Experiences with the Application of Starch Derivates in the Sludge Blanket Treatment

Sludge blanket clarifiers are nowadays quite commonly used in water treatment practice. In hydraulic aspect the sludge blanket represents essentially a fluidized layer of floc particles in water, in chemical-technological point of view it represents the orthokinetic stage of coagulation. In this work the authors examine the influence of hydraulic and technological factors on the sludge blanket operation. They examine also the possibility of improving the performance by the addition of organic flocculants, especially of starch derivates. They verify the results obtained from laboratory pilot-plant runs on a sludge blanket unit with the capacity of 100 I/sec. They conclude:

• a) The effects of local head losses and sludge blanket weight on the orthokinetic phase of coagulation are the same;
• b) the addition of organic flocculants will increase only slightly the mass density of the sludge blanket as well as that of a single floc;
• c) the separation efficiency of the sludge blanket will be improved with the increase of the Camp number;
• d) the starch derivates at a slightly higher dose than the commercial flocculants have the same effect as synthetic organic flocculants; however, the operation costs seem to be lower.