Application of low-mixing energy input for the coagulation process

Galvanic Corrosion of Lead by Iron (Oxyhydr)Oxides: Potential Impacts on Drinking Water Quality

“…For electrolyte preparation, orthophosphate was added as phosphoric acid (Fisher Scientific) from a 1.0 M stock solution. Humic acid stock was prepared by dissolving 500 mg sodium humate (Alfa Aesar, 38.4% carbon) 32 in 1 L of ultrapure water; the stock solution was then centrifuged at 3000 rpm for 10 m to remove undissolved particles. For size-exclusion chromatography separations, ammonium acetate was purchased from Sigma-Aldrich and tris (hydroxymethyl) aminomethane from Fisher Scientific.…”

Influence of the Mixing Energy Consumption Affecting Coagulation and Floc Aggregation

“…The iron to carbon ratio (i.e., >0.8 mg Fe/mg TOC) used as OCC in the present study resulted in a rapid growth of ferric flocs in the rapid mixing stage itself kept at a G of 175 s −1 , which was well within the optimal operating range (i.e., 110 s −1 < G < 450 s −1 ) of mixing energy input recommended for enhanced coagulation. 11 This corresponds to an energy usage of 27 kW-h/day for a 120 million liters/day representative treatment facility.…”

“…An overall decreasing trend of residual turbidity with time indicated the settling process had a dampening effect on the differences in floc characteristics due to coagulation mixing energy. In other words, there was no significant difference in the settling kinetics after 60 min, particularly in the recommended mixing energy range of 11−181 kW-h. 11 The compact flocs (essentially smaller size particles) resulting from a higher coagulation mixing energy were able to settle given enough time, except for the data shown at 0 and 1879 kW-h/day. As expected, when the coagulation mixing energy was at 0 kW-h/day (i.e., G = 0 s −1 ) and 1879 kW-h/day (i.e., G = 1450 s −1 ), the residual turbidity was fairly high (>2 NTU) even after a settling time of 90 min (at an overflow rate of 0.1 cm/min).…”

“…Coagulation and flocculation experiments were tested at two pH conditions, a slightly acidic pH of 4.80 and a near neutral pH of 6.85, following a procedure similar to that of Vadasarukkai et al In that study, which used the same source water from Kelly Lake, an iron dose of 0.33 mM and 0.66 mM was determined as optimal coagulant concentration (OCC) of ferric sulfate at pHs 4.80 and 6.85, respectively. At the OCC, the authors showed total organic carbon (TOC) concentration and residual turbidity decreased following settling in the treated water.…”

“…Experimental investigations have supported the theory that the coagulation process has a great potential for energy savings with regards to rapid mixing conditions, without sacrificing water quality standards. 10−12 For instance, Vadasarukkai et al 11 have proposed a low-mixing intensity range of 110 s −1 < G < 450 s −1 for a combined effective removal of turbidity and dissolved natural organic matter (DOM). Alternatively, a more sustainable system for coagulation mixing, such as pipe and open channel static mixers, are now available to water plants.…”