Effect of ozone on the formation and breakup of flocs in raw waters with high algae content.
J ENVIRON SCI HEAL A
1173 - 1182.
The effect of ozone on the formation, breakup and re-formation of flocs generated using ferric sulphate has been investigated using conventional jar test procedure and by continuous optical monitoring using raw water. Using a range of different dosage of coagulant, the breakage of flocs was followed at a high stirring speed, corresponding to average shear rate (G) of about 518 s(-1). Most of the breakage occurred within a few seconds of increasing the shear rate. After breakage the stirring rate was reduced to the original value of 50 rpm (G approximate to 23 s(-1)) to allow the flocs to re-grow. It was found that only limited re-growth of flocs occurred indicating irreversibility of the floc breakup process. For preozonated samples, the re-growth of flocs occurred to a much greater extent with lower residual turbidity. The findings show that the use of preozonation (1.25 and 1.50 mg/L) provides beneficial results to both improve turbidity removal and reduce coagulant requirement. Furthermore, better re-formation of flocs is achievable.
|Title:||Effect of ozone on the formation and breakup of flocs in raw waters with high algae content|
|Keywords:||ferric sulphate, floc strength, floc breakage, coagulation, flocculation, ozone, DISSOLVED AIR FLOTATION, PARTICLE-SIZE, FLOCCULATION, OZONATION, FILTRATION|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Civil, Environmental and Geomatic Engineering|
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