Abstract
In this study, low-cost and non-polluting quartz sand was respectively mixed with AlCl3, FeCl3 and PAFC to synergistically remove Microcystis aeruginosa. Results showed that quartz sand could markedly increase the algae removal efficiency and decrease the coagulant doses. The increase of removal efficiency with AlCl3 and FeCl3 was only due to the enhancement of floc density by the quartz sand. However, the removal efficiency with PAFC was increased not only by the enhanced floc density, but also by the enlarged floc size. Flocs from 50 mg/L sand addition were larger than that with other sand doses, which was on account of the appropriate enhancement of collision efficiency at this dose. After coagulation, the extracellular organic matter (EOM) and microcystins (MCs) in system with quartz sand was remarkably reduced. That’s because quartz sand can enhance the coagulation so as to improve capping the EOM and MCs in flocs during coagulation process. Owing to 200 mg/L quartz sand could damage the cell’s membrane during coagulation proces, algal cells in the system lysed two days earlier than with 50 mg/L sand during flocs storage. In addition, cells with PAFC incurred relatively moderate cellular oxidative damage and could remain intact for longer time.
Highlights
IntroductionThe presence of harmful algal blooms (HABs) in water has represented a big challenge to drinking water plants
Over the past years, the presence of harmful algal blooms (HABs) in water has represented a big challenge to drinking water plants
One of the reasons that quartz sand was able to improve the M. aeruginosa removal efficiency might be that mixing flocs with sand would enhance their sedimentation properties
Summary
The presence of harmful algal blooms (HABs) in water has represented a big challenge to drinking water plants. Compared to soils and clays, sands are more commercially viable and completely harmless to water quality Ballast particles, such as clay, soil and sand, serve as seed grains when coagulation proceeds, while accelerating the sedimentation through increasing floc density[13]. The ballast should not accelerate algal cell lysis and algal toxin release during floc storage, which would degrade the quality of the water obtained upon dewatering the flocs (i.e. the ‘dewatering water’). Those researchers mainly combined organic coagulants (especially chitosan) with ballast to removal harmful algae. This study used low-cost and non-polluting quartz sand ( used in filter beds in drinking water plants) combined with AlCl3, FeCl3 or PAFC to remove M. aeruginosa
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