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Computer software of SANEX: Description of procedure and capability

The purpose of this computer program is to support decision makers and project beneficiaries in identifying feasible alternatives and in evaluating the adequacy of these alternatives with respect to community circumstances. The three questions which the program attempts to answer are:

  1. Which sanitation technologies are relevant to rural and urban communities in developing countries?
  2. Which are the relevant criteria to evaluate the appropriateness of these technologies?
  3. How can these criteria be incorporated into a decision aid that can be applied by decision makers to concrete projects?

Two-Stage Evaluation
This model features two distinct evaluation stages (Diagram A). During the screening stage, infeasible alternatives are eliminated based on mainly technical criteria. Subsequently, during the comparative stage, the remaining alternatives are compared with regard to the indicators implementability and sustainability. Apart from technical issues, this stage considers numerous sociocultural objectives. Implementability expresses the probability that sanitation facilities can be constructed within the period and with the financial resources usually required in favourable conditions. Sustainability expresses the probability that facilities serve beneficiaries according to their design throughout their design life.

Diagram A: Screening evaluation is symbolised by the screen (1) which lets only technically feasible options (represented by the smaller spheres) pass. Comparative evaluation is symbolised by the horizontal bar graph (2), indicating performance for each feasible option.

Multi-Level Amalgamation

A major obstacle to formulation the comparative component of the algorithm was the amalgamation of numerous criteria outcomes. The application of conventional methods, such as the arithmetic mean, would have resulted in a diminishing effect of the individual criterion. In order to preserve the effect of criteria, a new method for amalgamating criteria on multiple levels was developed, which would also allow the simultaneous application of various methods like the arithmetic and the geometric mean. The combined advantages of multi-level amalgamation are reflected in more plausible evaluation results.

Costing of Sanitation Alternatives

Assuming the planners in developing countries usually have sufficient access to financial expertise, no criteria to assess the affordability of sanitation systems were formulated. Instead, it was decided to develop a costing model that would enable the proposed decision aid to estimate the capital as well as the recurrent costs of all alternatives. Further, a simple method based on the local residential building cost was developed to convert these estimates to costs in local currency units, as they would occur in the project area.


The above work resulted in an evaluation model for assessing the implementability, the sustainability and for costing sanitation alternatives in developing countries. In 1998, in order to validate this model, a second journey was undertaken to Southeast Asia and to Europe. Based on the application to nine case studies, several modifications emerged to be necessary.


The expert system software SANEX© was developed for the MS Windows operating environment. The knowledge base of this software contains more than 80 sanitation alternatives, which are combinations of the technologies outlined in the table below, and uses around 50 technical, sociocultural and financial criteria for their assessment. The costing component employs approximately 50 functions.

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