Abstract:
Over the years, Silica sand has been used as a filter media in both developed and'
developing countries. However, not until recently when research works showed that
locally available sands in Nigeria were useful filter media in rapid sand filters, sand
stocks used in filters were imported alongside with the treatment plants. The essence of this thesis is to revisit earlier work done on local sands and consider its application in slow sand filters. In the light of this, locally available sands were collected from three sources viz: Igbokoda, a location in Ilaje Local Government Area of Ondo State with abundant 'white' coastal sand used for glass sheet location in Akure North Local Government Area with a typical sand quarry. used in local construction works.
The sands collected were analyzed to determine their desirable properties 'as
required in slow sand filters. A model slow sand filter box was constructed in which the
analyzed sands were used as media to treat raw water of varying degrees of impurities.
The resultant effluent qualities were analyzed to determine the filteration effectiveness
achieved, using the sand stokes.The results show that the three sand stocks studied had negligible solubility in 40 %Hcl, indicating that the material is a whole grain, free of fossile. The sands have a specific gravity range of 2.65 to 2.67, indicating that the sandstocks are good silica sands. Within the specified range of particle sizes for slow sand filters, the Igbokoda sand produced the highest yield of usable sand and a better effluent quality in terms of turbidity removal. However, the Igbokoda sand-bed clogged more rapidly as a result of having higher percentage of fine grains. In order to avoid a need for frequently cleaning of this stock, the percentage fine should. be regulated.
