Unit F2


Any community produces wastes. A traditional community produces wastes that come from the local environment and that can usually be absorbed and disposed of by that environment. A more modern community imports many things which are usually thrown away locally after they are used or worn out. Often these things do not decay rapidly and thus they stay in the environment for a long time. Any time many people are living together, they also produce more human waste than the local environment can absorb. All these wastes can be a threat to human health.

In order to control the spread of diseases, everyone must learn and follow the principles of good hygiene, including personal cleanliness, safe disposal of human wastes (faeces or excreta), hygienic food preparation in clean surroundings, careful disposal of garbage, and a pure water supply. The sanitary and environmentally safe disposal of wastes is often a particular problem on small islands where the land area is limited, the coastal waters are important for fishing, and it is not easy to find any place the islanders can afford to set aside for wastes.

Solid waste disposal

The solid wastes produced in any modern community are of several kinds. There are organic wastes such as paper, kitchen garbage, and garden cuttings which will decay with time and may even enrich the soil. They may, however, be contaminated with disease organisms. There is metal in various forms, including steel and aluminum cans, old automobiles and appliances, and metals used in construction. Some like steel will slowly rust away or oxidize, while others may remain almost indefinitely. A few, like the heavy metals lead and mercury, may be poisonous if they contaminate the environment. Glass is usually in the form of bottles, which may break but not rot, and which frequently cause serious cuts and accumulate water in which mosquitoes can breed. There are now plastic wastes in many forms, including plastic bags, bottles and packaging, old ropes and nets, synthetic clothing, and many household objects.

If solid wastes are just dumped or used as fill, they can become a breeding place for flies, rats and mosquitoes. Since some of the wastes may be contaminated with poisons or diseases, it is dangerous to allow people to sort through and remove things from the dump. Island people have died after eating food found at the dump. Wastes can also be a source of significant water pollution, either in water running off from the dump site or in ground water contaminated by seepage from the wastes. If the wastes are burned, the smoke can be a significant source of local air pollution, and may contain toxic gases.

There are sophisticated techniques for destroying solid wastes like high temperature incinerators, but these are beyond the means of island countries. The most widely used disposal method is the sanitary land fill. A site should be chosen where there is no risk of contaminating important water supplies or coastal waters. The wastes are dumped, compacted, and immediately covered with a layer of dirt or other fill. The method is simple and relatively cheap; availability of fill material is sometimes the biggest constraint.

Liquid waste disposal

Water pollution, usually by liquid wastes, is the most widespread environmental problem in islands. Some of these wastes come from industries, but most are the result of people's use of water for washing, cleaning and in water-flush toilets. Some water pollution also results from heavy rain flooding pit toilets or latrines. Liquid wastes from areas where people live are thus usually highly contaminated with microbes including disease germs, viruses and parasites.

While the natural environment has some capacity to purify such wastes, it is quickly overloaded by the concentration of people in large villages or towns. This creates serious health risks if safe ways are not found to collect and treat these wastes.

Liquid wastes follow the drainage patterns of the land, often going into streams, swamps or ground water before finally emptying into the coastal waters. Thus each watershed in a town area may have different liquid waste problems. The amount of waste will depend on the number and concentration of people living in the watershed.

The appropriate techniques for treating human wastes depend largely on the density of the population, and to some extent on the nature of the soil and the risk of polluting water supplies. A well-designed closed or water-seal latrine may be adequate for an isolated family in a rural area. A low density community will usually require septic tanks in which the wastes are partly purified before being spread through the soil in a drain field for final treatment. Septic tanks need to be properly designed and emptied regularly; otherwise they will not do their job and cause pollution. In most islands, very few septic tanks are properly maintained. People usually wait until they are completely stopped up before having them emptied.

In larger towns and cities, septic tanks are no longer adequate, and liquid wastes will need to be collected in sewers for central treatment. There are many treatment methods, including oxidation ponds and various kinds of waste treatment plants. Experience has shown that the more complicated systems are difficult to maintain in small island countries, so simple treatment methods should be chosen whenever possible. The use of the output of these systems to water flower gardens or golf courses can help to complete treatment, but this is not recommended for food gardens as there is a slight risk of contaminating the food. Treated waste water can also be drained into coastal waters where the circulation is good, preferably into the ocean beyond the coral reef if one is present.

Toxic wastes

The increasing numbers of poisons and toxic chemicals being imported into island countries is creating special problems with waste disposal. Anything brought into an island is eventually released into the environment, either when it is used or when it is finally thrown away, unless it is exported again as the most dangerous wastes should be. Some of these poisons such as pesticides are applied in small amounts over large areas, but there are always residues left in the containers, contaminated or spilled materials, and poisons that were bought and then not used.

Most people simply pour unwanted poisons down the drain, or throw them out with the rubbish, and they thus end up in the liquid or solid wastes, where they add to the risks both to people and to the environment. There have already been serious accidents with such wastes in the islands, and it is best to assume that any poison used in your community will eventually turn up in the wastes, and take precautions accordingly. The developed countries are discovering too late that many old rubbish dumps are time bombs of poisonous chemicals that are now starting to leak into the environment as their containers disintegrate. While there is less chemical waste in the islands, all imported materials should be look at with care for their eventual effects when they are thrown away.

Evaluating hygiene and sanitation

The following check lists (based on ones developed by UNICEF and modified by Pacey, 1980), can be used to evaluate the state of hygiene and sanitation in a town, village or household. If the answer to any question is NO, then there is a possible health hazard which probably requires some action.

Environmental Checklist Part I: The village
(A NO answer shows a danger)

1. Do people defecate so that their waste is kept away from places where other people may walk, and where flies cannot reach it (such as by using a latrine or burying it)?

2. If children leave faeces near their homes, are they immediately removed?

3. Do people defecate far away from the source of drinking water?

4. Is the drinking water source different from the place where people and animals bathe, and women wash clothes?

5. Does the village have a protected water source, such as a protected spring, a well with a pump, or a piped water supply?

6. Do people use water from the protected source?

7. If there is a protected water source, is it conveniently placed for everybody? If there are wells, are there enough of them? If there is a piped supply, are there enough taps?

8. Is the area around the wells or the public taps dry?

9. Do people try to ensure that stagnant water is drained away, so that rain does not leave big puddles in the village?

10. Are there any waste burial pits or rubbish bins in the village?

Environmental Checklist Part II: The home and family
(A NO answer shows a danger)

1. If the household has a latrine, is it clean, and is there a cover or other means of keeping flies out?

2. Is the house clean and free from flies?

3. Does the family have clean drinking water?

4. Are there containers or cisterns for storing water, and are they covered and clean?

5. Is there a bowl and soap for washing hands?

6. Do people regularly wash hands after defecating and before eating?

7. Are the preferred materials for anal cleaning (such as paper) always available? Or if water is used, is it available near the latrine or defecation site?

8. Is there a way for young children to defecate hygienically in or near the house (such as a pot)?

9. If the household has pigs or other animals, are they confined in a pen? Is the pen clean?

10. Is there a waste pit or bin where animal droppings can be safely placed, and where children's faeces can be put?

11. Does the housewife throw rubbish into a waste pit or bin?

12. Is it possible to prepare food in a clean place, and if there is a kitchen, is it convenient for the housewife?

Instructions for trainers in the use of this unit

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UN System-Wide Earthwatch Coordination, UNEP, Geneva
Updated 7 April 1998