Ngau Tam Mei Water Treatment Works (¤û¼æ§ÀÂo¤ô¼t) -
Construction of Treatment Works, Pumping Station and
Primary Service Reservoir
The Ngau Tam Mei Treatment Works shall be capable of producing 230,000,000 litre/day of treated water.
Process units include four trains of pre-ozone contactors, four trains of carbon contact basins, rapid mix tanks and flocculation basins, 12 trains of sedimentation basins, 12 first stage gravity filters, 4 trains of intermediate ozone contactors and 12 second stage gravity biological filters.
Ozone Facilities
Flocculation Basins
Sedimentation Basins
Filters
Sludge Treatment
Alum System
Chlorine System
Lime System
Polymer System
Fluoride System
Powdered Activated Carbon System
Potassium Permanganate System
Ammonium sulphate and Sodium Phosphate System
A control and monitoring centre, including computerized SCADA system and central operator consoles, shall be connected to the treatment works local panels via duplicated data highway, and connected to various control consoles throughout the treatment work
s and remote site control consoles via an I/O rack. The system shall provide centralised monitoring of the treatment and pumping plants at Ngau Tam Mei as well as monitoring of equipment located at remote sites.
Process Units
The ozone facilities shall provide pre-ozonation of the raw water and intermediate ozonation of the settled water for disinfection. Hydrogen peroxide will be used to quench excess ozone.
Tapered flocculation consisting of three basins in series, are located downstream of each of the rapid mix trains. Each basin is equipped with a variable speed vertical turbine flocculator capable of providing a tapered flocculation designed to treat diff
erent raw water conditions.
Each sedimentation basin contains three trays to provide a long and narrow path for floc settling. Chain and flight collectors are installed on the bottom and middle trays to facilitate the collection and withdrawal of alum sludge.
Twelve first stage and twelve second stage gravity biological filters shall provide filtration of water.
Two gravity thickeners shall be provided for treating alum sludge collected from the sedimentation basins. Supernatant from the thickeners shall be recycled to the head of the plant via the washwater equalization tanks. On-site facilities for sludge treat
ment shall consist of a sludge thickening process by gravity thickener in tanks and dewatering by filter press to produce sludge cakes for transportation and disposal at a landfill site.
Chemical Facilities
Alum (Aluminium Sulphate) solution to be feed into the works for
flocculation.
Chlorine shall be used for primary and secondary disinfection and for intermittent algae control in the pretreatment basins and filters. Evaporators and chlorinators are used in the production of chlorine solution, while the emergency chlorine scrubber sy
stems are used to handle chlorine leaks up to one tonne.
Hydrated lime (Calcium Hydroxide) shall be used mainly in the control of
pH of the treated water.
Separate polymer systems shall provide coagulant aids and filter aids for water and sludge treatment.
A fluoride system shall provide fluoride solution to the filtered water.
Powdered Activated Carbon shall be fed to raw water to provide odor and colour removal.
A potassium permanganate preparation and feeding system shall be used to oxidize iron and manganese when the ozonation facilities are not used.
Systems shall provided ammonium sulphate and sodium phosphate solution to maintain biological activity in the second stage filter.
Control System
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