BY

Rotarian ( Prof) Gabriel O. Adeyemi FNMGS, FNAEGE, FNAH, AFF.ASCE, AMNSE.

Department of Geology, University of Ibadan.

Introduction: Rapid population growth and increased industrialization often led to generation of huge volume of waste in many part of Nigeria. The waste is disposed indiscriminately. This practice has detrimental impact on the environment. The odour that emerges can pose health problems while the environment often wears bad look. Heaps of waste can impede easy flow of rain water while waste may find its way to river channels.The resultant increase in volume of the content of river channels often results in the flooding of the environment. Structures such as buildings and road pavements can be destroyed. Besides, aquatic life can be endangered.

Government effort

Governments do provide waste disposal containers where Solid waste is loaded into trucks for onward haulage to landfill sites. However, such sites are seldom subjected to geoscientific and engineering investigations for their suitability or otherwise as waste disposal sites.

Investigation of proposed waste disposal site

Prior to investigating a site for its suitability or otherwise for disposal of solid waste, it must satisfy certain requirements.

(i) It must be remote from major highways, rivers and habitable areas.

(ii)The topography should be fairly flat.

The investigation proper is highly multidisciplinary and comprehensive it starts with the study of the geology of the area.

Surface geophysical surveys can furnish information about the subsurface with special emphasis on the thickness of the overburden (availability of volume for the construction of waste) and groundwater condition. Digging of trial pits and / or sinking of boreholes often furnish information on both geological and Geotechnical engineering properties of subsurface soils and rocks, and the hydrogeology of the location.

Results of in-situ (Site) and Laboratory tests can help in generating the model of the proposed site. The generated model should be similar to the standard model of a sanitary landfill. Prominent among which are that the base of the landfill should be impervious (permeability coefficient of a compacted silty clay that should be less than or equal to 1× 10^-9 m/sec). The base should also be well above the water table. Recommendations should also be made for construction of the landfill such as in-situ compaction and possible use of artificial seals that can prevent seepage of leachate (Liquid component of solid waste)

Monitoring of an active Landfill

It is important to monitor the lateral influence of leachate from a landfill site. Mapping of Pollution plume can help in demarcating the areal influence with a view to determining locations that are safe for digging of water wells and boreholes. The study involves use of geophysical and geochemical methods.

Waste to Wealth

Waste can be converted to organic fertilizers which Lagos State waste management Authority has been exporting to Countries like Ghana. Electricity and gas can also be generated from recycling of solid waste. Scientific Study of an abandoned land-fill site can indicate depth of occurrence of Scrap metals which can be recycled.

Conclusions

Solid waste should be disposed in such a manner that it would have no detrimental impact on the environment.

Flooding and pollution of surface and groundwater should be prevented.

Integrated geoscientific and engineering methods should be utilized as practiced in developed countries of the world.