Treatment Plants for Phosphorus Removal from Wastewater
Figs 10.16 and 10.17 show that there is a big difference in the flocculation ability of
the different chemicals, that it is advantageous to divide the flocculation tank into
several chambers, and that in order to obtain a given degree of flocculation, a
minimum retention time is required, and that there is an optimum mean velocity
gradient, G.
Example 1 0.3
Phosphorus is precipitated by adding an aluminium sulphate product, 250 g/m 3 . The
aluminium content is 8 per cent on a weight basis. The wastewater, 180 m 3 /h, contains
Mean velocity gradient, G
120
Aluminium
100
80
FG = 10
60
40
30
40 50
Hydraulic
c:
retention time, 9
20
20 40 60 80 100 120 140 160
min
5 10
Mean velocity gradient, G
20
100
Aluminium+
80
polymer
60
40
50
40
Hydraulic
retention time, 9
20
20 40 60 80 100 120 140 160
min
Fig 10.17 Degree of flocculation as a function of mean velocity gradient, G, hydraulic retention
time, 9, and precipitant. Number of chambers, n = 2, /6/.
14 g P/m 3 .
1.
What is the molar ratio applied?
329