pH value correction, sterilisation with chlorine and fluoridation. No serious treatment difficulties were encountered during the year.
11.111 The Unit initiated studies in connection with the treatment and disposal of waste sludge from Sha Tin Treatment Works (including the recovery and re-use of alum), and the feasibility of using treated sewage effluent for both flushing and irrigation purposes.
11.112 Average dosages and total consumption of principal chemicals used in water treatment are shown in Appendix CC. Expenditure on the purchase of chemicals continued to fall for the second year in succession despite the increase in water consumption, reflecting lower chlorine and alum prices.
Quality of Supply
11.113 In general terms the supply is classified as being soft, low to moderate in mineral salt content and very low in organic matter. Chemical and bacteriological standards continued to be well above those recommended by the World Health Organisation. Information on principal water quality characteristics is given in Appendix CC.
11.114 Discoloured or "rusty" water, due mainly to corroding galvanised iron inside service pipes, continued to be the major cause of complaints of quality by consumers.
General
11.115 CONSULTANTS LIAISON UNIT
Senior Engineer:
IP Yun-wing, M.Sc.(Eng.), B.E., M.I.C.E., M.I.E.Aust.(Acting)
LAI Hon-wah, M.A.Sc., B.Sc.(Eng.), M.I.C.E., M.I.W.E.S., F.G.S.
The Unit is responsible for liaising with consultant engineers engaged on water supply schemes other than desalting. Expenditure during the year amounted to about $222 million.
High Island Water Scheme
11.116 Satisfactory progress of construction of the West Dam was maintained and the dam was substantially completed along with the West Col Dam, spillway and outlet works.
11.117 At the East Dam, leakage through the East Sea Cofferdam was brought under control, excavation was completed and the core of the dam constructed to +6m PD.
11.118 Work on the tunnels was completed except for the installation of the energy dissipator at tower A. Steelwork fabrication for the energy dissipator was complete.
11.119 Mechanical and electrical works were substantially completed and ready for commissioning tests.
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