Table 3.1 Summary of Water Quality Objectives for the North Western WCZ
|
Parameter |
Objective |
Part(s)
of Zone |
|
Aesthetic Appearance |
Discharge shall not cause
objectionable odour or discolouration No tarry residue, floating wood, articles made
of grass, plastic, rubber or any
other substance Mineral oil not visible on the
surface. Surfactants shall not give rise to a lasting foam No recognizable sewage-derived debris No floating, submerged or semi-submerged
subjects likely to interfere with the free movement or damage of material Not to contain substances which settle
to form objectionable deposits |
Whole
Zone Whole
Zone Whole
Zone Whole
Zone Whole Zone Whole Zone |
|
E. coli |
Annual geometric mean not to exceed
610/100 mL Geometric mean not to exceed 180/100
mL during March to October inclusive in 1 year; sample should be taken at
least 3 times in 1 calendar month at intervals of between 3 to 14 days Geometric
mean of the most recent 5 consecutive samples taken at intervals of between 7
and 21 days not to be less than 1/100 mL Geometric mean of the most recent 5
consecutive samples taken at intervals of between 7 and 21 days not to exceed
1000/100 mL |
Secondary contact recreation subzones Bathing beach subzones Tuen Mun (A) and Tuen Mun (B) Subzones
and Water gathering ground subzones Tuen Mun (C)
Subzone and other inland waters |
|
Colour |
Not to exceed 30 Hazen units Not to exceed 50 Hazen units |
Tuen Mun (A) and Tuen Mun (B) Subzones
and Water gathering ground subzones Tuen Mun (C) Subzone and other inland
waters |
|
Dissolved Oxygen within 2 m of seabed |
Not less than 2 mg/L for 90% samples |
Marine waters |
|
Parameter |
Objective |
Part(s)
of Zone |
|
Depth averaged Dissolved Oxygen |
Not less than 4 mg/L for 90% samples Not less than 4 mg/L |
Marine waters Tuen Mun (A), Tuen Mun (B) and Tuen
Mun (c) Subzones, Water gathering ground subzones and other inland waters |
|
pH value |
Within the range 6.5 to 8.5 units;
change due to human activity not to exceed 0.2 unit Within the range 6.5 – 8.5 units Within the range 6.0 - 9.0 units Within the range 6.0 to 9.0 units for
95% of samples collected during the year; change due to waste discharge not
to exceed 0.5 unit |
Marine waters excepting Bathing Beach
Subzones Tuen Mun (A), Tuen Mun (B) and Tuen
Mun (c) Subzones, Water gathering ground subzones Other inland waters Bathing Beach Subzones |
|
Temperature |
Change due to waste discharge not to
exceed 2oC |
Whole zone |
|
Salinity |
Change due to waste discharge not to
exceed 10% of natural ambient level |
Whole zone |
|
Suspended solids |
Waste discharge not to raise the
natural ambient level by more than 30%, nor cause the accumulation of
suspended solids which may adversely affect aquatic communities Annual median not to exceed 20 mg/L Annual median not to exceed 25 mg/L |
Marine waters Tuen Mun (A), Tuen Mun (B) and Tuen
Mun (C) Subzones, Water gathering ground subzones Other Inland waters |
|
Un-ionized ammonia |
Annual mean not to exceed 0.021 mg/L |
Whole zone |
|
Nutrients |
Not to be present in quantities that
cause excessive growth of algae or other aquatic plants Annual mean depth-average inorganic
nitrogen not to exceed 0.3 mg/L Annual mean depth-average inorganic
nitrogen not to exceed 0.5 mg/L |
Marine waters Castle Peak Bay Subzone Marine waters excepting Castle Peak
Bay Subzone |
|
5-Day Biochemical Oxygen Demand |
Not to exceed 3 mg/L Not to exceed 5 mg/L |
Tuen Mun (A), Tuen Mun (B) and Tuen
Mun (C) Subzones, Water gathering ground subzones Other Inland waters |
|
Parameter |
Objective |
Part(s)
of Zone |
|
Chemical Oxygen Demand |
Not to exceed 15 mg/L Not to exceed 30 mg/L |
Tuen Mun (A), Tuen Mun (B) and Tuen
Mun (C) Subzones, Water gathering ground subzones Other
Inland waters |
|
Toxic Substances |
Not to be present at levels producing
significant toxic effect, carcinogenic, mutagenic or teratogenic effects in
humans, fish or any other aquatic organisms, with due regard to biologically
cumulative effects in food chains and to interactions of toxic substances
with each other Not to cause a risk to any beneficial
use of the aquatic environment |
Whole zone Whole zone |
|
Phenol |
Not to be present in such quantities
as to produce a specific odour, nor to exceed 0.05 mg/L as C6H5OH |
Bathing beach subzones |
|
Turbidity |
Not reduce light transmission
substantially from the normal level |
Bathing Beach Subzones |