About the same time there was an unexplained appearance of some 500 dead Reeve's Terrapins in Tai Tam Tuk reservoir, but comprehensive tests indicated that the quality of the stored water was normal and satisfactory.
Quality of Supply
11.101
A generally satisfactory standard of quality was maintained. Chemical constituents continued to be influenced by the supply derived from Plover Cove reservoir but to a lesser extent as summer inflows reduced the salinity still further from 170 p.p.m. (NaCl) in May to 100 p.p.m. by November, when the total of all dissolved salts stood at 150 p.p.m. Principal characteristics given in parts per million (p.p.m.) were as follows :-
Colony average (1972-73 figures in brackets) Hardness (as CaCO3) 28 (32) 10 Salinity (as NaCl) 10 (168) 40 (56) Total dissolved salts 30 (240) 75 (101)11.102
The bacteriological quality of supply throughout the distribution system continued to be of a very high standard. The target aimed at is absence of coliform organisms in 100 ml. of sample. All 2,971 samples taken regularly from service reservoirs conformed to this standard as did all but one of 2,327 random samples taken from taps connected directly to water mains, and 98.8% of 1,171 samples from taps fed via private storage tanks.
11.103 Fluoridation of supplies, started in 1961 to reduce dental decay in children, continued, the average level being 0.8 p.p.m. fluoride against a nominal target of 1.0 p.p.m.
Most of
11.104 A total of 147 complaints of water quality, of which the majority (84%) were of dirty or discoloured water, were referred to the Unit. These were attributable to excessive corrosion of galvanised iron internal service pipes. The wider use of copper pipes would eliminate this type of trouble, particularly in hot water systems.
11.105
Plover Cove Reservoir
Regular chemical, limnological and biological surveys continued. The chemical quality of the stored and abstracted water remained highly satisfactory and for the third successive year there were no algal blooms, while few fish deaths were recorded during winter months despite lower temperatures than usual. Indications are that in the six years following initial impoundment, the concentration of dissolved salts in the reservoir has now fallen to fairly stable low levels and that a satisfactorily balanced ecology has become established.
125
About the same time there was an unexplained appearance of some 500 dead Reeve's Terrapins in Tai Tam Tuk reservoir, but comprehensive tests indicated that the quality of the stored water was normal and satisfactory.
Quality of Supply
11.101
A generally satisfactory standard of quality was maintained. Chemical constituents continued to be influenced by the supply derived from Plover Cove reservoir but to a lesser extent as summer inflows reduced the salinity still further from 170 p.p.m. (NaCl) in May to 100 p.p.m. by November, when the total of all dissolved salts stood at 150 p.p.m. Principal character- istics given in parts per million (p.p.m.) were as follows :-
Colony average (1972-73 figures in brackets)
Hardness (as CaCO3) Salinity (as NaCl)
10 64
28 (32)
10
168
40 (56)
Total dissolved salts
30 240
75 (101)
11.102
The bacteriological quality of supply throughout the distribution system continued to be of a very high standard. The target aimed at is absence of coliform organisms in 100 ml. of sample. All 2,971 samples taken regularly from service reservoirs confirmed to this standard as did all but one of 2,327 random samples taken from taps connected directly to water mains, and 98.8% of 1,171 samples from taps fed via private storage tanks.
11.103 Fluoridation of supplies, started in 1961 to reduce dental decay in children, continued, the average level being 0.8 p.p.m. fluoride against a nominal target of 1.0 p.p.m.
Most of
11.104 A total of 147 complaints of water quality, of which the majority (84%) were of dirty or discoloured water, were referred to the Unit. these were attributable to excessive corrosion of galvanised iron internal service pipes. The wider use of copper pipes would eliminate this type of trouble, particularly in hot water systems.
Plover Cove Reservoir
11.105
Regular chemical, limnological and biological surveys continued. The chemical quality of the stored and abstracted water remained highly satisfactory and for the third successive year there were no algal blooms, while few fish deaths were recorded during winter months despite lower temperatures than usual. Indications are that in the six years following initial impoundment, the concentration of dissolved salts in the reservoir has now fallen to fairly stable low levels and that a satisfactorily balanced ecology has become established.
125
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