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Environmental Functions and Performance
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Our key responsibility is to provide
and operate the drainage, sewerage and sewage treatment
infrastructure in Hong Kong. In 2004, we collected and treated
954 million cubic metres of sewage to achieve a high level
of sanitation. In
delivering the service, we operated 67 sewage treatment
works, 172 sewage pumping stations and low flow interceptors,
43 submarine outfalls, 3 effluent disposal tunnels and maintained
1,506 km of sewers. In flood prevention, we maintained 2,514
km of drainage channels and drains and 26 flood pumping
schemes. In the continuous improvement of the drainage and sewage treatment
infrastructure, we are running 63 contracts to construct
new works as well as to maintain and upgrade existing facilities.
Rising public health standard and
increasing environmental effectiveness of sewage treatment are put in
place. Towards improving the water quality of Victoria Harbour, the
treatment of sewage from some 3 million people equivalent has been
upgraded since 2001 from a simple screening process to a process beyond
the conventional primary treatment, namely Chemically Enhanced Primary
Treatment (CEPT) under the Harbour Area Treatment Scheme (HATS) Stage I.
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Sewage
treatment in Hong Kong
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2002
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2003
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2004
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Treatment level provided
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(Million m3)
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(Million m3)
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(Million m3)
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Percentage Share
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Screening and degritting
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274
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275
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284
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29.8%
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Primary treatment
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4
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4
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4
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0.4%
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Chemically Enhanced Primary Treatment
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485
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508
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507
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53.1%
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Secondary biological treatment
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148
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156
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159
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16.7%
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Total
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911
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943
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954
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100.0%
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Performance Measures
We constantly introduce sound management practices
and the best available technology to make our operations
more energy efficient, more sustainable and more effective
in pollution reduction. Considerable achievements
were made in 2004. We removed 87,910 tonnes of BOD,
121,003 tonnes of Suspended Solids and 4,889 tonnes
of Nitrogen from entering our receiving waters. We collected 8.2 million m3 of methane generated from
anaerobic digestion of sewage sludge in our works
to generate heat and electricity for plant use and
hence help reduce demand on electricity or fossil fuel. The surplus gas is flared
to reduce the impact on global warming, as methane
is a strong greenhouse agent which is 21 times more
powerful in trapping heat in the atmosphere than Carbon
Dioxide does.
The removal of pollutants, resource consumption and
environmental emissions are summarized in the following table.
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Sewage
treatment facilities in Hong Kong
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Achievements, Resource Consumption and Environmental
Emissions in 2004
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Sewage treatment
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2003
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2004
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Quantity
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Total Flow
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(Million m3)
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943
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954
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BOD (tonnes)
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In
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124,157
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116,409
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Removed
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93,654
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87,910
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Out
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30,503
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28,499
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SS (tonnes)
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In
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155,693
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142,567
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Removed
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129,563
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121,003
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Out
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26,130
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21,562
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Total N (tonnes)
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In
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5,906
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6,464
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Removed
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3,770
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4,889
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Out
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2,136
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1,575
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Waste Produced
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Screenings
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m3
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20,705
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19,220
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Grit
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m3
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7,078
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6,738
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Dewatered sludge
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tonnes
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305,660
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288,757
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Gas emission
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Greenhouse gas
recovered
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Million m3
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9.3
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8.2
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Resource
Consumption
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Power
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KWh
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231,002,217
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210,714,011
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Chemicals
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tonnes
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13,235
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13,154
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tonnes
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86
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209
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tonnes
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72
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87
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tonnes
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2,912
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2,799
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tonnes
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682
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562
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tonnes
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-
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2,168
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tonnes
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-
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3,503
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Effectiveness
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BOD removed
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75.4%
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75.5%
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SS removed
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83.2%
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84.8%
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Total N removed
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63.8%
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75.6%
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Power consumed
(KWh per m3 sewage treated)
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0.245
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0.221
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Power consumed
(KWh per tonne BOD removed)
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2,344
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2,397
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Office
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2003
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2004
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Paper consumed
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Reams
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17,300
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18,810
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Paper consumed
per staff
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Reams
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8.9
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9.7
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Envelopes
consumed
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number
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148,089
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97,700
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Waste paper
recycled (1)
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kg
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9,290
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12,360
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Power (2)
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KWh
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159,505
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158,379
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(1) Estimates based
on data for the whole Revenue Tower
(2) Only for the Sewage Services Branch office at
Guardian House where individual meter was provided
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Sewer and Drainage
Maintenance
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Quantity
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Drains, channels
and
water courses cleansed
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km
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513
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629
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Silt removed
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m3
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59,946
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279,909
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Sewers cleansed
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km
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614
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627
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Silt removed
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m3
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6,351
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4,956
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Abbreviations
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BOD
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Biochemical Oxygen
Demand
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SS
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Suspended Solids
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Total N
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Total Nitrogen
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KWh
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Kilowatt hour
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