SAND FILTER SYSTEM: A MEANS FOR SOLVING DOMESTIC SEWAGE DISPOSAL PROBLEMS IN RIVERINE AREAS

Abstract

The relative effectiveness of the "Soak-away pit" system and the "Sand-filter" system in the disposal of domestic waste in the riverine area of the Niger Delta has been investigated as presented in this paper. This investigation was prompted by observed proliferation of the soak-away pit system with attendant environmental pollution problems in many Niger Delta communities witnessing rapid urbanisation. In many instances inappropriately disposed sewage has contaminated both the soil and the underground water harnessed for drinking, and also destroyed the aquatic life of streams especially where the waste found its way into such water bodies. Field and laboratory test results indicate that the soil underlying the area is silty Clay with a low acceptance rate (5.21litres/m²/day), low percolation rate (218 min/100mm), high ground water table and, in most cases, prone to flooding above grade level in the rainy season. These parameters indicate that the soil is semi-impervious and hence the soak-away pit system would be of very low efficiency in the domestic waste disposal in this area. The "Sand-filter" system, on the other hand, is portrayed by the results as having a high potential of providing the required treatment capacity for the type of soil underlying the area and is therefore efficacious for domestic sewage disposal in this deltaic environment. The "Sand-filter" system is therefore recommended in preference to the "Soak-away" since the soil properties revealed by the test programme cannot allow a satisfactory post-construction performance of the soak-away pit system of domestic sewage disposal.