WATER:
WATER QUALITY
Core Notes for the First Lecture of Module 3 of the Course
“Environmental Engineering – Sustainable Development in Coastal Areas”
Compiled by:
Dr Liz Day
Freshwater Consulting Group
lizday@mweb.co.za
in conjunction with:
Mr Gareth McKonkey
DWAF
The material for this Lecture also includes:
ƒ Case Study
ƒ Newspaper articles
ƒ Self-test
ƒ Sources of Reference
ƒ Additional material
Cape Peninsula University of Technology (CPUT)
Cape Town, South Africa
2006
Available to Distance Learners on www.dlist-benguela.org
Environmental Engineering – Sustainable Development in Coastal Areas
Module 3 Water: Core Notes for Water Quality Lecture
Table of Contents
1
INTRODUCTION................................................................... 3
2
WATER QUALITY AND FRESHWATER ECOSYSTEMS.............. 3
2.1
Different types of aquatic ecosystems....................................................3
2.2 Important functions and services provided by rivers and wetlands ........4
2.2.1 Services provided by rivers ................................................................... 4
2.2.2 Functions and services of wetlands ........................................................ 4
2.3 Understanding the processes that drive aquatic ecosystem functions ....5
2.3.1 Processes and functions ....................................................................... 5
2.3.2 How do these processes apply at the level of different rivers? .................... 7
2.3.3 What happens at a catchment level? ...................................................... 9
2.3.4 How do ecosystem processes apply at the level of different wetland types?.. 9
3
WATER QUALITY IN SOUTH AFRICA .................................. 10
3.1
What is water quality? .........................................................................10
3.2
What happens when water quality changes - and does it matter? ........10
3.3
Natural water quality ...........................................................................11
3.4 What causes changes in water quality? ................................................12
3.4.1 Changes in water quantity .................................................................. 12
3.4.2 Changes in river morphology............................................................... 13
3.4.3 Pollution........................................................................................... 14
4
POLLUTION ....................................................................... 14
4.1 Types of pollution ................................................................................14
4.1.1 Pollution categorised by Source ........................................................... 14
4.1.2 General impacts of pollution on the Receiving Environment (Resource) ..... 15
4.1.3 Specific impacts of pollution on ground and surface water ....................... 15
4.1.4 Assessing the risks of pollution ............................................................ 20
4.2 Pollution as a result of dense settlements ............................................20
4.2.1 Water quality problems in dense settlements......................................... 20
4.2.2 Four waste streams ........................................................................... 21
4.2.3 Physical, Institutional and Social causes of pollution in dense settlments ... 21
4.2.4 The Production, Delivery, Transport and Use continuum .......................... 22
4.2.5 Waste production in Settlements ......................................................... 22
4.2.6 Waste delivery in settlements ............................................................. 23
4.2.7 The pollution cycle............................................................................. 24
4.3
Balancing services and affordability .....................................................24
5
WATER QUALITY STANDARDS AND FRESHWATER
ECOSYSTEMS ............................................................................ 26
6
REFERENCES REFERRED TO IN THESE NOTES .................... 27
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Module 3 Water: Core Notes for Water Quality Lecture
1
Introduction
Management of our freshwater resources is one of the most critical issues for South
Africa in the 21st Century. South Africa is on the whole a very arid area, with much
of the country receiving less than 500mm of rainfall per year (Davies and Day 1998).
Moreover, in most areas, evaporation rates are higher than rainfall, and in these
areas, any rain that falls on the ground quickly evaporates, re-entering the
atmosphere. Further complicating matters, rainfall tends to be highly seasonal, and
often erratic, in distribution. It is against this background that the water
requirements of a rapidly increasing (and urbanising) population must be met, in
terms of both water quality and water quantity. At the same time, the needs of the
environment itself cannot be ignored, even if only for the reason that South Africa’s
people ultimately rely on their natural environment to provide them with the
resources they need for daily life. Not only will an impacted freshwater resource fail
to provide habitat and resources to plants and animals, but it will also fail to meet
the requirements in terms of water quality and quantity of the people that depend
upon it.
This module aims to provide first a brief overview of the diversity of freshwater
ecosystems, how they function and the services that many of them provide to
humans. It is only in the light of this information that the implications of different
effects on water quality or flow regimes can be understood, in terms of both human
and ecosystem health. These implications are touched on here. Students are
however urged to supplement this core course material with additional reading (see
Section 7).
2
Water quality and freshwater ecosystems
2.1 Different types of aquatic ecosystems
In this module, freshwater ecosystems are divided into two different categories –
wetlands, and rivers. It should be remembered, though, that wetlands and rivers
are often interlinked, with many rivers either feeding and/or being fed by associated
wetlands. In addition, this simplified distinction ignores a third vitally important
freshwater resource – groundwater. The importance of groundwater in the
management of surface water resources is being realised more and more, and
although this module will not cover this issue further, its importance should be borne
in mind.
Box 1: What is a wetland?
Wetlands are defined in terms of:
ƒ soil type (they have soils that are characteristically waterlogged for part or all of the time)
ƒ biota (animals and plants have adaptations that allow them to survive specific wetland
conditions; e.g. periodic water-logging
ƒ hydrology
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Examples of different wetlands include:
ƒ lakes
ƒ salt marshes
ƒ coastal lakes
ƒ artificial impoundments / “dams”
ƒ marshes
ƒ swamps
ƒ riverine wetlands / vleis
ƒ pools, pans and ponds
2.2 Important functions and services provided by rivers and
wetlands
Freshwater ecosystems are often important habitats for communities of plants and
animals that are found only in these ecosystems. In addition to providing habitat,
they also have numerous other functions, some of which are also of great value to
humans.
2.2.1 Services provided by rivers
In a broad context, rivers drain the landscape; they leach solutes from underlying
rocks, shape the landscape, transport sediments to the coast, act as natural barriers
(e.g. border lines between different countries) and provide important habitats to
sometimes unique communities of plants and animals. These processes result in the
provision of numerous services, many of which are valuable to humans:
ƒ Rivers distribute water, used for drinking (humans, their livestock and other
animals); irrigation; hydroelectricity
ƒ Riverine organisms purify water, for example by breaking down nutrients and other
organic material
ƒ Rivers provide silt to floodplains – many farming communities as well as natural
ecosystems rely on the annual provision of fertile, organically rich sediment to
alluvial floodplains
ƒ Rivers provide a life support mechanisms for many living resources (e.g. fish,
reeds; medicinal plants)
ƒ Large rivers can act as transport corridors, allowing boats to pass along their
reaches (e.g. Zambezi River; Mississippi River in USA)
2.2.2 Functions and services of wetlands
In addition to important attributes such as the provision of habitat to often-unique
communities of animals and plants, many wetlands (even, man-made or impacted
systems) also provide a diverse array of functions, some of which can be of
tremendous human benefit. These functions include:
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ƒ retention of water in wetland soils and hence:
o
improvement in soil structure
o
reduction in drying and subsequent erosion of soil
o
maintenance of moist habitats during lowflow periods;
ƒ flood attenuation – effected by retention of flood waters in wetland soils, and
reduction of flood velocities, which occurs when flood waters flow through wide,
vegetated areas;
ƒ improving the quality of water flowing into rivers, by uptake and absorption of
nutrients and other contaminants often found in surface runoff;
ƒ trapping sediment and reducing erosion of stream channels;
ƒ provision of natural resources (e.g. reeds for weaving; fish; other animals for food;
medicinal plants; clean water);
ƒ educational and tourism resources;
ƒ provision of habitat to wetland-associated animals and plants, many of which rely
exclusively on these areas for breeding, feeding or nursery areas;
ƒ provision of corridors for movement between terrestrial natural areas, or along
river systems.
Did you know?
Artificial wetlands are being constructed more and more frequently, because of the value of
the functions they are able to perform – for example, purification (polishing) of sewage
effluent or stormwater runoff.
Box 2: Wetland conservation
Despite the immense ecological, economic and educational value of wetlands, it has been
estimated that over half of South Africa’s wetlands as a whole have already been destroyed
and lost, while those that remain are among South Africa’s most threatened natural areas
(Noble & Hemens 1978; Begg 1986).
South Africa is a signatory to the Ramsar Convention, an international treaty aimed at the
conservation of wetland habitats (Cowan 1995). This convention binds members to a set of
criteria aimed at the conservation of wetland ecosystems. These criteria include: stemming
the loss of wetlands, promoting the wise use of all wetland areas and promoting the special
protection of listed wetlands.
2.3 Understanding the processes that drive aquatic ecosystem
functions
2.3.1 Processes and functions
Under natural conditions, the ways in which aquatic ecosystems (rivers and
wetlands) function are determined by a number of processes. We need to
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understand these processes, in order to understand the implications for aquatic
ecosystems of various human-induced changes, and the indirect consequences of
these changes for human communities.
Aquatic ecosystems are both driven, and characterised by:
ƒ Hydrological and physical processes. These include factors such as current
(the flow of water); discharge (the total amount of water flowing down a river or
through a wetland); the movement of dissolved substances along the river; the
movement of suspended materials along the river (these materials vary from fine
silt to boulders). In addition, variations in the frequency (how often it occurs),
magnitude (how big it is) and duration (how long it lasts) of different kinds of flows,
from low flows to floods, also affect the way rivers and/ or wetlands function and
their properties.
Interference with any of the above processes may have implications for the
structure of river beds (geomorphology); the ability of the river to carry out
cleansing functions, such as the removal of natural and human-generated waste;
the type and health of riparian (associated with the riverine environment)
vegetation and the structure and variety of habitats for riverine organisms.
ƒ Chemical processes: these include weathering (e.g. active weathering of rocks
allows dissolved solids to be incorporated into stream flow); precipitation and
crystallisation, which affect the concentration of different salts in surface water
(e.g. where precipitation is high and evaporation (and hence crystallisation) rates
are low, water will have relatively low concentrations of dissolved solids. Even
under natural conditions, major variations in chemical processes can occur in time
and with different climates (because of changes in hydrology, temperature etc).
Different processes also occur in different chemical environments. For example,
some compounds are toxic under certain chemical conditions, and not under other
conditions. Ammonia exists, for example, in two forms - ionised, as the ammonium
ion, or in its free, un-ionised form, as ammonia. The latter is highly toxic to aquatic
organisms, even at very low concentrations. The proportion of each form at a
given time is a product of both water temperature and pH, with the ionised
ammonium ion dominating at low to medium pH, but the toxic form increasing as
pH increases, and accounting for 46–55% of measured ammonium at pH > 9.5
(DWAF 1996).
Changes or interference in any of the above chemical processes may have
implications for nutrient availability, the availability of toxins to biological
organisms and the chemical nature of different waters.
ƒ Biological processes: These include primary production or photosynthesis (which
in turn has effects on chemical processes, since it affects oxygen concentrations in
the water, as well as pH) and decomposition processes (this involves the aerobic
(with oxygen) or anaerobic (without oxygen) breakdown of organic material. For
example, the stable end-product of ammonia break-down is a nitrate salt. Certain
biotic interactions (e.g. feeding, pollination, competition, and parasitism) can all
affect the functioning and structure of an aquatic ecosystem. These factors in turn
vary naturally as a result of variations in physical factors (such as light and
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temperature), chemical factors (such as nutrient concentrations, which may
encourage or discourage the growth of certain plants, with implications for primary
production rates, decomposition, grazing rates etc.) and by interactions between or
among particular species.
Changes or interference in any of the above biological processes may have
implications for the biodiversity of aquatic ecosystems, natural resources, the rate
and effectiveness of water cleansing and the recreational and aesthetic properties
of the ecosystem (e.g. growth of unsightly reeds or pest plants that are toxic or
block waterways).
2.3.2 How do these processes apply at the level of different rivers?
All of the processes described in the previous section (Section 2.3.1) vary both
between different types of rivers (e.g. between seasonal or ephemeral rivers, and
perennial rivers) and within the course of a particular river. A river can be divided
into different sections (referred to as reaches), based mainly on the gradient of the
river bed in that particular reach. Broadly, the categories comprise:
ƒ the headwaters, or upper, source area of a river
ƒ the mountain stream reach
ƒ the foothill reaches
ƒ the lower reaches
ƒ the estuary
Each of these reaches is characterised by particular chemical, physical and biological
conditions. It is a mistake to think of these reaches as being separate ecosystems,
however. A vitally important aspect of river management is the idea of a river being
a continuum from its source to the sea. The continuum is however made up of
different communities, which are adapted to the specific conditions in which they
occur within the river. Many riverine organisms depend on processes occurring
further upstream - such as the quantity and type of food that becomes available to
them. For example, upstream organisms may process large leaves in the upper
reaches. Remnant small particles drift downstream, providing food for a range of
different animals, with adaptations that allow them to collect fine particles
effectively.
The processes and features of upstream reaches thus influence those in reaches
further downstream, and impacts in one reach can have effects that extend all the
way downstream. By the same token, however, the fact that rivers function as
continua also means that rivers can recover from impacts. Organisms that are lost
from one section of a river may re-colonise that section, from upstream, unimpacted
areas.
Figure 1 provides an overview of the way in which the different processes described
above change with distance downstream, using a theoretical river as an example.
Not all rivers have all the reaches that are described in the figure, and there are
many variations between different kinds of rivers (e.g. in the fynbos, the headwaters
of many streams are not covered over by a canopy of trees).
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8
Figure 1
Schematic diagram of a theoretical river, showing main physical, chemical and biological
characteristics of different reaches
Environmental Engineering – Sustainable Development in Coastal Areas
Module 3 Water: Core Notes for Water Quality Lecture
2.3.3 What happens at a catchment level?
Definition: A catchment is all the land between the mountains and the sea that is drained by
one river system.
The physical, chemical and biological characteristics of any river are determined
almost entirely by the nature of the catchment the activities, human and natural,
that take place in it (Davies and Day 1998). It follows then that rivers will reflect the
“health” of their catchments. Responsible catchment management will result in
healthy, functioning riverine ecosystems that are able to provide the range of
services valued by human as well as natural communities. By contrast, irresponsible
or uninformed catchment management will result in rivers that are unable to function
naturally. These rivers are often beset by a wide range of problems, that range from
poor water quality (this has human health implications).
Box 3: The benefits of conserving indigenous riparian fringes for catchment
management
Riparian fringes provide:
ƒ refugia (places of refuge) for many terrestrial animals, particularly where the surrounding
habitats have been impacted;
ƒ corridors, linking islands of residual habitat in the catchment;
ƒ buffer areas between sources of pollution and the river;
ƒ stabilisation of river banks, and so prevent erosion;
ƒ other wetland functions (see Section 3.2).
2.3.4 How do ecosystem processes apply at the level of different
wetland types?
Like rivers, wetlands also have different hydrological, biological and chemical
regimes, all of which affect their functioning and composition. Many wetlands, for
example, are naturally seasonal. They may be wetted for anything from a few weeks
to a few months each year (and some are not even wetted on an annual basis). Box
4 provides an example of such seasonal wetlands, and how increases in flow can be
as harmful to natural ecosystems as decreases in flow and other more obvious
impacts.
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Box 4: The temporary wetlands of the south western Cape
In terms of their function, structure, and the species of animals and plants that they support,
the temporary water bodies of the southwestern Cape can be regarded as unique, with biota
that are adapted to a cycle of changing physical and chemical conditions, depending on the
time of year. This element of cyclicity is vital to the continued natural functioning of these
ephemeral systems, and their drying out, often after only a few weeks of inundation, plays an
important role in defining them as unique habitats, inhabited by highly adapted organisms.
Such ephemeral pans were once common in the south-western Cape, but the onslaught of
housing, road, industrial and agricultural developments has led to their being reduced to only
a few isolated systems. Furthermore, nutrient-enriched water and an elevated water table
(Grindley 1982; Langley 1989 in Hall 1990) are believed to have changed the integral
functioning of many of those wetlands that do remain, and have resulted in a wide-scale loss
of habitat diversity, and the creation instead of large, monospecific (dominated by a single
species) stands of bulrush.
3
Water quality in South Africa
3.1 What is water quality?
Water quality is defined as “the combined effect of the physical attributes and
chemical constituents of a sample of water on a particular user”.
Physical attributes would include factors such as temperature, gradient and flow rate,
while chemical attributes would include concentrations of O2 and various dissolved
ions (e.g. nitrates, nitrites, ammonium), pH . Legally recognised “users” of water
resources in South Africa are:
ƒ industry
ƒ drinking water
ƒ transport and
ƒ the natural environment.
It should be noted that water quality is perceived as “good” or “bad” only in terms of
the requirements of a particular user. For example, unimpacted water from a saline
lake would be perceived as of “poor” quality from the perspective of a human
requiring drinking or irrigation water. However, it would probably be of “good”
quality to a brine shrimp that survives only in saline waters.
3.2 What happens when water quality changes - and does it
matter?
Changes in water quality may result in:
ƒ Shifts in the physical position of a community of riverine organisms (e.g. if the
upper reaches of a river become turbid and nutrient-enriched, one might find that
riverine communities resembled those occurring in the lower (turbid and nutrient-
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enriched) reaches of the river more closely than those naturally associated with the
upper reaches)
ƒ the introduction or the loss of key (sometimes nuisance) species (snails, blackflies,
excessive plant growth )
ƒ Reduction in diversity as a result of increased concentrations of toxins etc.
ƒ Reduced ecosystem functioning
These potential changes mean that impacts that affect water quality can have
potentially devastating ecological, social and economic implications.
3.3 Natural water quality
Knowing natural water quality allows river managers to predict the effect of changes
in water quality on a system and to find out how close existing water quality
conditions are to the natural condition.
There is however an enormous diversity of rivers and wetlands. Different kinds of
systems function in very different ways, support different biotas and respond in
different ways to perturbations. A number of factors contribute to natural variations
in surface water quality. These are:
ƒ Climate: temperature influences the rate of evaporation; precipitation affects the
amount of water falling to the ground; both these factors influence the
concentrations of different components in surface water
ƒ Geomorphology: the “structure or shape of a river bed, for example, influences the
velocity of runoff and the amount or perturbation of the water. These factors in turn
can influence water oxygenation; temperature; erosion power and concentrations
of suspended solids in the water column
ƒ Geology: the underlying rock formations influence water quality. For example,
waters passing through areas dominated by Malmesbury shales tend to have higher
concentrations of dissolved salts, leached from the ancient marine sediments that
comprise the shales, than do waters flowing through the very old, weathered Table
Mountain sandstones.
ƒ Biota: different communities of plants and animals can also affect water quality –
e.g. plants high in humic acids in the fynbos biome result in runoff from these areas
that tends to be highly acidic.
Figure 2 shows the natural variation surface water chemistry across South Africa as a
result of a combination of the above factors. The regional differences in water
quality can be divided into two broad areas as follows:
ƒ the south and east of the country, where relatively equitable climates result in
mainly perennial rivers, with relatively “pure” water (i.e. water low in total
dissolved solids)
ƒ the arid interior, where rivers tend to be seasonal or ephemeral (except for the
Orange River, the headwaters of which are in the east of the country); waters tend
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to be high in concentrations of total dissolved solids, largely as a result of
evaporative concentration during hot, dry periods.
Figure 2
Map of South Africa showing the distribution of chemically distinct
types of ground water (after Davies and Day 1987, adapted from
Bond 1946)
3.4 What causes changes in water quality?
3.4.1 Changes in water quantity
Changes in water quantity (including changes in the magnitude, duration and/or
frequency of flows) can affect processes such as flushing of sediment and algal
material (this would have implications for concentrations of suspended solids, as well
as rates of nutrient uptake, oxygenation (as a result of photosynthesis) and general
concentrations of dissolved material (e.g. pollutants entering a river will be more
concentrated (and thus potentially more damaging) where flows have decreased.
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Box 5: Other reasons why altering natural flow patterns in a river matters
River and wetland ecosystems are dependent on particular flow regimes. When these flows
change, as they do naturally, it takes time for the riverine community structure to adjust to
the new regime. If, however, there is no pattern to the flow regime, and the river flows
sporadically after effluent releases, then lies dry, then flows again, the natural cues to which
species respond, such as combinations of light, temperature, water flow and water quality, are
thrown into disarray, and only very hardy, if any, communities are likely to be able to survive
in such a system.
3.4.2 Changes in river morphology
Among the most common impacts to river morphology are canalisation (passing of
river water through concrete or otherwise hardened, stabilised surfaces) and
channelisation (passage of river water along earth furrows).
Canalisation is one of the most common states of urban rivers. In the past, it was
often instituted to speed up water flows and allow encroachment into floodplains
without risk of flooding. It can however result in near-total loss of natural ecosystem
functioning in a river, with ecologically devastating impacts that include (after Davies
and Day 1998):
ƒ the creation of a homogeneous environment, which offers no protection to aquatic
organisms from scouring floods, and provides no habitat diversity, to enable a wide
range of organisms to inhabit the system. Thus few organisms inhabit canals and
plant growth, other than algae, is usually non-existent.
ƒ depriving the river, through the loss of particular aquatic organisms, of the “selfcleansing” function that is a feature of natural rivers, whereby aquatic communities
process organic matter and maintain the system in a healthy condition
ƒ a loss of connectivity between the river and the flood plain caused by the concrete
walls of the canal. This impacts on wetland and riverine plants that would naturally
be associated with the damp conditions prevalent on the flood plain.
ƒ allowing the encroachment of urban developments right up to the edge of the canal
wall. This factor severely limits the scope for future rehabilitation of many river
channels.
Channelisation is frequently the result of dredging, to remove sediment or aquatic
vegetation and so improve passage of water through a river during floods.
But channelisation results in:
ƒ steepening of banks, making it difficult for river-associated animals to gain access
to the river;
ƒ altering of fringe habitats;
ƒ destabilisation of river banks, often followed by undercutting and erosion;
ƒ loss of marginal and bankside vegetation – an important habitat for aquatic, semiaquatic and river-associated fauna;
ƒ drainage of riverine wetlands, by lowering the depth of the river bed;
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ƒ increasing separation of the river from its floodplain and loss of annual flooding of
floodplains and associated wetlands.
3.4.3 Pollution
Pollution can be defined as the degradation of natural systems by the addition of
harmful substances. It is discussed in more detail in Section 4.
4
Pollution1
4.1 Types of pollution
Pollution can be classified on the basis of the type of pollutant or the source of
pollution, and also according to the resource that is impacted upon that is, air
pollution, water (freshwater, groundwater and the sea) pollution, or soil pollution.
This section deals mainly with water pollution, although it is noted that both ground
and air pollution may result in pollution of surface and or groundwater.
4.1.1 Pollution categorised by Source
Pollution-causing substances, such as pesticides and other persistent toxic organic
compounds, heavy metals, radioactivity, human and animal effluent, and toxic
gases, originate mainly from waste. Waste, the unwanted but unavoidable solid,
liquid or gaseous by-products of all human activities, could originate from a wide
range of human operations, such as households, industry, commerce, transport,
agriculture, medicine, etc. The production of waste is characteristic of humankind
living in an modern society, and the more advanced the level of civilisation, the
greater the production of waste. Furthermore, indications from available data show
that the amount and hazardous nature of waste generated is in almost direct relation
to the growth of the economy. The management of waste, and especially its
disposal, is therefore a growing problem, since waste may contain substances that, if
not effectively controlled, can be harmful to humans and the environment. Several
factors determine the hazard posed by the presence of substances in the
environment, including:
ƒ the origin of the substances concerned (for example, domestic, industrial,
commercial, medical, construction, nuclear, agricultural);
ƒ chemical properties (for example, inert, toxic, inflammable);
ƒ physical properties (for example % moisture content);
ƒ composition (for example ionising radiation, noise pollution, and excessive heat);
ƒ quantity (volume);
ƒ reactivity (flammability, explosion);
ƒ biological and ecological effects (toxicity and concentration);
1
Note that Sections 4.1 and 4.2 have been extracted from DWAF (2001) with only minor alteration.
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ƒ mobility (potential to be transported in the various environmental media);
ƒ persistence (accumulation);
ƒ indirect health effects (pathogens and vectors); as well as pathways of transport
and exposure.
Some wastes may be recycled, some incinerated, some treated and concentrated,
but eventually some residue remains which is transferred to the environment.
Wastes with a high moisture content are usually treated and piped into a water
resource (effluent discharge), but are often also disposed of on land (solid waste
disposal), sometimes along with wastes of lower moisture content (co-disposal),
while gaseous wastes are mostly vented into the atmosphere (emission). When
waste is “disposed” on land, it is in fact merely being “stored” in a facility that is
hopefully able to mitigate against the risks posed by such “storage”, and when
effluent is “discharged” into a water resource, it is not gone forever; it is merely
transported to a different location, where it is assimilated by the natural system, or
may settle out, or be removed so that the water can be reused. Without suitable
management, waste emission, discharge or disposal lead to adverse health
conditions and has the potential to lead to irreversible deterioration or damage of the
environment at large.
4.1.2 General impacts of pollution on the Receiving Environment
(Resource)
Pollution is of concern for human and environmental health as a result of discharges
to water, air, and the terrestrial environment (land). However, transfers can occur in
both directions between the atmosphere, water, and the land, with consequences for
both the spread of pollution and its effects. For example, the emission of sulphur
dioxide—caused by the combustion of fossil fuels such as gas, petroleum, and coal—
into the air can result in the acidification of soils and lakes when it reaches the
Earth’s surface. The recognition of the integrated nature of the environment,
especially the hydrological cycle and the interrelationships between surface water,
ground water and atmospheric water, evolved only in the past fifty years. It has
been shown throughout the world that the discharge of water containing waste
(effluents) into surface water resources has lead to the deterioration of these
resources. Waste disposal on land can result in soil, water and air pollution, although
the most severe impact is ultimately on the water resource, since such disposal is a
major contributor to the degradation of aquifers.
4.1.3 Specific impacts of pollution on ground and surface water
Water pollution is the degradation of water quality as measured by biological,
physical or chemical criteria, and this degradation is generally judged in terms of the
intended use of the water, its departure from the norm, its effects on public health,
or ecological impacts. If the intended use is, for example, recreation or eco-tourism,
any deviation from natural background levels (norm) may well be deemed pollution.
The removal of pollutants from water resources for the human and economic use of
such water obviously has a cost implication, and the higher the level of impurity, the
more expensive the treatment of the water for re-use. Certain resources, for
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example wetlands and groundwater, are also more vulnerable to the effects of
pollution than other types of water resources.
Pollutants can enter the water environment from both point and non-point sources.
Point sources are discreet and defined, such as pipes of canals emptying into
(mainly) surface water bodies from municipal or industrial sites. In general, the
control of point sources before discharge, through on-site treatment, is easier than
the control of non-point sources. Non-point sources are diffuse and intermittent,
influenced by factors such as land use, climate, hydrology, vegetation and geology,
and are difficult to control. Non-point sources result from the intentional or
unintentional disposal or discharge of waste on land, and include poorly managed
waste disposal sites, and urban and industrial runoff from streets or fields, which
may contain all types of pollutants, from heavy metals to sediment. Rural sources of
non-point pollution are generally associated with mining, agriculture or forestry.
Non-point sources can impact on both the surface and groundwater component of
the water resource. Of the two categories of pollutants, point source pollutants are
usually much easier to control and identify.
Surface water pollution arises from the discharge of industrial, agricultural, and
human wastes into freshwaters, estuaries, and seas. This may result in the poisoning
of aquatic organisms or the depletion of oxygen owing to excessive growth of microorganisms (anthropogenic eutrophication), which makes less of the water habitable
for fish, and diminishes the carrying capacity of the resource.
Of particular importance in the consideration of pollution problems in any component
of the water resource, are the reservoir sizes and residence times of water in the
various parts of the cycle.
Reservoir size of surface water bodies is of particular importance when determining
carrying or “assimilative” capacity, as well as for ground water when determining
potential importance for use. Water in rivers has a relatively short residence time
(usually measured in weeks), whereas water in ground water bodies has a residence
time that can run into hundreds or even thousands of years. Therefore, a solitary
pollution incident affecting a river (such as a spill from a rural sewerage works) will
have a short-lived impact because the water will soon leave the river environment
(provided that the incident does not involve the
adsorption of pollutants onto sediment on the river bed, which would result in a
much longer residence time). Pollution problems are more likely to result from
chronic processes which discharge pollutants directly into rivers or onto land over an
extended period of time (Keller, 1992:245). Due to the fact that the residence time
of groundwater is so long, natural removal of pollutants from ground water is a
slow process, and abatement is extremely difficult and costly.
Little is known about the health effects of the proliferation and variety of unidentified
and potentially hazardous, if not toxic, chemicals that enter the water supply from
sources such as effluent treatment plants, sewerage works, etc. when they are not
effectively removed at these facilities. Where freshwater resources are limited, as in
South Africa, a greater supply of water may be drawn from rivers and ground water
that may be polluted from a range of toxic or hazardous substances from domestic,
industrial and agricultural wastewater sources. Examples include nitrates from
agricultural practices and septic tank sewer systems, tri-halomethanes from the
chlorination of water with a high organic content and, the latest scare, oestrogensimulators from sewerage treatment works.
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The rest of this section outlines (in brief) some of the main forms of pollution that
are likely to affect aquatic ecosystems. They have been grouped in terms of
inorganic and organic pollution types.
A
Inorganic Pollution
Heavy metals
The following paragraphs summarise some of the effects and interactions of a
number of heavy metals on aquatic ecosystems in general. These effects have been
divided by DWAF (1996) into three graded levels for South African aquatic
ecosystems as a whole, namely:
ƒ target water quality range (TWQR) – the range of concentrations or levels within
which no measurable adverse effects are expected on the health of aquatic
ecosystems;
ƒ chronic effect values (CEV) – the concentration or level of a constituent at which
there is expected to be a significant probability of measurable chronic effects to
certain species in the aquatic community;
ƒ acute effect value (AEV) – the concentration or level of a constituent above which
there is expected to be a significant probability of acute toxic effects on certain
species within the aquatic community. If such acute effects persist for even a short
while, or occur at too high a frequency, they can quickly cause the death and
disappearance of sensitive species or communities from aquatic ecosystems.
ƒ Aluminium: this is a naturally abundant element. It is relatively insoluble in the
neutral pH range (pH 6-8). However, at pH >8.0 (alkaline conditions) or pH < 6.0
(acidic conditions), higher concentrations may be mobilised. Under acidic
conditions, aluminium is present in a soluble, toxic form, that is available to living
organisms. Under alkaline conditions, aluminium is present as soluble, but
biologically unavailable complexes (DWAF 1996). At low pH, however, aluminium
may also form complexes with ions and a number of different organic materials,
including the humic substances commonly found in blackwater fynbos systems.
ƒ Copper: dissolved copper is extremely toxic in water, even at low concentrations.
The effect of elevated copper concentrations on aquatic organisms is related to
factors such as the duration of exposure, and the life stage of the organism, with
early life stages (e.g. eggs and larvae) being apparently more sensitive than adults.
Elevated copper concentrations are associated with changes in species richness and
community composition in aquatic ecosystems (DWAF 1996).
The toxicity of copper varies with water hardness, with similar concentrations of
dissolved copper being more toxic in soft water than in hard water.
ƒ Lead: Lead is considered potentially hazardous to most forms of life. It is toxic and
relatively accessible to aquatic organisms and, in freshwater ecosystems,
accumulates readily in the living tissue of plants, invertebrates, fish and bacteria.
Lead becomes increasingly available to organisms as pH decreases. Soluble lead is
however removed from solution by association with sediments and suspended
particles of inorganic and organic material. Hardness of water (measured in terms
of concentrations of calcium) is an important factor in determining the toxic effects
of lead in aquatic environments, and lead is potentially more toxic in soft than in
hard waters.
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B
Organic Pollution
Nutrients
These include:
ƒ Phosphorus: In natural freshwater conditions, phosphorus concentrations are
often growth-limiting, and the most significant ecological effect of elevated
phosphorus concentrations is its stimulation of aquatic plant growth. However, not
all forms of phosphorus are available for uptake by plants, and factors such as
light, temperature and the availability of other nutrients also play important roles in
determining plant growth. The following terms from DWAF (1996) are used to
define and describe the effects of broad ranges of phosphorus concentrations in
aquatic ecosystems:
< 0.005 mg p/l:: oligotrophic conditions; that is, low levels of species diversity;
low productivity systems with rapid nutrient cycling; no nuisance growth of
aquatic plants, no presence of problem algae;
0.005-0.025 mg p/l: mesotrophic conditions – that is, high levels of species
diversity; usually productive systems; nuisance growth of aquatic plants and
blooms of blue-green algae; algal blooms seldom toxic;
0.025-0.250 mg p/l: eutrophic conditions – that is, usually low levels of species
diversity; usually highly productive systems; nuisance growth of aquatic
plants and blooms of blue-green algae; algal blooms may include species
that are toxic to humans, livestock and wildlife;
>0.250 mg p/l: hypertrophic conditions - that is, usually low levels of species
diversity, highly productive systems; nuisance growth of aquatic plants and
blooms of blue-green algae; algal blooms may include species that are toxic
to humans, livestock and wildlife.
ƒ Nitrates: Nitrates are the end products of aerobic stabilisation of organic nitrogen.
ƒ Nitrites: Nitrites are an intermediate stage in the conversion of ammonia to
nitrate, and occur naturally in fresh and saline water.
ƒ Ammonia: Ammonia is a common pollutant in sewage and industrial effluents; it
exists in a free, un-ionised form (NH3), which is toxic, and an ionised form (NH4+),
which is not toxic. The concentration of the toxic form varies with pH and
temperature – at low to medium pH, NH4+ dominates; as pH increases, toxic NH3
increases. Ammonia affects the respiratory systems of many animals.
The overall effects of nitrogen on aquatic ecosystems can be summarised as
follows, based on average summer inorganic nitrogen concentrations:
<0.5 mg n /l: oligotrophic conditions - that is, low levels of species diversity; low
productivity systems with rapid nutrient cycling; no nuisance growth of
aquatic plants, no presence of problem algae;
0.5-2.5 mg n/l: mesotrophic conditions – that is, high levels of species diversity;
usually productive systems; nuisance growth of aquatic plants and blooms of
blue-green algae; algal blooms seldom toxic;
2.5 – 10 mg n/l: eutrophic conditions – that is, usually low levels of species
diversity; usually highly productive systems; nuisance growth of aquatic
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plants and blooms of blue-green algae; algal blooms may include species that
are toxic to humans, livestock and wildlife;
>10 mg/l: hypertrophic conditions – that is, usually low levels of species diversity,
highly productive systems; nuisance growth of aquatic plants and blooms of
blue-green algae; algal blooms may include species that are toxic to humans,
livestock and wildlife.
Other indicators of organic pollution include the presence of faecal coliform bacteria
(Escherichia coli), and low concentrations of dissolved oxygen in the water (often the
result of rapid decomposition of organic material)
Note that organic pollution in itself is usually harmless. However, in high
concentrations, it encourages the growth of algae (including nuisance and toxic
algae, as well as habitat-altering filamentous algae), and hence increases in
decomposer microbes. Rapid decomposition of organic material may lead to
anaerobic conditions.
Examples of organic polluters include:
ƒ some industrial effluent (including food industry)
ƒ waste water treatment plants (e.g. sewage and stormwater)
ƒ raw sewage may also contain harmful organisms such as roundworm
C
Other Pollutants
Suspended Solids
Unnaturally high concentrations of sediment suspended in a water body (measured
as Total Suspended Solids – a gauge of turbidity) may be associated with the
following impacts: reduction in light penetration through the water, leading to a
decrease in photosynthesis (particularly important in the case of deep waters,
possibly less important in the case of shallow systems). Changes in photosynthetic
rate may affect food availability for aquatic organisms higher up the food chain.
Suspended solids may also interfere with the feeding and breathing mechanisms of
certain aquatic organisms, including fish, tadpoles and many invertebrate species.
Settling out of suspended material may result in smothering of plants and bottomdwelling animals.
pH
pH is a measure of the activity of hydrogen ions in a water sample. Surface waters
exhibit a range in pH between 4 and 11. In the fynbos bioregion, pH may drop to as
low as 3.9, owing to the influence of organic acids, such as humic and fulvic acids.
Diurnal and seasonal variations in pH are also common, due to differences in
photosynthetic and respiration rates, which affect the concentrations of CO2 in the
water.
Changes in pH can affect the ionic and osmotic balance of aquatic organisms, the
availability and toxicity of certain trace metals, non-metallic ions such as ammonium
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and certain other elements. Metals that are particularly affected by changes in pH
are silver, aluminium, cadmium, cobalt, copper, mercury, manganese, nickel, lead
and zinc. All of these become increasingly biological available or soluble at lowered
pH. Changes in pH also affect the rate at which large organic molecules are able to
adsorb trace metals and other materials.
Examples of “acid producing industries” include the chemical, pulp and paper, mining
industries.
4.1.4 Assessing the risks of pollution
Almost all human activities result in the production of some substance and all
chemical substances can be considered as potential pollutants of the environment.
While environmental pollution must be prevented, it would be virtually impossible to
reduce all environmental exposure to contaminants.
One of the first principles for action of the Brundtland Commission is that: “decisions
should be based on the best possible scientific information and analysis of risks”.
The hazards posed by some waste types are obviously dangerous due to their
inherent physical or chemical characteristics, and will have a harmful effect on
humans upon exposure, such as death or disease. Other wastes may appear
“harmless” or “non-hazardous”, but become a cause for concern as a result of the
effects of chronic exposure or when they decompose, or due to the fact that they are
disposed of in a particularly sensitive environment (for example the disposal of ash
in a wetland). It is typically the second group of wastes that are often
accommodated in the environment, with or without pre-treatment, and that can
cause pollution problems as a result of such accommodation in an unsustainable
manner. Although the popular concern is focused on those chemicals that will cause
ill effects to humans in small doses (known as “toxic chemicals”), the effects of other
substances, which are not necessarily harmful to humans, must also be considered,
since they could pose a hazard to some component of the environment. In some
instances the cumulative effect from these substances may pose an even greater
long-term risk than the risk posed by small quantities of “toxic” chemicals.
4.2
Pollution as a result of dense settlements2
4.2.1 Water quality problems in dense settlements
A number of water quality problems are associated with dense settlements. The most
important of these are:
ƒ Microbiological contamination by faecal pathogens, which has severe health
implications for water users and the community. These mostly come from human
excreta, and dirty washing water (grey water). However, high concentrations of
faecal bacteria may be found in stormwater runoff, and in livestock faeces.
ƒ Nutrients, mainly phosphorus and nitrogen, which cause eutrophication and
increase the costs of treating water to potable standards. These mostly come from
2
This section has been extracted with only minor changes from DWAF 2000
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human excreta and grey water, but may also be present in high concentrations in
the stormwater runoff.
ƒ Solid waste (litter) from public spaces and from household refuse, which causes
ecological, aesthetic and health problems, and affects the functioning of stormwater
and sewage services.
ƒ Sediment from unpaved areas in the settlement, which accumulates in rivers and
dams, affects aquatic habitats, and reduces storage of stormwater run-off.
ƒ Habitat destruction mostly by building in the riparian zone which affects the natural
functioning of river ecosystems, and allows waste to get into the rivers.
(Other wastes, such as oxygen demanding substances, metals, hazardous wastes
and salts may also be associated with settlements, but are considered less important
in the South African context.)
4.2.2 Four waste streams
The above wastes are associated with four waste streams: ƒ sewage waste (human faecal matter),
ƒ grey (or sullage) water,
ƒ stormwater and runoff from the settlement, and
ƒ solid wastes (mostly household refuse and litter).
These waste streams interact, e.g. faecal matter from blocked sewers or litter may
be washed into the water resource by stormwater runoff, while solid wastes may
block sewer systems. Management of the water quality impacts of dense settlements
must, therefore, be aimed at all of these waste streams.
4.2.3 Physical, Institutional and Social causes of pollution in dense
settlments
Water quality problems result from the physical breakdown or inadequacy of one or
more of the waste streams and are mostly associated with inadequate, or poorly
functioning, services. These physical causes of water quality problems include
inappropriate sanitation for the density of the settlement, no facilities to dispose of
grey water, sewer blockages due to inappropriate design, and poor design of solid
waste removal services. Encroachment onto, and destruction of the riparian zone,
also impacts on the water environment can be considered as a physical problem.
However, these physical causes of pollution are situated within the social and
institutional environment within the settlement. These exacerbate or directly cause
the physical problems. Important institutional concerns are a lack of funds within
the Local Authority to address the problems, a lack of capacity to maintain the
services, and the diversion of resources to other priorities. Social issues include nonpayment or illegal use of services, vandalism and a lack of awareness with respect to
the proper use of the services.
Pollution in settlements must be managed by addressing all three of these
components. This requires addressing the physical factors which contribute to the
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problem, usually by direct intervention within one of the four waste streams, as well
as the underlying institutional and social issues, usually by softer intervention
options like capacity building and education.
The water quality effects of settlements must be managed by addressing
the physical problems associated with the four waste streams, but the
sustainability of these physical interventions rests on addressing the
institutional, and social factors contributing to the problem
4.2.4 The Production, Delivery, Transport and Use continuum
Pollution from dense settlements, and its effects on water users, can be divided into
four processes. These elements represent a conceptual continuum, which describes
the pathway pollutants may follow from the point at which they are generated to the
point at which they impact on the use of the water. The elements are:ƒ Production refers to the generation of waste within the settlement. This includes
waste generated as human excreta, as solid waste (litter), as sullage or grey water,
as livestock wastes, from cultivated areas, from vehicles and from atmospheric
deposition. Minimising the production of waste equates to a philosophy of waste
prevention.
ƒ Delivery refers to the movement of these wastes into the surface or groundwater
environment. This occurs from the breakdown of the sewerage system, stormwater
runoff, direct disposal to the rivers, or as seepage into the groundwater. Minimising
the amount of waste left behind in the settlement (i.e. that which can be delivered
to the water environment) ensures waste minimisation, and usually relates to the
level and operation of services. Similarly, management practices aimed at trapping
this waste before it is delivered to the water environment ensure impact
minimisation.
ƒ Transport refers to the movement of waste once it has reached the water
environment, as well as the chemical, physical and biological transformations that
may occur in this process. Transport occurs through either the surface or
groundwater component.
ƒ Use refers to the action of using the water. This also provides opportunities for
management, for example by treating the water before use, or by warning
communities not to use, or swim in, rivers and dams. (Figure 3.2)
While the problem of water quality can be addressed at any point in this continuum,
this Strategy focuses on management of waste before it reaches the water
environment i.e. on the Production and Delivery elements. However, in emergency
situations, like cholera outbreaks, management of the Transport and Use
components should be considered.
4.2.5 Waste production in Settlements
The amount of waste produced in any settlement is primarily associated with its size
and density. The larger the settlement, the more waste is produced. The more
densely populated the settlement, the more waste which is produced in a smaller
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area. In very dense settlements, lack of space also forces people onto the riparian
zone, which contributes to the settlement’s impact on the water resource.
However, a number of other issues influence the amount of waste produced. The
socio-economic status of the settlement determines the amount of waste produced
per household. Poorer communities produce less waste per household, while
settlements provided with in-house water supplies tend to produce more grey water,
or wastewater (i.e. when communities are supplied with a fully reticulated sewerage
system). Waste production from agricultural activities, like livestock or small
agricultural fields can also be a problem in rural communities.
Effective planning, servicing, and siting of settlements can pro-actively manage the
amount of waste produced by settlements. This involves selecting appropriate
housing densities and services for the receiving water environment class, or the
siting of settlements that may result in water quality problems away from sensitive
water resources. Where settlements are planned along river courses, planning to
ensure protection of the riparian zone can also be construed as waste prevention
(although destruction of habitat does not produce waste per se). This may include
siting sports fields or other recreational facilities along rivers to prevent
encroachment into the riparian zone.
However, waste production can also be managed reactively by focusing on the social
factors which promote waste production, for example by encouraging behaviour like
recycling and fertiliser production from composting toilets. Water saving schemes
which reduce the volume of sullage water are also particularly suited to settlements
with a higher water use, and may reduce the load on the waste water treatment
plant. Similarly, regulating livestock numbers can contribute to minimising the
amount of waste produced. It is, however, inappropriate to restrict socio-economic
development in order to effect waste prevention.
4.2.6 Waste delivery in settlements
The amount of waste delivered to the water environment is primarily associated with
inadequate or poorly functioning services. The levels and operation of services in the
settlement determine how much waste is left behind in the settlement. Waste that is
left behind in the settlement can potentially be delivered to the water resource. For
example, pit latrines leave the sewage waste in the settlement, and nitrate may seep
into the groundwater. Similarly skip systems for household refuse often overflow and
leave solid waste behind in the settlement, which can be carried into the water
environment by stormwater or wind.
In sparse settlements natural assimilation of waste in the delivery pathway, means
that little waste will actually reach the water resource. But, as settlement densities
increase, the amount of waste produced increases, and fewer open spaces provide
less opportunity for the natural assimilation of the waste during delivery. Well
operated services which ensure safe disposal of the waste are, therefore, more
important as settlement densities increase. Reducing the amount of waste that can
be delivered to the water resource by ensuring services that are appropriate for the
size and density of the settlement promotes waste minimisation in settlements.
Similarly, management practices that trap and remove waste in the delivery
pathway, for example litter traps or stormwater detention ponds, also ensure
delivery management.
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Waste minimisation in settlements may also be pro-active by intervention in the
planning of services for settlements, or may be reactive by upgrading services in
settlements with inadequate services, or by ensuring the appropriate use and
maintenance of the services. Inappropriate use or maintenance of services has been
identified as one of the most serious issues associated with the more dense urban
and peri-urban settlements in South Africa. Higher levels of service must, therefore,
be associated with better maintenance of the services. This requires capacity building
and training with respect to these services, and advocates the use of low
maintenance, intermediate levels of service where ever possible.
4.2.7 The pollution cycle
Much of the problem of pollution of dense settlements occurs when the levels and
operation of services are inappropriate for the amount of waste produced in the
settlement. The amount of waste produced in settlements is, in most cases,
associated with the density of the settlement. These settlements usually house the
poorer communities. Service providers are often hesitant to supply these poor
communities with high levels of service, as they are unlikely to be able to pay for
these services. Where high levels of service have been supplied, a lack of funds to
maintain these services often leads to the breakdown of these services. This is
exacerbated by a lack of understanding within poorer communities of the operation
of the services, a culture of non- payment, or even the deliberate vandalism of the
services.
In these communities a polluted environment demoralises the community and
encourages further pollution, or limits the effectiveness of those services which are
provided, e.g. where litter blocks stormwater systems, or where overflowing skips
prevent people from safely disposing of household refuse. Where large amounts of
waste are left in the settlement, the community is less likely to take care when
disposing of waste, to pay for services, and to report breakdowns in service
provision. This leads to further pollution, eventually leading to serious health effects
for the community. This forms a pollution cycle, which tends to exacerbate the
problems over time
The key to the sustainable management of pollution from settlements lies in
breaking this pollution cycle. This requires both services to manage the waste, and
capacity building within the service providers and community in order to build an
awareness of the need to maintain these services. Education of the community with
respect to the need to pay (or at least part pay) for these services is also critical.
However, it is unreasonable to expect people to pay for higher levels of services if
litter is lying knee deep in the streets and vice versa. This requires better
relationships between service providers and consumers where consumers demand
effective services in return for payment.
4.3 Balancing services and affordability
Government agencies in all three spheres of government have been actively
developing policies, strategies and minimum standards with respect to the delivery of
services, housing, land tenure and land restoration. These strategies have all been
constrained by economic realities, and by the lack of resources to implement even
the best intentions of these agencies. Minimum standards have been set at levels
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that are considered to provide the basic levels of service to alleviate the plight of
disadvantaged communities, but which are also considered to be affordable to the
community. The services recommended generally have the advantage of low
maintenance costs, and are hence more affordable to the community. High levels of
service, which are not affordable to the community are, therefore, considered to be
unsustainable, and are often discouraged. The Government has, therefore, decided
on RDP levels of service, which consist inter alia of a Ventilated Improved Pit Latrine,
and 25L of water per person per day within 200m of the home, as the basis for
sanitation and water supply. Similarly, NaSCO has made a strong case for VIPs as a
basis for sanitation services in their Peri-urban Sanitation Policy.
In many cases the advantages of supplying these services, where no services
previously existed, are seen to far outweigh the possible environmental
consequences of these services. Many service providers also argue that these
services will realise an environmental benefit where they replace bush and spade
toileting3 or bucket toilet systems. Service providers are therefore often loath to
provide better than this basic RDP level of services. Similarly, the urgent need for
land and housing is seen to outweigh the dis-benefits of development, even near
sensitive environments. While all these agencies have included the need for
environmentally sustainable services in their policies, insistence on higher levels of
service, or the prohibition of development purely for environmental benefit, is likely
to meet resistance in many cases. More importantly, providing higher levels of
service, which are unlikely to be maintained, may create even more serious pollution
problems. It is, therefore, important to carefully weigh the need for services with
high operation and maintenance costs with the threat to the water resource.
The amount of waste that is produced in the most densely populated settlements
usually requires the highest levels of services, and the greatest attention to the
operation and maintenance of these services. However, the extent of poverty in
South Africa means that very few, if any, Local Authorities will be able to afford to
maintain high levels of services in all their settlements. This demands that in most
cases implementation of the Strategy should focus on identifying options with lower
operation and maintenance costs.
The national level pollution management strategy should ensure the following:
ƒ Management of pollution from dense settlements must be focused on the identified
waste streams, and it is important to address all of these waste steams in any
settlement.
ƒ Within these waste streams, the water quality impacts of settlements are a function
of Physical, Institutional and Social factors. All of these factors must be addressed
to ensure the sustainability of pollution management options.
ƒ The process of pollution from settlements can be divided into a conceptual
continuum of waste Production, Delivery, Transport and Use. Implementation of the
Strategy should concentrate on waste Production and Delivery, but Transport and
Use management can be considered in emergency situations.
ƒ Implementation of the Strategy should focus on breaking the pollution cycle.
3
Bush and spade toileting refers to situations where the community is forced to use open areas, often in
watercourses, for toilet facilities.
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ƒ Community participation, and in particular of women in the community is critical to
successful identification of appropriate interventions
5
Water quality standards and freshwater
ecosystems
Two sets of standards apply to the quality of water discharged into South African
rivers. The first standards are those specified under the general authorisations in
terms of Section 39 of the National Water Act, 1998 (Act No. 36 of 1998), which
apply to treated effluent that is discharged into a water body. These standards
specify both general and special limits, depending on the type of river into which the
discharge is occurring. Problems with this type of standard include, however, the
facts that:
ƒ Meeting the set standards can be prohibitively expensive for minor polluters, who
contribute very little to the total input to the system]
ƒ The standards do not take into account the total volumes of effluent released into a
river
ƒ The standards do not allow for regional differentiation.
The second set of standards are a series of target water quality guidelines,
recommended by the Department of Water Affairs and Forestry, and aimed at
minimising negative impacts of poor water quality on aquatic ecosystems in South
Africa. Target ranges for a series of different water quality constituents, including
various heavy metals, are provided in DWAF (1996). The guidelines also include
estimates of “acute effect values” and “chronic effect values”. These are defined in
DWAF (1996) as follows:
ƒ “Acute effect values: the concentration of a constituent above which there is
expected to be a significant probability of acute toxic effects to up to 5% of a
species in the aquatic community. If such effects persist for even a short while, or
occur at too high a frequency, they can quickly cause the death and disappearance
of sensitive species or communities.
ƒ “Chronic effect values: the concentration of a constituent above which there is
expected to be a significant probability of measurable chronic effects to up to 5% of
a species in the aquatic community. If such effects persist for some time, they can
lead to the eventual death of individuals and the disappearance of sensitive species
from aquatic ecosystems”.
DWAF target water quality guidelines apply to the quality of water occurring in rivers,
while the effluent standards apply to the quality of water found in the final effluent.
Note: further details on water quality guidelines and DWAF effluent limits can be found in
DWAF (2001), provided in the course reading material.
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6
References referred to in these notes
Begg, G. 1986 The Wetlands of Natal (Part 1). An overview of their extent, role and
present status. Natal Town and Regional Planning Report. Volume 68. Natal Town
and Regional Planning Commission. Pietermaritzburg.
Cowan, G.I. 1995 (ed.) Wetlands of South Africa. SA Wetlands Conservation
Programme Series. Department of Environment Affairs and Tourism. Pretoria.
Davies, B.R. & Day J.A. 1998 Vanishing Waters. University of Cape Town Press,
Cape Town.
DWAF 2001. Water Quality Management Series. Water quality management
orientation course. The bigger picture: Introduction to sustainability, environmental
management and water quality. Revision 1.
DWAF 2000 Water Quality Management Series. Water quality management
orientation course. Water quality management within a catchment context.
DWAF 2000. Water Quality Management Series. Policy Document U 1.2. Managing
the Water Quality Effects of Settlements: - The National Strategy. First Edition.
Grindley, S.A. 1982. Estuaries of the Cape. Part II. Synopses of available information
on individual systems. Report No. 16. Eerste (CSW 6). CSIR Research Report 415.
CSIR. South Africa.
Hall, D.J. 1990 The ecology and control of Typha capensis in the wetlands of the
Cape Flats, South Africa. Unpublished PhD Thesis, Freshwater Research Unit,
Zoology Department, University of Cape Town. 249 pp.
27