|Public Health Technician (MSF, 1994, 192 p.)|
|II - Sanitation|
The accumulation of household waste creates a public health refuse as well as a pollution problem.
The health risks are essentially to do with the encouragement of insect vectors and rodents:
- the breeding of flies which play a major part in the
transmission of f-oral diseases;
- mosquitoes of the Aedes genus which lay eggs in water lying in empty tins, drums, tyres, etc., and which are responsible for the transmission of dengue, yellow fevers and other arboviruses;
- mosquitoes of the Culex genus which breed in stagnant water heavily loaded with organic matter, and which are liable to transmit microfilariases;
- rodents which are directly or indirectly responsible for the transmission of various diseases such as plague, leptospirosis and salmonella, and whose presence attracts snakes.
In addition to these health risks, poor management of the collection and disposal of refuse may involve the pollution of surface water or groundwater and increase the risk of fire. Lastly, the aesthetic aspects (sight and smell) are far from negligible.
These risks and nuisances are all the more serious at high population densities.
Certain types of refuse (from medical activities) represent a particular risk and so need special attention.
Type and quantity of refuse
The type and quantity of refuse produced by a community are extremely variable.
The main factors affecting the composition of refuse are:
- geographic region;
- sociocultural, cultural and material levels, which may produce great variations even within the same community;
- seasonal variations;
- the importance and diversity of refuse-generating activities (workshops, dispensaries, etc.);
- packaging of food ration.
The density of refuse is in the order of 100 to 200 kg/person/day and the volume varies between 0.5 and 101/person/day; an average value of 0.5 litre/person/day may be taken.
The percentage of putrescible matter may range from 20 to 70%.
These few figures simply present orders of magnitude, and in practice the quantity and density (or volume) of refuse should be determined for each situation. Its composition is only really important when disposal is by means of incineration or composting.
In general terms it may be assumed that the volume of refuse will be small when dealing with a population of rural origin and where the basic ration is in the form of dry foodstuffs (as is often the case during the initial phases of an emergency operation).
The objectives are:
- to gather the refuse to facilitate the collection;
- to avoid dispersion by wind and animals.
Metal drums are generally used. The bottoms should be pierced so that they do not retain liquids from decomposition (and to avoid the drums being used for other purposes), and they should be provided with covers and with handles for easy lifting. In the first instance one drum per ten families may be provided, placed at a reasonable distance from the dwellings.
Certain structures need particular storage systems, either because of the specific nature of the refuse produced (hospitals), or because of the large volumes produced (market, slautghterhouse, various workshops). In these cases, solid, covered and easily cleaned bins may be built. In health centres, refuse is collected in separate containers: some dustbins are available for ordinary refuse and others, clearly marked, are used only for medical waste.
Collection should be done at least once per week to avoid the hatching of flies and odour problems. In practise the use of a whole chain of different resources need to be optimised, but a daily collection is the ideal.
The collection of the contents of dustbins (without forgetting the surroundings) may be done with vehicles. But it may be more reliable logistically to use hand carts or animal carts. Moreover, it is difficult in emergency situations to commit a vehicle exclusively to this task.
The collection should be organised:
- establishment of circuits,
- constitution of teams,
- allocation of a circuit to each team.
After its introduction the collection system should be supervised and evaluated periodically. (Is the circuit appropriate? Are the resources enough?)
These two steps of storage and collection require the co-operation of the population, which should be involved regularly (once or twice per month) in a general clean-up of the camp.
Three techniques are used
Burial is done in trenches. Controlled tipping (see brief Controlled tip) is only used where there is sufficient space and access to mechanical equipment.
Access to the site should be restricted (a fence). If good drainage is not ensured, there is a great risk of the trenches turning into sickening quagmires.
The siting of the trenches should follow the same rules as for siting latrines, as the risk of polluting the water table is the same.
Medical waste should be incinerated as it is potentially contaminated.
This method is not generally suitable for household wastes as it is costly and may be dangerous when it is done on a large scale (atmospheric pollution).
Composting is biological decomposition in the presence of air, as opposed to anaerobic decomposition which takes place in septic tanks for instance.
It is a technique which needs special care and which may cause major health risks if not mastered correctly. For this reason it should not be used in emergency situations.