in addition to the existing Laboratories at Sha Tin and Kowloon on the mainland. The biological unit at Plover Cove Reservoir was also incorporated into the section on 1st August, 1968. The total number of water samples examined increased by 93% over the previous year to 25,033 of which 5,769 were for bacteriological testing.
8.65. All urban and many rural areas are supplied with water which is fully treated at the older treatment works by coagulation with alum and lime followed by rapid gravity filtration, chlorination, pH value correction and fluoridation whilst at the contemporary waterworks designed to deal with water resources subject to pollution, filtration is preceded by sedimentation and additional chlorination.
8.66. Inflows reduced the salinity of water in Plover Cove Reservoir from 2,100 parts per million expressed as sodium chloride (NaCl) in May to a minimum of 460 parts per million by September. Algal activity, which had previously caused some filtration difficulties at the Sha Tin treatment works, gradually declined towards the end of the year. Regular hydrological and biological surveys of the Plover Cove reservoir continued and 660,500 freshwater fish fry were introduced as part of the stocking programme.
8.67. The blending of Plover Cove reservoir water into the system reducing the salinity of water supplied to around 300 parts per million NaCl and hardness to 100 parts per million as CaCO3, was accepted by consumers without adverse comment, in contrast to the previous year when the higher salinities of up to 900 parts per million evoked numerous complaints of salty taste and excessive hardness. During the year 136 complaints of quality were made, 95% being of dirty or discoloured water while objectionable odour or taste accounted for only 2%.
8.68. In connection with the continued fluoridation of supplies which had been started in 1961 the average level of fluoride maintained was 0.86 parts per million compared with a nominal target of 1.0 parts per million, the slight deficiency in dosing being attributable to the poor dry feeding characteristics of chemical available.
8.69. Bacteriological purity of supply was well maintained; the standard aimed at is absence of coliform organisms in 100 ml. Of the 2,445 periodic samples taken from service reservoirs, 99.6% conformed to this standard or better. Random samples were also taken from consumers' premises and public standpipes. 98.7% of the 1,029 samples
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in addition to the existing Laboratories at Sha Tin and Kowloon on the mainland. The biological unit at Plover Cove Reservoir was also incorporated into the section on 1st August, 1968. The total number of water samples examined increased by 93% over the previous year to 25,033 of which 5,769 were for bacteriological testing.
8.65. All urban and many rural areas are supplied with water which is fully treated at the older treatment works by coagulation with alum and lime followed by rapid gravity filtration, chlorination, pH value correction and fluoridation whilst at the contemporary waterworks designed to deal with water resources subject to pollution, filtration is preceded by sedimentation and additional chlorination.
8.66. Inflows reduced the salinity of water in Plover Cove Reservoir from 2,100 parts per million expressed as sodium chloride (NaCl) in May to a minimum of 460 parts per million by September. Algal activity, which had previously caused some filtration difficulties at the Sha Tin treatment works, gradually declined towards the end of the year. Regular hydrological and biological surveys of the Plover Cove reservoir continued and 660,500 freshwater fish fry were introduced as part of the stocking programme.
8.67. The blending of Plover Cove reservoir water into the system reducing the salinity of water supplied to around 300 parts per million NaCl and hardness to 100 parts per million as CaCo, was accepted by consumers without adverse comment, in contrast to the previous year when the higher salinities of up to 900 parts per million evoked numerous complaints of salty taste and excessive hardness. During the year 136 complaints of quality were made, 95% being of dirty or dis- coloured water while objectionable odour or taste accounted for only 2%.
8.68. In connection with the continued fluoridation of supplies which had been started in 1961 the average level of fluoride maintained was 0.86 parts per million compared with a nominal target of 1.0 parts per million, the slight deficiency in dosing being attributable to the poor dry feeding characteristics of chemical available.
8.69. Bacteriological purity of supply was well maintained; the standard aimed at is absence of coliform organisms in 100 ml. Of the 2,445 periodic samples taken from service reservoirs, 99.6% conformed to this standard or better. Random samples were also taken from con- sumers' premises and public standpipes. 98.7% of the 1,029 samples
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