Careful consideration should be given to all the technical factors described in Chapter 5 in order to select a number of appropriate types of latrine from those described in Chapters 4 and 6. A decision tree, like that shown in Fig. 9.1, may serve as a framework for selection. In effect, use of such an approach may eliminate some forms of sanitation, leaving others for further consideration.
Factors that are relevant in deciding whether a sanitation system that is technically feasible should be offered to householders and communities include the following:
• whether the system appears to be popular, as demonstrated by the number of householders who have already adopted it or by widespread interest in possessing it;
• the extent to which its use would fit in with local cultural and religious customs;
• the extent to which it would reduce pollution and health risks;
• the ease with which it can be provided by the people themselves, having regard to local skills and easily available materials;
• the cost, and particularly the cost of any materials, components and labour that cannot be provided by the householders;
• the ease with which it can be operated and maintained.
Having selected a number of options that are appropriate, the costs of each option can then be estimated. These should relate to a range of construction methods and materials. The total cost in both financial and economic terms of providing the required number of units for the project may then be calculated. Some agencies may favour least-cost solutions for externally funded projects, as discussed in Chapter 10.
When suitable options have been selected, the agency or the community itself must then go on to provide the latrines, giving each individual householder the maximum possible opportunity of choosing between alternative types, materials, finishes and other details. The stages in the implementation process are discussed in Chapter 11.
Fig. 9.1. Decision tree for selection of sanitation
Note 1: Not all possibilities are illustrated as it is assumed that water availability is related to affordability.
Note 2: Use extra-large pits or consider composting.
Note 3: Also dependent on willingness to collect urine separately, demand for compost, availability of ash or vegetable matter, etc.