Location:Home > Engineering science > Materials Processing Engineering > Study on the Effect of Flocculant and Sludge on Regrowth after Breakage of Floc in Water
Details
Name

Study on the Effect of Flocculant and Sludge on Regrowth after Breakage of Floc in Water

Downloads: []
Author
Tutor: NanJun
School: Harbin Institute of Technology
Course: Municipal Engineering
Keywords: flocculant,floc breakage,average floc size,floc strength,fractaldimension
CLC: TU991.22
Type: Master's thesis
Year:  2012
Facebook Google+ Email Gmail Evernote LinkedIn Twitter Addthis

not access Image Error Other errors

Abstract:
Flocculation is one of the most important operational units in water treatment. People try to form big and compact floc to improve the effect of water treatment, in the process, floc breakage must occur, so the realizing of floc breakage is significant. Most researches show that only limited regrowth of floc occur after breakage, and adding coagulant during the breakage can improve the floc regrowth, but the kinds of coagulant used in breakage are limited and there are none research of organic polymer flocculant. In the flocculation, there may be more than one times breakage, so the breakage resistance and regrowth abilities of floc is worth to research. The regrowth of floc means the sludge activity, so the sludge added in breakage time can promote the floc regrowth. This method can improve the effect of flocculation in practice.The research was based on flocculation test. For each test, kaolin and humic acid suspension was used as testing water sample and polyaluminum chloride (PAC) was selected as the initial flocculant. PAC, polyacrylamide(PAM) or sludge of PAC was added in breakage to study floc breakage and regrowth by an in-situ recognition technique of floc morphology in water.For the once breakage process, when PAC was used in the breakage, the proportion of small size floc was reduced, and the bigger flocs occured, the higher the dosage of flocculant used, the bigger the average floc size and the lower residual turbidity; when PAM was used in the breakage, the proportion of small size floc was reduced yet, but when the dosage was high there was colloid protection phenomenon. For the twice breakage process, when PAC was used in the first breakage, the hydrolysate had promotion on the twice broken floc regrowth; when PAC was used in the second breakage, the recovery ability was bigger than it in the first breakage time. When PAM was used in the first breakage time, the floc strength of floc formed after first breakage was high, but after the second breakage the floc recovery ability was very low; When PAM was used in the second breakage time, the dosage had little influence on the effect of flocculant. Adding sludge in the breakage could promote the floc regrowth, reduce the time of average floc size reaching to steady state, and the higher the dosage of sludge, the lower the residual turbidity; the floc formed when adding sludge in the breakage55s had bigger fractal dimension and more compact structure than it adding sludge at the beginning of breakage.As to stirred vessel, using flocculant again in the high shear rate area near the agitator can promote the broken floc to regrow and improve the effect of water treatment. Backflowing the sludge to area near the agitator can increase the probability of floc collision so as to promote the broken floc to regrow; it can also reduce the time of average floc size reaching to steady state, so we can reduce hydraulic retention time and low the cost of stirred vessel.
Related Dissertations
Last updated
Sponsored Links
Home |About Us| Contact Us| Feedback| Privacy | copyright | Back to top