Sludge digestion tanks showing concreting access gallery
Excess flow over the designed cap- acity of the west works can also be passed through a 45 in. dia, intercon- nection to the east works; this cross connection is at present being used to feed sewage from Toa Payoh, where the first flats have been occupied, in- to the west works.
Work on the three-mile effluent out- fall involved the construction of 1,300
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ft. of 66 in. dia. and 5,400 ft. of 60 in. dia. r.c. pipes, 1,500 ft. of 60 in. dia., 7,000 ft. of 51 in. dia, and 2,300 ft. of a twin 45 in. dia. steel pipes.
Effluent outfall
The concrete pipes used were manufactured in sulphate resisting ce- ment and, as for the gravity sewers, are spigot and socket pipes with rub-
ber rings. In the 60 in. dia. section of the outfall, a trial use of 6 x 10 ft. long p.v.c. lined r.c. pipe was in- corporated to test the use of this latest method of protection against corro- sion in sewers.
The steel pipes used are manufac tured in 25 ft. lengths with spigot and socket and welded joints and comply with B.S.534:1934. Internally, the pipes are lined with 1 in. thick cement fondu and wrapped externally.
Sludge mains
The sludge main to Serangoon Sludge Disposal Works is 17,000 ft. long and is constructed in asbestos cement pipes. The cement asbestos pipes are manufactured locally and comply with B.S.486:1956.
Design and supervision
The design of the pumping stations, rising mains, gravity sewers and treat- ment works were carried out by J.D. & D.M. Watson, Design of the efflu- ent outfall and sludge mains to Ser- angoon from the treatment works was carried out by the Public Work De- partment.
In all cases, supervision and ad- ministration of the contracts were un- dertaken by the Public Works De- partment. At the peak stage of con- struction, the complement of site staff comprised two resident engineers, five. assistant resident engineers, five clerks of works and 30 supervisors.
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Sewage digestion tanks and effluent washwater tower
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Far East BUILDER, July 1968.
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