Low-cost methodology for the characterization of floc size in low turbidity and low alkalinity waters using image analysis

Abstract

Floc-particle size in drinking water treatment is an important parameter for designing and operating clarification and filtration units. However, advanced techniques for floc characterization are not affordable in drinking water utilities in developing countries because they are expensive and require qualified and training personnel. Therefore, the main objective of this research was to develop and test a nonintrusive low-cost methodology for floc size characterization using a regular HUAWEI P30 cell phone equipped with 40 megapixels camera, which is significantly less expensive than a sophisticated high-speed high-resolution camera used for floc characterization based on image analysis. This technique does not require sample processing, which keeps unaltered floc/particles aggregates for analysis. The methodology was calibrated using four different source waters with low turbidity (≤5.95±0.48 NTU) and relatively low alkalinity (≤52.4± 4.12 as CaCO3), which are typical from the Andina Region in Colombia. This methodology demonstrated to be useful for obtaining the mean floc size (based on average Feret diameter), floc area, floc perimeter and circularity of aggregates formed by the addition of alum [Al2(SO4)3*18H2O] after 15 minutes of flocculation in a regular jar tester. The methodology also proved to be valuable for measuring floc sizes in a range between 33 μm and 1,200 μm. HIGHLIGHTS Development of a low-cost methodology for flocs size characterization in developing countries.; Determination of floc physical characteristics, mean diameter, perimeter, area, and circularity.; Impact of raw water turbidity and coagulant dose on flocs size.; Calculation of the floc settling velocity in sedimentation units.;

Keywords

• coagulation
• flocculation
• flocs
• image analysis
• sedimentation