Comparison of floc properties of coagulation systems: Effect of particle concentration, scale and mode of flocculation. Issue 5 (October 2020)

• Record Type: Journal Article
• Authors: Saxena, Kanika; Brighu, Urmila
• Is Part Of: Journal of environmental chemical engineering. Volume 8:Issue 5(2020)
• Publication Date: 2020-10
• Subjects: APHA American Public Health Association -- CC Conventional Clariflocculator -- CCD Charged coupled device -- DB Fractal dimension assessed using the Box counting method -- DBPs Disinfection By-products -- DOC Dissolved organic carbon -- G Velocity gradient -- HA Humic acid -- NOM Natural organic matter -- NTU Nephelometric turbidity unit -- PACl Poly aluminium chloride -- RPM Round per minute -- SBC Sludge blanket clarifier -- TOC Total organic carbon; Floc size -- Fractal dimension -- Enhanced coagulation -- Sludge blanket clarifier -- Pilot-scale coagulation; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2020.104311
• Languages: English
• ISSNs: 2213-2929

Abstract

Graphical abstract: Highlights: Floc properties depend on mode and scale of flocculation. Floc size increased with increased inorganic turbidity. Floc sizes were lesser in impeller mode than the hydraulic mode of flocculation. Size of residual particles did not depend on the scale and mode of flocculation. Floc stability may depend on the association of organics with inorganic turbidity. Abstract: This study is aimed to ascertain the influence of varying quantum of organic and inorganic colloids on parameters like floc size, fractal dimension and residual particle size, under alkaline conditions for water treatment by coagulation. Synthetic sample waters were prepared by using humic acid and kaolin for simulating organic matter and inorganic turbidity respectively. PACl (Poly aluminium chloride) was used as a coagulant. Image analysis for floc size measurement and box-counting method for fractal dimension measurement has been used. A batch jar test reactor and two continuous flow pilot-scale reactors: 1. Conventional clariflocculator (CC) and 2. Sludge blanket clarifier (SBC) were studied to evaluate the effect of scale-up on floc properties. The pilot systems differed in the mode of flocculation, as CC used a mechanical impeller and SBC used hydraulic mode for flocculation. For CC, the trendlines indicated a decrease in the size of flocs with increasing organic concentration. The order of floc size was: SBC > jar test > CC. The average fractal dimension of flocs in jar test was 1.28 which was lesser than that in CC (1.51) indicating more filament-like structure of flocs in jar test. The floc sizes and fractal dimensions depended on the scale and mode of flocculation. The size of residual particles in the treated water was quite similar irrespective of the scale and mode of flocculation. However, the trends were opposite with increasing input TOC. For jar test, the residual particle sizes decreased and for pilot-scale, it increased with increasing input TOC.