The rate at which it flows through the tank relative to the tank volume can be expressed in
terms of its detention time. Following a discussion of detention time we go on to look at the
physical characteristics of settling. This involves some calculations and you may find you
have to spend a little more time on them if your maths is a bit rusty. Try and work through the
equations but if you do get stuck don't worry, you will still be able to follow the main points.