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 Water Pollution and your Health


The quality of a stream or river is often a good indication of the way of life within a community through which is flows. It is an indicator of the socio-economic conditions and environmental awareness and attitude of its users.  Everything that happens in a catchment area is reflected in the quality of the water that flows through it, because the results of human activity and lifestyle ultimately end up in rivers, through runoff. 


A river catchment consists of all the land, from mountain to seashore,
that is drained by a single river and its streams.


Healthy streams, wetlands and rivers support a great variety of water life.  Rain water and tumbling mountain streams contain high levels of oxygen. Much of the oxygen comes from the atmosphere through rain, tumbling water in fast-flowing streams and photosynthesis.  Nutrient substances are washed into the system, providing important growth chemicals (eg. nitrates) and sources of food (eg. rotting plants).  Water plants, in turn, photosynthesize and provide life-supporting oxygen and other food sources for water organisms that interact in a complex web of life.


All life in the water is dependent on the interaction within the river itself and in the surrounding catchment.  These processes can either maintain a healthy ecosystem or disrupt ecological processes and degrade the water supply.  Rivers and streams owe their existence to the nature of catchments and the relationship between rainfall and evaporation.  Rivers are open systems where the exchange of material and energy within the environment occurs all the time.  It is difficult to treat rivers as ecosystems because they are important pathways for the flow of energy and the circulation of nutrients across the boundaries of habitats.


An ecosystem is an area in which plants, animals, people and their surroundings interact through various relationships, eg. a pond.


Changes in water quality occur naturally along the length of a river, however, these changes may be significantly influenced by human activities.  Industries, agriculture and urban settlements produced nutrient concentrates (sewage effluent and fertilisers) and toxic substances (poisonous pollutants) which can affect water quality.




Water quality is defined as water which is safe, drinkable and appealing to all life on earth.  It should contain no chemical or radioactive substance that is harmful to the health of any life.  It should be free of disease-causing organisms and stable in terms of corrosion or scaling.  Polluted water is water that is not safe and not healthy for people and animals to drink or to wash in. Polluted water is particularly dangerous to water plants and animals. Polluted water is also particularly dangerous to people who get their water directly from a river or dam.  In South Africa the scarce fresh water is decreasing in quality because of an increase in pollution and the destruction of river catchments, caused by urbanisation, deforestation, damming of rivers, destruction of wetlands, industry, mining, agriculture, energy use, and accidental water pollution. As the human population increases, there is an increase in pollution and catchment destruction. 


Causes of Water Pollution




As more and more people move into cities and towns, a number of factors cause pollution:


·   the physical disturbance of land due to construction of houses, industries, roads, etc.;

·   chemical pollution from industries, mines, etc.;

·   inadequate sewage collection and treatment;

·   Increase in fertilizers to grow more food.  These results in an increase in nutrients (nitrates and phosphates) in the water which causes enhanced plant growth (algal blooms).  When this plant material dies and decays the bacteria uses the oxygen in the water.  This lowering of oxygen levels results in the death of other water life that needs oxygen to survive, eg. fish, etc.  This process is called eutrophication; litter, which causes disease and has a negative visual impact.




Clearing land for agriculture and urban growth often leads to water pollution.  When soil is stripped of its protective vegetation it becomes prone to soil erosion.  This leads to an increase in the murkiness of the water which can cause the following:



·   it can block the gills of fish;

·   bottom dwelling plants cannot photosynthesize as the suns rays cannot reach them; and

·   there is an increase in disease as bacteria and viruses use the soil particles as a method of transportation.


Damming of rivers


Damming of rivers can have an impact on water in the following ways:


·   Water flowing out of dams: 

·   has reduced suspended material as a large amount settles to the bottom of dams;   is depleted of nutrients; and  is often more saline with detrimental effects on downstream agriculture and fisheries. 


·   Enhanced eutrophication may result due to the water spending a longer time in the dam. 


·   There is also increased evaporation in dams, especially those with a large surface area, such as the Vaal Dam.



Destruction of Wetlands


Wetlands are natures way of cleaning water as well as damming water (they hold back water in summer and release it in winter).  Destruction of wetlands:


·    Destroys the habitat of many birds and fish;

·    Removes the natural filters capable of storing and degrading many pollutants, such as phosphorus and heavy metals;

·    Destroys natural dams and causes flooding further downstream.




Industries  produce waste that can affect the:


·   pH of water (whether it is acid, neutral or alkaline);

·   colour of water;

·   amount of nutrients (increase in nutrients can cause eutrophication);

·   temperature (increase or decrease in temperature can have an impact on temperature sensitive organisms living in the water);

·   amount minerals and salts (too much can cause health problems);

·   murkiness of water (can block fish gills; bottom dwelling plants cannot photosynthesize as the suns rays cannot reach them; increase in disease as bacteria and viruses use the soil particles as a method of transportation).




Mines produce waste that:



·   can increase the amount of minerals and salts in the water (too much can cause health problems);

·   can affect the pH of the water (whether it is acid, neutral or alkaline);

·   can increase the murkiness of the water.




·   Increases soil erosion due to the physical disturbance of soil and vegetation due to ploughing, overgrazing, logging and road building. 
This affects the murkiness and the amount of salts and minerals in water;

·   Increases  nutrients due to fertilisers and excreta, which contribute worrying amounts of nitrates and phosphates to water supplies (this can cause eutrophication);

·   Increased pesticide use.


Energy Use


As human populations increase, more energy is required for human activities such as cooking, lighting, etc.  The majority of our energy in South Africa comes from the burning of coal at power stations and results in greatly increased emissions of sulphur and nitrogen oxides into the atmosphere.  These gases are the main cause of acid rain, which has a negative impact on the natural environment and human health.


Accidental Water Pollution


Accidental water pollution can arise from many sources (such as burst pipes and tanks, major leaks, fires and oil spills) and can cause varying degrees of damage, depending on the quantity, toxicity and persistence of the pollutant, and the size and adaptability of the water body.




The substances that cause water pollution can be divided into two main groups - germs and chemicals. Germs are small organisms that cause diseases such as malaria, cholera and bilharzia, and chemicals are poisons, which are mainly produced by industries.


1. Possible Poisonous Chemicals in River Water


Natural chemicals are found everywhere in the environment. Unfortunately, many of the chemicals that are produced by industries are not found naturally in the environment or are only found in very small amounts. Different industrial processes produce different types of products and waste products. Unfortunately many industries release their waste products directly into rivers or let them leak into the groundwater. These chemicals are poisonous or toxic to plants, animals and people. Some examples are:




Insecticides are chemicals that are sprayed onto crops to kill the insects that eat crops. One of the more controversial insecticides is DDT. The use of DDT on crops was used to control the malaria mosquito in South Africa.  At certain levels (10 mg per kg) DDT can cause human poisoning with the following symptoms: dizziness, vomiting and convulsions. At lower levels, DDT can affect the development of babies and has been associated with cancer.  DDT has been banned in South Africa. 

Another group of controversial insecticides are the Organo-phosphates. These insecticides have been used in the place of DDT since it was banned. Some specialists believe that these insecticides have caused even greater environmental damage than DDT and that they are even more toxic to humans and other mammals.


Insecticides are easily washed by the rain into streams and ground water where they poison fish and domestic animals. Many insecticides are stored for a long time in the bodies of animals and can end up in the meat, fish, egg and milk that you eat. Fruits and vegetables that have been sprayed with insecticides also remain poisonous for many days afterwards and must be washed very well before eating.

Ask questions about the use of insecticides in your area. Keep a look out for fish or birds that have been poisoned.  Dead fish and birds provide a good indicator of chemical pollution. If you suspect pollution by insecticides then contact your local council as soon as possible.




Heavy metals such as nickel, molybdenum, zinc, cadmium and lead are mined and processed by the mining and ore-smelting industries, many of which occur in Gauteng. These metals are easily washed into streams and groundwater. Copper and mercury are another two heavy metals, which are found in fungicides. Fungicides are also sprayed on crops and easily washed into rivers.  These heavy metals are toxic to biological life including the people who may have to drink from the polluted rivers. Crops that have been irrigated with polluted water can also be dangerous. In a similar way to DDT, heavy metals can also build up in the body causing symptoms of poisoning.

In the past, toxic waste products were dumped into the rivers or into landfill sites close to where people lived causing health problems and even death. Today all South Africans have a constitutional right to a clean and safe environment. Make sure that you remain informed and observant so that you can prevent toxic chemicals from being used in your environment.

If you suspect water pollution in your area then contact your local council.




We all know about the destruction that oil pollution causes along the marine coastline.

However, a lot of oil pollution also occurs inland. Petrol and diesel is stored in underground tanks at petrol depots. When these tanks are not properly maintained, they can develop cracks allowing the petrol to leak out. Many people are also very negligent when changing the oil in their car engines.  Many people just throw the oil onto the ground! 


This oil and petrol is washed by the rain into the groundwater. This ground water eventually surfaces at boreholes and wetlands. In the past, ground water was considered clean since chemicals and germs were not present, but this is changing very quickly. Groundwater is becoming more and more polluted with a number of toxic substances including insecticides, petroleum products and heavy metals. South Africa is a dry country and as the human population grows, our groundwater is becoming very valuable. We must all work towards keeping this resource as clean as possible for the future when we really need it.




Paper and pulp mills and textile factories are amongst the worst water polluters. Paper and pulp mills use up large amounts of water and produce a lot of polluted wastewater. The wastewater contains strong chemicals such as chlorine, which is used to make paper white and soft. Textile factories also release strong chemicals like caustic soda, acids, dyes and detergents into water. 


These strong poisons also cause bird and fish kills similar to insecticide poisoning. These chemicals are also directly poisonous to humans. Ask questions about what industries occur in your area and how they release their wastewater. Do not drink water that is downstream from a factory that releases wastewater into the river.

Remember that the detergents that you use at home are just as poisonous so use only biodegradable products. Read the label on the product that you are buying, this will tell you what the product is made of and if it is environmentally friendly.




2. Fertilisers and Sewage


Some chemicals like fertilisers are made of substances that do occur naturally in the environment, but only in small amounts. When too much fertiliser is washed from farmlands into a river then that water will also become polluted. Human sewage or cattle excrement that is untreated also causes water pollution in the same way as fertilisers do. Human sewage also contains germs that cause diseases such as hepatitis and cholera.  Soaps and washing detergents contain both natural and man made (artificial) chemicals. Artificial chemicals like bleach and chlorine were discussed earlier. The natural chemicals can cause a pollution problem similar to that caused by fertilisers.

Phosphates and nitrates are found in fertilisers, sewage and soaps.  Phosphorus is an essential element for life, both as a nutrient for plant life and as a key element in the metabolic processes of all living things.  The normal low phosphate (PO4) level in water inhibits the growth of plants but a small increase of phosphates can result in a rapid increase in plant growth such as blue-green algae and water hyacinth, especially in dams. 


The water plants become overcrowded and die.  When they die the decomposing bacteria uses up more oxygen and affects other forms of life badly, eg. fish suffocate.  This process is called eutrophication, and can be increased by human activities, eg.domestic effluent (especially soapy water), farm and lawn fertilisers, industrial effluent and the destruction of wetlands. 

Nitrogen in the form of ammonia (NH3) and nitrates (NO3) form part of the plant nutrients that can lead to eutrophication. 


Nitrate enrichment through sewage contamination and fertiliser runoff is not as critical as it is with phosphates because aquatic ecosystems are not as sensitive to increases in nitrate levels.  Nitrogen normally occurs in a form that plants cannot use (i.e. nitrogen gas), however, it may be used in the decomposition of dead water plants and by blue-green algae which can convert nitrogen in the air into ammonia and nitrates that plants can use.  This subtle interdependence illustrates the complexity of the relationships within an aquatic ecosystem.  The best way to stop this kind of pollution is to prevent human sewage, cattle excrement and fertilisers from washing into rivers.


Blue-Green Algae


Blue-green algae are microscopic inhabitants of rivers.  They liberate oxygen into the water, take up mineral nutrients and produce substances which enter and support food chains in the aquatic environment.  With a rise in river pollution there is an increase in nutrients.  This causes a great increase in the growth of blue-green algae, which are called algal blooms.  These blooms have an effect on the colour, taste and odour of rivers.  Human contact with these algal blooms can cause illness, such as hayfever, skin rashes, eye irritations, vomiting, gastroenteritis, diarrhoea, fever and pains in muscles and joints.


3. Water Pollution and Disease


Most diseases in the world are related to water and sanitation. To break the cycle of disease, there must be improvements in the quality of water that people use. Most rural communities in South Africa do not have access to running water, toilets or latrines and they use watercourses for defecation and urination. In many cases, where they are present, latrines are situated upstream from where the community collects their water supply.


Faecal pollution of water increases the risk of infection of various diseases to those using these courses as their life supporting water source. Groundwater, which is another water source, can become contaminated through unclean irrigation water. Water related diseases could be spread in other ways, which also affect urban communities, such as insect bites and poor hygiene.

Although there are many more, these are some of the most common water – related diseases in South Africa:




This occurs, like most diseases, in a cycle with a parasite and different hosts. Bilharzia only occurs in areas where conditions are right for the parasite to be able to complete its life cycle.  The adult parasite is a worm that lives in the bladder or intestine of humans (the 

main host). They mate inside the body and eggs are released in the urine or faeces of the host. If an infected person defaecates and urinates into the water, the eggs hatch into the swimming form of the parasite. It then burrows into the body of a snail (the intermediate host). The snails favour slow moving water with plenty of vegetation. Here the parasite changes form and exits out into the water again. This is the stage that infects humans. If a person has contact with contaminated water the parasite will penetrate their skin and move through the body causing illness.  Some symptoms of Bilharzia: an itchy rash, headaches, abdominal pain, diarrhea, bladder infections, fever, enlarged liver and swollen veins.  Within South Africa, Bilharzia is most common in the Northern Province, the Lowveld and KwaZulu –Natal.





In South Africa Malaria is given very high priority. This disease, which also occurs as a cycle, is caused by a parasite that is transmitted by some species of female mosquitoes. The female mosquito requires a blood meal in order to obtain sufficient energy and nutrients to produce her eggs. When a mosquito bites a human, it injects saliva into the bloodstream to prevent the blood from clotting. If the mosquito is infected with the malarial parasite, the parasite will be released from the mosquito’s saliva into the blood of the human. The parasite travels through the body and enters the red blood cells. The red blood cells eventually burst releasing the parasite into the blood stream where it is ready to be sucked up by the next mosquito. Mosquitoes breed in water, especially dams, ponds, water tanks, old car tyres, and other hollow objects that can hold water, like tins.  The best way to protect yourself from Malaria is not to leave litter lying around, and to prevent getting bitten by wearing long sleeve clothing and by applying insect repellent to your skin, especially at night.  Some symptoms of Malaria: fever, headache, diarrhoea, nausea, joint and muscular pains, shivering, sweating and fatigue.  Malaria is distributed in the Northern Province, Mpumalanga, Northern KwaZulu – Natal and parts of the northern Cape.




Cholera is a disease that is caused by bacteria (Vibrio cholerae)  that is spread through water contaminated by faeces from an infected person. The bacteria produces a toxin that causes the small intestine to secrete large amounts of fluid, which leads to fluid loss, i.e. diarrhoea and vomiting.  People who do not wash their hands after using the toilet can spread the disease. It can also be spread when human faeces is used as a fertiliser for vegetable crops. It is important to remember that even if a person does not show symptoms of the disease, they could still be infected and spread the disease. Cholera can be found in most places where there is poor sanitation.  Some symptoms of Cholera: diarrhoea and vomiting. People who have the disease should drink plenty of clean water to prevent dehydration.


Important Things That You Can Do to Decrease the Risk of Disease.


·   Do not defecate or urinate near water sources;

·   Wash your hands with soap and water after going to the toilet;

·   Do not drink water that you think might be unclean - boil it if you are unsure;

·   Wash all fruit and vegetables well before eating them & do not cook with unclean water;

·   Do not leave empty containers or any litter lying around for disease transmitting insects to breed in;

·   If you have access to pit latrine facilities, ensure that they are away from sources that are used for drinking and bathing. The pit should not penetrate groundwater. 


·   If you don’t have a water purification station to clean your river water what can be done to clean the water? 


There are 3 ways to make your water safe to drink:



Boiling water kills any germs that might be in the water.

Step1: Boil water in a pot.
Step2: Allow to cool.
Step3: Keep this boiled water covered with a lid or clean cloth to protect it from being contaminated by flies and dirt.


Adding Bleach


Bleach is strong smelling and contains chlorine which kills harmful germs in the water.

Step1: Buy a bottle of Jik, Jewel or any other kind of bleach from your local shop.
Step2: Add one teaspoon of bleach to 20 litres of water.
Step3: Allow to stand overnight for a minimum of 2 hours.
Step4: Keep the water covered with a cloth or lid to keep out flies and dirt
Your water is now safe to drink.

Adding Chlor-Floc

Chlor-Floc is a substance that makes muddy water clean and safe to drink.  It can be bought from a chemist and is available as a powder or as tablets.

Step1: To use Chlor-Floc mix one teaspoon of powder with 20 litres of water and stir for a few minutes, or follow the instructions on the pack carefully.
Step2: The dirt will soon settle to the bottom of the container.  The clean water should be filtered through a cloth.  The dirt will be left on the cloth.
Step3: Be sure to keep the clean water covered.
(Reference: Umgeni Water)



The tributary streams of the rivers draining both the southern and northern Gauteng Province are severely impacted by mining, industrial and urban activities.  The Jukskei River drains the northern part of the densely populated and industrialised Gauteng Province before flowing into the Crocodile River.  The Crocodile River drains the Hartbeespoort Dam, which is a popular recreational area and serves as a raw water source for the North West Province.

Three main rivers drain the southern Gauteng Province, namely the Klip, the Riet and the Blesbos/Suikerbosrant Rivers.  These rivers flow through a variety of communities before they join the Vaal River Barrage Reservoir.  Within this whole region large Phragmites and Typha (types of reeds) wetlands occur which filter and hold water, slowly releasing it into surrounding habitats and communities.  Although most of these wetlands have arisen due to human intervention they, for the greater part, are invaluable in the protection of rivers. 


Wetlands and vleis present in the rivers draining southwards (to the Vaal River Barrage Reservoir) play an extremely important role in the natural upgrading of the water passing through them and should be protected.  In addition to this valuable function they also act as a green “lung” and are home to a great variety of birds.  Silt, originating from various old mine dumps, covers the bottom of rivers and is detrimental to most forms of water life. 


Here again wetlands come to the rescue as they retain the silt, thus protecting the downstream sections of the river.  Rivers draining northwards (to the Hartbeespoort Dam) have few wetlands and flow rapidly due to the relatively steep slopes, carrying relatively high loads of suspended material.  Any drop in the speed of the rivers will cause the coarser material to settle to the bottom causing the various weirs and dams to rapidly fill with silt.




Many people in Gauteng receive their water from taps. The water that comes out of these taps is very clean and healthy for humans to drink. This is because the water has gone through a major cleaning process. Rand Water is the company that cleans the water in Gauteng. This water is originally taken from the Vaal Dam.  Rivers such as the Vaal, Klip and Wilge Rivers naturally flow into the Vaal Dam. These rivers flow through agricultural land and rural settlements with very little industry. 


This means that the water in the Vaal Dam is of a good quality by international standards. From the Vaal Dam the water is transported via canals and pipelines to a water purification station. Rand water has two water purification stations in Vereeniging. When the water passes through the water purification process all the dirt particles are taken out of the water and all the germs are killed by a disinfectant called chlorine. Once clean, the water is pumped into reservoirs and then it flows into your taps. It is there that you receive enough clean water.




South Africa has, in general a limited supply of water and the quality of this water is being threatened by pollution and the destruction of river catchments. Water in South Africa is in great demand, and as the human population grows with its increasing needs for survival, the greater the demand for water becomes. With this demand there is an increase in pollution and catchment destruction and a decrease in the quality of river water and natural environment.


If we are experiencing this water situation now, what will happen in the future?

South Africa can build more dams and water transfer schemes, but this type of infrastructure is expensive and South Africans cannot financially afford them. In terms of “water quality, South Africans can clean up rivers and impose fines on those people / companies that pollute rivers. But these solutions address the symptoms of the problem. We should be addressing the cause of the problem, i.e. the lack of water conservation in our daily lives.

The real solution is to change our attitudes towards water. South Africa needs to become “Water Wise”.


To be “Water Wise” means that a person will:


·  have the utmost RESPECT for water and all life;

·  use water carefully and not WASTE it;

·  not POLLUTE rivers with liquid and solid waste;

·  PAY for water services;

·  take ACTION to solve any water problems;

·  CONSERVE water, and thereby CONSERVE the natural environment.


(Information produced by The Water Wise Education Team,
Scientific Services Division)


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