General view showing the inlet measuring flume, accelator and, in the background, the filter beds. Chemical feed pipes to the inlet flume can be seen just beyond the throat.
been provided at the site for future extension and sites have been reserved elsewhere in the area for further ser- vice reservoirs so that the system as a whole can be extended and ex- panded as and when required in the future.
Apart from providing an adequate supply, the aim has also been to give water of the same high standard of quality as is enjoyed in the urban areas of the colony. To ensure the maintenance of this standard a labora- tory for the Waterworks Chemist's staff has been included in the ad- ministration building, where regular tests will be made of the water at different stages in the purification process.
Work on the scheme has progressed in stages. First the forming of the site for the treatment works and ser- vice reservoir was put in hand. This involved the excavation of 325,000 cu. yd. of material of which 65,000 cu. yd. was solid rock. This excavated material was used as filling for the Tai Po reclamation. Work on the construction of the service reservoir and the laying of trunk mains was then started. Meantime the design and specifications for the treatment works was undertaken and tenders invited for the filtration plant.
On completion of the service reser- voir and trunk mains early in 1967 this part of the system was put into service, and temporary arrangements were made to clarify and chlorinate the water going into the reservoir, but of course it remained unfiltered; the quantity available and the relia- bility of supply were, however, greatly improved. Simultaneously the cons-
truction of the treatment works was begun, this being divided into two parts, namely the civil engineering works and the subsequent provision, erection and commissioning of the specialised plant.
The basic design of the civil en- gineering works was carried out by Waterworks staff in conjunction with the plant supplier, but the design of the administration building's elevation was prepared, in accordance with nor- mal P.W.D. practice, in collaboration with the Architectural Office, with one proviso to meet the wishes of the local people which was that for "fung shui" reasons the building should be green in colour. This has in fact resulted in an appearance both pleas- ing and restful to the eye.
TO SERVICE
36′′E FRESH mớÈn pee
TH
GAUGE BASIN
CHEMICAL HOUSE
CHEMICAL
CHEMICAL PIPES
Fig. 1. Tai Po Tau works general layout
The filter station began operation early in May 1968.
Treatment plant
The specification for the treatment works plant called for a conventional purification system comprising an inlet measuring flume, a clarifier and rapid gravity sand beds together with chem- ical dosing equipment and controls. The sand beds were to be cleaned by a combined air-scour and back-wash system which is common in plant of British manufacture but not quite so widely used in other parts of the world. The tenders were to be evaluat- ed on the basis of the overall estimated cost of plant, civil engineering works and site formation and, since the site involved very heavy excavation, it was clear that in this particular case a com- pact layout was desirable.
The successful tenderer was Infilco (Australasia) Pty. Ltd. of Australia, (a subsidiary of an American firm of plant manufacturers), with their Greenleaf filter. Since this plant in- cluded several features which were, as far as the Hong Kong Waterworks was concerned, rather unusual, en- quiries were made in Canada, the USA and Australia to find out wheth- er there were likely to be any operat- ing problems which would render the plant unsuitable for the colony. The replies to these enquiries were very encouraging and the contract was therefore awarded to Infilco.
Treatment processes
Figure 2 shows the sequence of operations as water passes through the plant, the process being as follows:
02
FLOW MEASURING FLUME
GREENLEAF FILTERS
FROM TU PO TAU
PUMPING STATION
38
Far East BUILDER, December 1968
Page 40Page 41
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