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Water Science & Technology Vol 50 No 12 pp 63–70 © IWA Publishing 2004 The duplicity of floc strengthP. Jarvis*, B. Jefferson** and S. Parsons****School of Water Sciences, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, United Kingdom (E-mail: p.jarvis@cranfield.ac.uk; b.jefferson@cranfield.ac.uk; s.a.parsons@cranfield.ac.uk) ABSTRACT The breakage of flocs is dependent upon the strength of the bonds holding the aggregate together. The present work describes the breakage and re-growth behaviour of three different types of floc, these were: 1) coagulant precipitate flocs, 2) turbidity flocs and 3) organic matter flocs. Floc aggregates were exposed to increased levels of shear on a conventional jar tester and the sizes of the flocs were observed dynamically using a laser diffraction instrument. The organic flocs showed most resistance to breakage across the whole range of shears under investigation. The dynamic procedure provided detailed information on particle size distributions (PSD). Large and small scale degradation events could be identified from analysis of the PSD data. All of the flocs under investigation showed little re-growth potential after breakage. The precipitate and organic flocs showed slightly better re-aggregation of the small floc sizes. PAY-PER-VIEW: Buy this article for £23.5 (IWA MEMBER PRICE: £17.62) - All prices include VAT |
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