Environmental Engineering Reference
In-Depth Information
PAVEMENT LEVEL
WATER INTAKE
AT BACK OF UNIT
(CYLINDRICAL SCREEN
WITH ROTATING BRUSES
TO PREVENT BLOCK AGES)
OXYGEN SUPPLY (GAS)
PONTOONS
(FLOATING
MECHANISM)
CANAL
WATER LEVEL
PONTOONS
(FLOATING
MECHANISM)
SUPPLY
WATER
WATER
PUMP
VENTURI INJECTION
(WATER/OXYGEN
MIXING SYSTEM)
TWIN DIRECTIONAL
NOZZLE OUTLET
(OXYGEN RICH WATER)
Figure 14.7.
Schematic representation of an oxygenation unit.
(Lloyd & Whiteland
1990
). A near continuous supply (
85%) of oxygen injection
is required in the MSC during the summer, based on the frequency of DO
concentrations falling to less than 4mg L
1
at temperatures of over 16
o
Cas
measured at Trafford Road Bridge (APEM
1990b
). The extremely high SOD and
associated eruption of sediment rafts meant that a certain amount of dredging
was also necessary, as it was unlikely that oxygen enriched water would be able
to penetrate the 0.5m deep sewage-derived sediment layer.
Following the successful trial, designs for the upper MSC oxygenation system
were finalised in February 2000 (APEM
2000
). It was planned that the system
would be operated for a total of 10 years during the summer months when the
poorest water quality in the MSC occurs. Several configurations were con-
sidered but, based upon technical, planning, security and navigational issues,
the five units were located as shown in
Fig. 14.8
. The system comprises a
pipeline which distributes oxygen from a single bulk storage tank located near
Mode Wheel Locks to five oxygen injection units situated at strategic locations
in the Turning Basin (
Fig. 14.8
). Each oxygen injection unit is capable of
supplying 3 Te (tonnes) O
2
per day (125 kgO
2
hr
1
), with an overall maximum
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