E. Aiguier et al., METHODS FOR DETERMINING THE SETTLING VELOCITY PROFILES OF SOLIDS IN STORM SEWAGE, Water science and technology, 33(9), 1996, pp. 117-125
Citations number
6
Categorie Soggetti
Water Resources","Environmental Sciences","Engineering, Civil
Recently, research has shown that a settling process is an efficient t
reatment for the removal of suspended solids from storm sewage. In ord
er to design settling tanks, there is a need to determine the settling
velocity characteristics of these solids. Devices and test methods fo
r measuring Settling velocities of solids in storm sewage have been de
veloped by researchers. A literature review has revealed that the sett
ling velocity profiles obtained with some methods (Chebbo, 1992), (Mic
helbach and Wohrle, 1993) and (Tyack et al., 1993) are very different.
In order to explain why the results are different and to quantify the
influence of the experimental procedure on the settling velocity grad
ing curves, we have compared the selected methods when tested with the
same sample and we have studied the effects of the conservation of th
e sample before the test, of the concentration of solids in the device
and of the nature of the water on the settling velocity profiles. The
results of the comparative tests indicate that the settling velocitie
s are significantly lower with both the Cergrene and Aston methods tha
n with the UFT test procedure. Moreover, the study has shown that the
settling characteristics of solids change with time, that the use of s
ewage liquor rather than demineralised water or drinking water can cha
nge the results of the measurement and that the higher the concentrati
on of solids, the greater the velocity of settled particles. Copyright
(C) 1996 IAWQ. Published by Elsevier Science Ltd.