4.4 Protection from pollution
The control of pollution should ideally take place at the point of its generation. In Study Session 3 you read about the methods of protecting water sources but it is better to prevent the pollutant from entering the environment in the first place. With regard to human excreta, this means an end to open defecation, the correct siting and construction of latrines and septic tanks, and well-maintained and correctly operated sewage treatment works. Industrial wastes should be treated at source before discharge. Other human activities should also be controlled; for example, used engine oil should not be thrown onto the ground, and solid wastes should be carefully disposed of. A positive measure that can help to prevent soil erosion is to preserve vegetation and plant trees, because plant roots hold the soil in place.
In rural areas, the control of excess nutrients is important to keep natural waters free from eutrophication. Farmers may need guidance on good agricultural practices to reduce water pollution from agriculture. For example, care over the amount of fertiliser used and the timing of its application can make a significant difference.
Imagine you are a farmer thinking about the best time to apply fertiliser to your field. Would it be better to spread the fertiliser before or after heavy rain?
It would be better to apply it after the rain because if the fertiliser was spread beforehand, much of it would probably be washed away. This would not only pollute the nearest river but would, of course, also reduce its effectiveness on the crop.
Pesticides should not be applied near wells or other water sources. If possible, biological methods of pest control should be used. Examples of these are the use of fish to feed on mosquito larvae in water bodies, and the use of the dung beetle to break down and bury cow faeces so that they are no longer available as a breeding place for flies.
Ideally, the whole catchment area should be managed to avoid pollution and erosion. To tackle pollution problems, especially diffuse pollution, all activities within a catchment should be considered. This involves many groups (residents, planners, farmers, etc.) working together, on aspects such as granting permissions for development, compliance with regulations, inspections of activities, and regular surveys and investigations of water pollution.
4.3.5 Urban surface water run-off