THE EFFECT OF SEWAGE EFFLUENT ON THE PERMEABILITY OF SOIL
CHAPTER ONE
INTRODUCTION
Objectives of the Study
Most ancient structures collapse, mainly due to lack of knowledge on permeability. Properties such as permeability help an engineer, to determine the suitability of soil for some engineering works. Hence, modern civil engineering works allows for site investigation, which includes the determination of the permeability relative to the soil which would be used for the work. The main aims of this research are.
· To determine the maximum dry density (MDD) of soil, thus increasing its shear strength and bearing capacity.
· To determine the rate of seepage of water through a given soil sample.
· To determine how permeability of soil is affected by sewage effluent of different levels of pollutal strength.
Scope of the Study
This research will be carried out using soil sample, collected by digging one meter below the ground level, from a farm land located nearby the junior staff quarters. The sewage effluent will be collected from the university of Nigeria treatment tank, by varying the quantity of sewage used.
DEFINITION OF TERMS:
PERMEABILITY: This is the property of soil which permit flow of water through it’s inter connecting voids. Permeability is an important engineering property, which governs the rate of flow of aquifer. Hence, permeability in its simplest term is the ease with which water can flow through soil.
Sewage effluent: Sewage is the wastewater of a community consisting of human excreta, urine and sullage. Solid forms a very small percentage (0.1%) of fresh sewage. Sewage may contain pathogenic organisms, organics and nutrients. Hence, sewage must be treated before discharge in order to prevent pollution of surface and underground water source. Sewage exerts biological oxygen demand in rivers, which depletes oxygen. Besides, being rich in nutrients (mainly nitrogen and phosphorus), sewage causes in receiving water algal bloom and autrophication. Generally, supplying it with oxygen treats wastewater, so that bacteria may utilize the waste as food.
Compaction: Compaction means processing the soil particle close to each other by mechanical methods. Air during compaction, is expelled from the void space in the soil mass and, therefore, the mass density is increased. Compaction of soil mass is done to improve its engineering properties. Compaction generally increases the shear strength of the soil, and hence the stability and bearing capacity. It is also useful in reducing the compressibility and permeability of the soil. Compaction of soil is required for the construction of earth damage canal embankments, highways, runaway, and in many other engineering applications.
Failure: Dense sand shows initially a volume decrease in a drained test, but as the strain increases, the volume starts increasing. The loose sand shows a volume decrease throughout. In case of loose sand, the specimen bulges and ultimately fails by sliding simultaneously on numerous planes. The failure in this case is known as brittle failure.