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cient to deal with rapid development. An example is provided by the Hayatabad treatment works in Peshawar which serves a large and generally successful government sites-and-services scheme aimed primarily at middle and upper income people. The works consists of aerated lagoons followed by facultative and maturation waste stabilization ponds. Performance was satisfactory for about 3 years and then began to deteriorate as flows from areas which had not been allowed for in the original design were diverted to the works. Land had been set aside to extend the works but there was no political will to provide finance for the extension. The deterioration in performance showed itself mainly in the form of increased odour problems and after complaints from local residents, much of the flow was diverted around the works without treatment, thus removing the reason for the works being there. (It is worth noting, however, that the facultative ponds appeared to operate satisfactorily at rather higher loadings than is assumed by current process design guidelines.) |
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The first broad conclusion to be drawn from this chapter is that approaches and technologies exist to provide sewerage at the local level, making it an affordable option for low-income communities in many circumstances. More needs to be done to convince governments that appropriate standards are technically acceptable. Community involvement in sewer planning and construction is possible at the local level but government or some other agency must provide some technical and organizational support, at least in the early stages of any programme. In general, government will have to retain the responsibility for the provision of higher level facilities, but the ability to extend these facilities to keep pace with rapid development is often limited. There are theoretical reasons for decentralizing sewage disposal systems to a considerably greater extent than would be sensible in high-wage economies, but there are many practical questions to be resolved about such decentralization. This suggests that a main focus of research over the coming years should be on obtaining answers to these questions. |
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