The introduction of appropriate technology in water supply and sanitation projects is still a more or less untested field. Hopefully, its promotion by the International Water Decade will remedy that situation.

In the course of the Water Decade much has been publicized on this theme. On the technical side, for the most part, the solutions put forward have dealt with the familiar concepts of simple technology that was used in the industrialized countries in earlier times (handpumps, latrines, cisterns, etc.). There is also no lack of planning ideas to realize these designs. The inclusion of the local conditions, the active participation of the populace, and integrated approaches are also spoken of, but the practical conversion of these concepts by bi- and multinational donor organizations has been tried in very few cases. Most approaches don't make it beyond the research and demonstration phase.

Taking the step of that conversion means confronting the individual for whom the technology is meant. Here one is up against an area whose theoretical evaluation can collide with the practice - where the technique becomes meaningless, which is why an assessment of its success is problematic.

The structural limitations imposed' exempt all 'but a very few organizations which are capable of carrying out projects whose social components are in the foreground. These limitations include the pressure for success, the disbursal of large sums of money in a short period of time, as well as political interests of donor and recipient countries. The aformentioned social components are precisely what is necessary to satisfy those basic needs put forward as the first priority goal of the Water Decade.

It is often said that the treatment of drinking water can not fall under the heading of appropriate technology. The reasons given are that the operation and maintenance are too difficult to manage for the local populace, that needed materials (like chemicals) and equipment (laboratories necessary for carrying out analyses, etc.) are not available in technically backward areas.

Steps should and could be taken towards developing more appropriate and economical solutions such as: adjusting the quality standards, using locally available construction and filter materials, substituting chemicals through alternative materials, i.e., treatment processes (as far as possible), a further development of traditionally used water purification techniques, and modifying model design for simple replication.

It is frequently suggested that as an alternative to treating surface water, ground water be used, because it is generally free of bacteriological contamination. There are basically two problems with this suggestion. The first is that the entire ecological effects must be taken into consideration -for example, the abundance of groundwater thus made available could attract livestock and lead to overgrazing with all its consequences. The second is that increased costs would be incurred, and sophisticated equipment required, if the groundwater was not found close enough to the surface.

There can be no strict rules concerning which technology should have priority. It is important, however, that the entire range of technological possibilities be always considered in order to guarantee a sufficient quality and quantity of drinking water supply. The final decision over a suitable technology must take into account the particular set of local circumstances.

This brochure attempts to describe methods of drinking water treatment that emphasize simplicity and small scales, for areas which presumably have limited technical and financial resources at their disposal, and where the level of education and skills is relatively low. In general, there are two categories that must be distinguished:

1. Treatment on the municipal level as part of an already existing or newly installed piped water supply system.

2. Treatment on the individual level within a single household.

These two categories foundamentally. differ in:

- scale,

- technological niveau,

- the responsibility of the individual for the plant.

The first category seems simpler since the individual does not play as prominent a role and the plant can function on an intermediate technological level. When deciding on a particular technology, the criteria mentioned at the outset should be adhered to, in order to keep costs down and to avoid downtimes due to missing spare parts or irreparable mistakes by the operating personnel. In this regard, several studies have been conducted to simplify conventional designs and improve already known and technically simple alternatives.

The second category is somewhat more problematic in that it requires the active participation of the individual. The user is simultaneously the one responsible for proper operation and maintenance of the apparatus. This brings with it the risk that mistakes can easily occur. But for reasons of safety, effective functioning of the apparatus is essential.

Building on traditionally known and used water treatment practices, carries the potential for success. It is safe to say that the implementation of programs is only possible through regional mediators who are in close personal co,ntact with the population. There are few successful examples known on the household level. Likewise there is a lack of tested simple and safe technologies that can be employed on the local level.

In conclusion we can say:

- The treatment of drinking water is primarily a matter of hygiene, which belongs in the personal sphere of the person who's going to use it.

- These kinds of measures are not solely a technical problem, but, more importantly, involve instruction, motivation and education in the area of personal hygiene and responsibility for the environment regarding the cause of contamination.

Technically, the production of safe drinking water entails:

- the treatment of available, contaminated water,

- consideration of alternatives (groundwater, repair and improvement of existing facilities, rainwater collection and storage, etc.),

- the provision of sufficient quantities,

- management, i.e., collection, treatment, disposal and reuse of refuse, wastewater and fecal matter.