Effect of ozone on the formation and breakup of flocs in raw waters with high algae content


Yukselen M. A. , O'Halloran K., Gregory J.

JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A-TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING, cilt.41, sa.6, ss.1173-1182, 2006 (SCI İndekslerine Giren Dergi) identifier identifier identifier

  • Cilt numarası: 41 Konu: 6
  • Basım Tarihi: 2006
  • Doi Numarası: 10.1080/10934520600623067
  • Dergi Adı: JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A-TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING
  • Sayfa Sayıları: ss.1173-1182

Özet

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.