much larger than the values of residual turbidity obtained at other pH values. The high residual turbidity values obtained at pH 11 show that flocculation performance deteriorated significantly in strong alkaline conditions. During the flocculation tests, sludge flotation was observed at pH 1, and the supernatant was yellow. At pH 11, the supernatant, which is a mixture of many fine sludge particles, was muddy.

Bottom Line: Floc-size measurements demonstrated that high flocculant dosage significantly improved floc size.Correlation analysis further revealed a strong correlation between fractal dimension and floc size after flocculation.A strong correlation also existed between floc size and zeta potential, and flocculants with a higher cationic degree had a larger correlation coefficient between floc size and zeta potential.

View Article: PubMed Central - PubMed

Affiliation: Key laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, China.

ABSTRACT
The dewatering performance and fractal characteristics of alum sludge from a drinking-water treatment plant were investigated in this study. Variations in residual turbidity of supernatant, dry solid content (DS), specific resistance to filtration (SRF), floc size, fractal dimension, and zeta potential were analyzed. Sludge dewatering efficiency was evaluated by measuring both DS and SRF. Results showed that the optimum sludge dewatering efficiency was achieved at 16 mg∙L(-1) flocculant dosage and pH 7. Under these conditions, the maximum DS was 54.6%, and the minimum SRF was 0.61 × 10(10) m∙kg(-1). Floc-size measurements demonstrated that high flocculant dosage significantly improved floc size. Correlation analysis further revealed a strong correlation between fractal dimension and floc size after flocculation. A strong correlation also existed between floc size and zeta potential, and flocculants with a higher cationic degree had a larger correlation coefficient between floc size and zeta potential. In the flocculation process, the main flocculation mechanisms involved adsorption bridging under an acidic condition, and a combination between charge neutralization and adsorption-bridging interaction under neutral and alkaline conditions.

No MeSH data available.


Related in: MedlinePlus