A sinuous channel has 15 round-the-end cross-walls. Water is passed along with a velocity of 0.2 m/s between the cross-walls and 0.5 m/s round the ends. The flow is 0.3 m ³/s and the nominal retention time is 25 min. For a temperature of 10 C, estimate the additional loss of head, the power dissipated, and the G and GT values (Fig. A1.1).

Figure A1.1: Sinuous channel for flocculation

Using equation (5.2):

and

Using equation (5.1):

Thus

A flow of 50 000 m ³/day is to be dosed with a coagulant. Destabilization will be by double layer compression. To ensure proper mixing a G of 1500 s ^{? 1} is required. Assuming that the flow over the weir discharges into a chamber with a volume of 2 m ³, what height of weir is required?

Therefore

retention time in mixing chamber = 2 m ³/(0.58 m ³/s) = 3.4 s.

Apply equation (5.3):

Thus

Thus