Ponder this engineering marvel. The Stonecutters Island Sewage Treatment Works stands before us. It is a testament to Hong Kong’s commitment to a sustainable future. This isn’t just any sewage plant. It’s one of the largest, most compact facilities of its kind.
Welcome to the Stonecutters Island Sewage Treatment Works. It is a crucial part of the Harbour Area Treatment Scheme or HATS. HATS dramatically improved Victoria Harbour’s water quality.
Occupying 10 hectares of reclaimed land, Stonecutters Island Sewage Treatment Works is a chemically enhanced primary treatment works. The plant treats about 1.9 million cubic meters of sewage daily from both sides of Victoria Harbour. That’s like processing the equivalent of 1,000 Olympic swimming pools each day.
Think about the scale. The Stonecutters Island Sewage Treatment Works serves up to 5.7 million people. It is located on a site only half the size of Victoria Park. This was achieved by double-decking the sedimentation tanks. This innovative design reduces the plant’s footprint.
The Harbour Area Treatment Scheme is Hong Kong’s largest environmental infrastructure project. It aims to improve Victoria Harbour’s water quality by collecting and treating sewage from both shores.
After the commissioning of HATS Stage 2A, all sewage from both sides of Victoria Harbour is collected. It is treated and disinfected before discharge. Over 99% of E. coli are eliminated. Moreover, 70% of biochemical oxygen demand and 80% of suspended solids are removed from the sewage.
Sewage collected by 17 preliminary treatment works arrives here. It is pumped from deep tunnels to the surface via Main Pumping Station No. 2. This is one of the world’s largest underground sewage pumping stations. The pumping station houses eight mega-size sewage pumps. Each pump can fill an Olympic-size swimming pool in a minute.
Once above ground, the sewage undergoes chemically enhanced primary treatment. Chemicals like ferric chloride and polymer are added. The mixture flows through flocculation tanks. Flocs form and settle in the sedimentation tanks. Sludge collectors remove the sludge. Scum collectors skim off lighter materials. This process removes about 80% of suspended solids and 70% of Biochemical Oxygen Demand.
The treated effluent is disinfected with sodium hypochlorite solution. It then flows through an effluent tunnel for 30 minutes. Finally, it is dechlorinated with sodium bisulphite solution. The treated water is discharged into Victoria Harbour through a submarine outfall.
Odor control is a priority here at Stonecutters Island Sewage Treatment Works. Fiberglass reinforced plastic covers seal the sedimentation tanks and flow channels. An air extraction system collects foul gas. Chemical scrubbers and biotrickling filters treat the gas before it is released.
Sludge dewatering facilities handle up to 1,200 tonnes of sludge per day. Centrifuges increase the solid content of the sludge. Special vessels transport the sludge to T-PARK in Tuen Mun. This minimizes odor nuisance to nearby residents.
“Clean Harbour 1” and “Clean Harbour 2” are the first diesel-electric propulsion container vessels in Hong Kong. They connect to on-shore power supplies when berthed. This achieves zero emissions. These vessels reduce carbon dioxide emissions significantly.
To commemorate the Harbour Area Treatment Scheme, the Drainage Services Department designed a feature wall. It is called “Fish 1989.” It embodies 1,989 fish swimming to form the DSD logo. This represents the department’s commitment to wastewater and stormwater drainage services since 1989.
The Stonecutters Island Sewage Treatment Works stands as a symbol. It is a symbol of Hong Kong’s dedication to environmental protection. It showcases innovative engineering. It ensures a cleaner, healthier Victoria Harbour for generations to come.