Abstract:
A sludge blanket clarifer is a treatment unit combining flocation and upward flow sedimentation, which is more efficient compared to the conventional sedimentation tank. It has the abiltiy to treat the water at a faster rate, resulting in less space requirement. The performance of the blanket
appears to directly depend on the raw water quality, coagulant concentration, temperature and up
flow velocity. However, there are no direct relationships available to help the operators to adjust these
variables to obtain satisfactory performance of the clarifier. Hence it is ksential to identify a
characteristic that can be used as an indicator to monitor the sludge blanket. A study of literature
showed that a parameter called "sludge cohesion coefficient (SCC)" of sludge has been used in France
(Degremont, 1991) to characterize the sludge blanket. However, the procedure given was not clear,
and parameters to characterize performance of sludge blanket clarifiers in the tropical environments
could not be found in the literature studied. Therefore this research was conducted to study the
behaviour of a sludge blanket using the parameter SCC, which was done in two stages. During first
stage development of a standard test procedure and introduction of cohesion coefficient ranges which
be expected under tropical climatic condition were done. Under this stage several laboratory tests
conducted and a test procedure was finalized. In the second stage, using the developed test
can
were
procedure, SCC of synthetic raw water samples was measured to develop relations between the SCC
and other variables. Results showed that there is an optimum range of alum dose that produced the
sludge blanket with the highest SCC under controlled raw water conditions.
Citation:
Nithini, T.A.S., & Rathnayake, N. (2014). Water treatment using sludge blanket clarifiers. In M.T.P. Hettiarachchi (Ed.), Proceedings of the Civil Engineering Research Symposium 2014 (pp. 105-110). Department of Civil Engineering, University of Moratuwa.