General
WATER QUALITY CONTROL SECTION
Senior Waterworks Chemist:
D. L. MAKER, A.R.I.C., P.A.I.W.E.
8.58. This Section is primarily responsible for all matters concerning treatment and quality of Water Authority supplies. It operates a central laboratory at Sha Tin treatment works and a subsidiary laboratory in Kowloon, both fully equipped to carry out chemical and bacteriological examinations of water samples and of miscellaneous materials used in the water industry. Water testing facilities also exist at most of the individual treatment works. During the year 12,995 samples were examined, of which 4,025 were for bacteriological testing. This compared with 10,024 and 3,058 respectively last year.
8.59. The supply to all urban and many rural areas is fully treated by coagulation with alum and lime, rapid gravity filtration, chlorination, pH value correction and fluoridation, quality being maintained to internationally accepted standards.
8.60. Normally the Colony's water supply is classed as very soft and low in mineral salts content. However, there was a marked change in quality in most urban areas when a proportion of water derived from the new Plover Cove reservoir, which still had an appreciable residual salt content in its first year of operation, was pumped into the supply system from October 1967.
8.61. Salinity rose to a maximum of 900 parts per million, expressed as sodium chloride, just below the limit of 990 parts per million suggested by the World Health Organization. When salinity increased above 400 parts per million, most people could detect the salty taste and at first, a very large number of complaints were received. However, criticisms became fewer as the public began to appreciate the need for conservation of fresh water resources and became accustomed to the salinity. Comprehensive monitoring of supplies ensured that at no time did salinity exceed the World Health Organization limit, and the results were published weekly in the press. Associated with the supply of saline water, a secondary change in quality noticed by consumers was the considerable increase in hardness, more soap being required to produce a satisfactory lather.
8.62. The following table illustrates in analytical terms the main differences in characteristics between the saline and normal supplies in the Colony:
98