SECTION
5 ASSIMILATIVE CAPACITY CAPITAL STOCK
5.2 |
Assimilative
Capacity of Marine Waters |
|
|
|
5.2.4 |
Sustainability
Appraisal |
|
|
|
5.2.4.1 |
Due
to the unparalleled levels of population
and economic growth which Hong Kong has
experienced since the late 1960s, and the
heavy reliance on marine waters as the receiving
medium for liquid, and sometime solid, wastes,
there has been a progressive deterioration
in Hong Kong's marine water quality. This
trend has been accompanied by an accelerating
programme of water pollution and dumping
control strategies and wastewater collection
and treatment systems which has served to
offset an otherwise widening gap between
pollutant inputs and the marine environment's
ability to accommodate these inputs. However,
it is recognised that infrastructure to
enhance assimilative capacity as a stand-alone
solution to marine pollution may not be
sufficient to maintain the natural capital
stock without supporting measures to address
the fundamental causes of pollution. (Key
sustainability issues for the marine assimilative
capacity are shown in Figure
5.2e).
|
|
|
5.2.4.2 |
As
the assimilative capacity of the marine
environment in Hong Kong is not presently
well-understood, it is not possible to quantitatively
address whether the assimilative capacity
has already been exceeded or the extent
to which additional discharges can be absorbed.
Nevertheless, using statutory Water Quality
Objectives as a guideline, it is clear that
the beneficial uses of certain waterbodies
including Deep Bay, Victoria Harbour and
Tolo Harbour have already been compromised
by a surfeit of uncontrolled discharges.
|
|
|
5.2.4.3 |
There
are two types of possible responses to address
current and future pressures on marine assimilative
capacity. The first can be broadly characterised
as "output" responses, or those
which act on the wastes which are already
captured by the existing system controlling
collection and treatment of the wastestreams
destined for marine waters. In Hong Kong
there are many options for implementing
improved "output" strategies including:
- improving
the level of treatment, and the percentage
treated, of collected flows through existing
or new sewage treatment works;
- locating
outfalls for treated or untreated marine
discharges in areas of high dispersion
capacity;
- ensuring
that the natural flushing characteristics
of receiving waterbodies are maintained
by avoiding physical barriers to dispersion
and excessive abstraction or diversion
of clean, natural flows;
- maintaining
standards for permitted marine discharges
through monitoring of waterbodies to ensure
unacceptable impacts are not occurring;
- ameliorating
areas of extreme contamination through
removal of sediment (eg remedial dredging
or in situ improvement), diversion of
inputs (eg effluent export); and
- co-operating
on a regional level to maintain and improve
ambient marine water quality in areas
bordering marine waters.
|
|
|
5.2.4.4 |
The
second type of response is characterised
by its focus on "inputs", ie reducing
the flows and loads entering wastestreams
destined for marine waters through waste
reduction measures similar to those discussed
in Section 3.5.4 - Solid Waste. Under this
approach, the incentives are provided to
reduce contributions to the existing waste
management system and/or to stem unauthorised
use of marine waters for disposal. "Input"-focused
options include:
- providing
a more extensive sewerage network to collect
a greater proportion of wastewaters thereby
reducing the number of direct discharges
to coastal waters;
- heightening
enforcement of discharge licence conditions
and prosecution of illegal disposal activities;
- promoting
technologies which can reduce the load
of pollutants generated through cleaner
production processes;
- implementing
full cost recovery for wastewater services
as an extension of the polluter pays principle;
- educating
the public to cease illegal dumping of
waste in marine waters and casual littering
from vessels and in coastal areas such
as beaches; and
- educating
the public and business community in water
conservation and recycling so as to reduce
wastewater hydraulic loads.
|
|
|
5.2.4.6 |
A
sustainable approach to preserving the assimilative
capacity of marine waters will require components
of both "output" and "input"
approaches and, as highlighted in Section
5.2.3, many initiatives of both types are
currently underway. These initiatives will
improve marine water quality but as they are
addressed to specific sources rather than
to cumulative impacts they will not guarantee
that the benefits associated with marine waters,
including assimilative capacity, ecological,
natural resource, recreational, and landscape
natural capital stock values, will be maintained.
In the absence of the scientific information
necessary to quantitatively apply the assimilative
capacity concept as a water quality management
tool, it will be necessary to continue to
adopt a management approach based on in situ
monitoring to assess trends in ambient conditions.
This approach, though retrospective in nature,
if applied consistently (ie ensuring long-term
continuity of data sets) and comprehensively
throughout Hong Kong waters, will provide
a basis for swift identification of adverse
impacts and prompt remedial action. It may
also help to offset increasing wastewater
treatment costs which would otherwise arise
as assimilative capacity is denuded and ever
greater quantities and standards of treatment
become necessary. |
|
|
5.2.4.7 |
Alternatively,
Hong Kong could pursue constructing an assimilative
capacity model of all waterbodies which could
be used to set permitting discharge limits
for polluting activities. When applied in
conjunction with feedback from monitoring
data, such a model would help to provide an
explicit link between the levels of individual
discharges and the resulting quality of the
receiving waterbody, and allow for more proactive
management. |
|
|
|