The purity of the water was maintained at a high standard, the majority of samples tested shewing B. Coli absent in 100 c.e.
Some 11,147 million gallons of water were Altered at eleven filtration plants. During the year samples of water were examined regularly by the Government Pathologist and by the Government Chemist.
The total quantity of water consumed during the year was 6,550.16 million gallons on the Island and 4,609.49 million gallons on the Mainland (excluding New Territory Villages), à grand total of 11.159.65 million gallons. Included in the Island consumption are 2,576.89 million gallons supplied from the Mainland which is 39.4% of the total Island consumption. The main work carried out under this sub-head was on the Eastern Filters Conversion Scheme which comprises the modernisation of the filtration and distribution of the Tytam Valley water. The works in hand comprise the first stage, namely, the erection of the new filters at Eastern, the new pumping station and the conversion of the Bowen Road cunduit. Contract drawings for the Rapid Gravity Filters and pumping station at Eastern were put in hand and in September Contract No. 37 48 for $790,401.50 was signed with Messrs. Tung Shan & Company,
For the construction of Bowen Road main, Contract No. 149 for $166,650.00 was signed in February 1949 with Messrs. Fook Lee & Company for the manufacture of vibrated concrete pipes with rubber ring joints for the curves. A separate Contract No. 15:49 for $513,525.00 was made with Messrs. Wan Hin & Company for trenching and concrete work and for transport of the pipes.
The installation and testing of the third electrically driven Allen replacement pump, referred to in para. 235 of last year's report, was satisfactorily completed at Garden Road Pumping Station. For the Eastern Pumping Scheme a 40 BHP Diesel engine was purchased."
By courtesy of the Water Authority we are able to give the following brief description of how the plant operates and trace the flow of water through the system. This scheme comprises an 11 million gallons per day modern Filtration plant, a pumping station and European and Chinese Staff Quarters. A general view of the whole installation is shewn on Photograph No. 1 with a view of the Filter house proper in Photo No. 9.
The object of the scheme is to concentrate in one up to date plant the filtration of the water from the Tytam group of reservoirs. This not only means an improvement in the quality of the water supplied to the public, by the elimination of the old inefficient slow sand filters at Eastern End Albany, but also simplifies control of the distribution of the water to various areas. On the sites of the Slow Sand Filters it is intended to build much needed additional service reservoirs
Photo No. 7.
The channels forming part of the filter beds.
Photo No. 6.
F
Some of the reinforced concrete filter beds,
to hold filtered water. The existing filtered water storage is inadequate to deal with peak load draw-off in summer, and does not provide sufficient reserve to deal with fires, break- down of pumps etc.
Raw water is fed to the Filters from the Tytam Tunnel via the conduit in Tai Hang Road. In the background of Photo No. 3 can be seen the gauge basin where the water enters the Filter House, the rate of flow being registered on the "Fluxograph" seen on the right. On the left of this photo is the Lime mixer from which a predetermined dose of lime in solution is added to the raw water. Photo No. 5 shews the alumina mixing tanks from which a controlled dose of this material is also applied to raw water. The water then passes through R.C.C. conduits to the 22 filter beds some of which are seen in Photo No. 6.
The reaction of the lime and alumina causes rapid coagula- tion of the impurities in the water in the filter beds, and rate of filtration is thus speeded up by chemical means and is some 90 times faster than in slow sand filter beds, with consequent saving in the area of filter required. The rate of clogging of the beds is, of course, correspondingly more rapid but this is overcome by pressure cleaning of the beds. This cleaning is accomplished by blowing compressed air up through the sand followed by wash water which collects the coagulated matter extracted from the raw water and carries it off to a drain via the channels seen on Photo No. 7. The whole process of cleaning a bed occupies only a few minutes whereas it takes days to clean a slow sand filter by manual labour. The compressed air containers can be seen on the left of Photo. No.
8.
Filtered water from the beds is collected into a central clear water channel under the floor of the central gallery seen on Photo. No. 4. Here also are situated various control valves, and "Rate of Flow" Indicators which shew the rate of filtration in each bed. When the rate of flow reaches a fixed minimum the operator knows it is time to wash the bed. From the clear water channel the filtered water, after chlorination, is fed by gravity through one R.C.C. conduit and one cast iron pipe line to the pump house shewn on Photo. No. 2 and or to an adjacent service reservoir which supplies the Wong Nei Chong and Eastern areas of Hong Kong. From the pump house water can be pumped to Service Reservoirs at Jardines Lookout (for Repulse Bay), Tai Hang, Middle Gap and Mt. Cameron, Bowen Road (for Wanchai), Albany (for the central mid levels), and Elliot (western district). The pumps are driven by Electric motors (2) Diesel engines (2) and water turbines (4). The water power for the turbines is derived from the head between the clear water channel in the filter house and the Eastern Service Reservoir.
Photo No. 8 & 9.
Two views of the filter house.
11
THE FEU F?!
No comments yet.
Private notes are available after approval.