The sewer tank is a specific type of overflow tank. While sewer tanks
with a surplus flow at the beginning of the sewer are regarded as uncr
itical, in sewer tanks with a surplus flow at the end of the sewer, se
dimentation may be remobilised and transported into the receiving wate
rs. For this reason, in Germany, additional capacity over and above th
e minimum requirements is demanded for these sewers. In order to ensur
e the qualitative mode of action of sewer tanks with a surplus flow at
the end of the sewer, pilot-scale investigations into a model sewer,
with artificial combined water, as well as large-scale investigations
under real life conditions, were carried out. The findings of these in
vestigations illustrated that a sedimentation of solids takes place in
the majority of flow circumstances, including times of overflow. Thus
, even at times of high stormwater flow, the outflow to the receiving
waters contains only a low level of pollution. As well as storing the
stormwater, the sewer tank with a surplus flow at the end of the sewer
has the additional environmentally friendly effect of improving the q
uality of the outflow and reducing its pollution content. Copyright (C
) 1996 IAWQ. Published by Elsevier Science Ltd.