Impacts of septic tank systems on ground water quality in high water table terrain: A case study of Lokoja

Abstract

This research examined the impacts of septic tank systems on ground water quality in high water table terrain using Lokoja as a case study. Eight shallow wells were chosen (four from each area) from two areas of Lokoja namely Adankolo and Gadumo. The distances of the wells from the septic tanks as well as their depths were measured. Water samples were collected from these wells and were subjected to physical, chemical and bacteriological analysis using series of apparatus and reagents and standard quantitative method for bacteriological examinations. Physical parameters including colour, turbidity, electrical conductivity, total dissolved solids (TDS) and pH were analysed as well as chemical parameters including nitrate, calcium, chloride, total hardness, total alkalinity, dissolved oxygen and phosphate. Bacteriological test included coliform count and E-coli count. The results were compared with World Health Organization (WHO) and National Agency for Food, Drugs Administration and Control (NAFDAC) Standards. Correlation and regression as well as analysis of variance (ANOVA) were used to determine if relationship exist between the parameters and distances of wells from septic tanks, the strength of the relationship and if significant difference exist between parameters and distance and between parameters from the two areas. It was noted that siting septic systems near or very close to shallow wells have adverse effects on the water quality from these shallow wells because almost all the physical and chemical parameters were higher than WHO guide level standard recommended for drinking water as they correlated with distance. The viable coliform count per 100ml for the well points (samples) also was above WHO limits. This could lead to water borne disease. There was correlation between parameters and distance in some samples, in some others there was significant difference and the samples from the two areas (Adankolo and Gadumo) are the same.