Refinement of Purified Sewage for Unrestricted Industrial Use
631
coagulant
chlorine if required
LEGEND:
(1) pump I
(2) flow meter
(3) pump 2
(4) flotation tank
(5) solids contact stabilizer
(6) sond filter
Fig. 1.
Flow diagram of proposed pilot plant at S.A.P.P.I. Springs
FULL-SCALE PLANT OPERATIONS
From the data obtained with the pilot plant and to a large extent the experience
gained by the National Institute for Water Research at Windhoek's water reclamation
scheme, a plant to treat 32,000 m
3 /d of Springs purified sewage was designed by SAPPI.
It was erected in 1969/70 at a cost of Rl 59,000, and was commissioned during July
1970.
The layout of this plant is shown in Fig. 2. It consists of the following units:
(a) a 24 in. feeder line; (b) a booster pump; (c) an aeration vessel with a high-speed rotor
at the bottom, operating at 0.6 bar (10 psi) pressure, for full-stream aeration; (d) an air
compressor, consuming 7.5 kW or 10 hp; (e) the flotation tank (capacity 750 m
3 ); (f)
storage tanks for alum and for caustic soda and for polyelectrolyte; (g) auxiliary
equipment such as flow recorders, pH recorders, pressure controller, chlorinator, sludge
tank and pumps.
During the start-up period, the chemical dosage of 140 mg/1 alum as
A1 2 (S04)3.14H 2 0 without polyelectrolyte was applied as in the previous laboratory and
pilot plant-scale tests. The strength of the alum in the storage tank was 525 g/1. The alum
was added as the water entered at the top of the centre compartment of the flotation
tank and NaOH at about 20 mg/1, was added to the clarified water at the outflow launder
as indicated in Fig. 2. Aeration was apparently very efficient; effervescence was observed
over the whole surface of the flotation tank while a small amount of non-dispersed air in
the form of large bubbles escaped at a handhole in the top of the slowly rotating centre
section. At a later occasion, aeration was not as good. An investigation into the efficiency
of aeration revealed that at constant operating pressure and constant throughput the
631
coagulant
chlorine if required
LEGEND:
(1) pump I
(2) flow meter
(3) pump 2
(4) flotation tank
(5) solids contact stabilizer
(6) sond filter
Fig. 1.
Flow diagram of proposed pilot plant at S.A.P.P.I. Springs
FULL-SCALE PLANT OPERATIONS
From the data obtained with the pilot plant and to a large extent the experience
gained by the National Institute for Water Research at Windhoek's water reclamation
scheme, a plant to treat 32,000 m
3 /d of Springs purified sewage was designed by SAPPI.
It was erected in 1969/70 at a cost of Rl 59,000, and was commissioned during July
1970.
The layout of this plant is shown in Fig. 2. It consists of the following units:
(a) a 24 in. feeder line; (b) a booster pump; (c) an aeration vessel with a high-speed rotor
at the bottom, operating at 0.6 bar (10 psi) pressure, for full-stream aeration; (d) an air
compressor, consuming 7.5 kW or 10 hp; (e) the flotation tank (capacity 750 m
3 ); (f)
storage tanks for alum and for caustic soda and for polyelectrolyte; (g) auxiliary
equipment such as flow recorders, pH recorders, pressure controller, chlorinator, sludge
tank and pumps.
During the start-up period, the chemical dosage of 140 mg/1 alum as
A1 2 (S04)3.14H 2 0 without polyelectrolyte was applied as in the previous laboratory and
pilot plant-scale tests. The strength of the alum in the storage tank was 525 g/1. The alum
was added as the water entered at the top of the centre compartment of the flotation
tank and NaOH at about 20 mg/1, was added to the clarified water at the outflow launder
as indicated in Fig. 2. Aeration was apparently very efficient; effervescence was observed
over the whole surface of the flotation tank while a small amount of non-dispersed air in
the form of large bubbles escaped at a handhole in the top of the slowly rotating centre
section. At a later occasion, aeration was not as good. An investigation into the efficiency
of aeration revealed that at constant operating pressure and constant throughput the