Groundwater forms a very important part of the water supply chain and its quality can be
affected by improperly constructed septic tanks used by homeowners in peri-urban locations
such as Abeokuta in recent times. Sixty groundwater samples collected from hand-dug wells
≤15m from septic tanks were analysed for physicochemical and bacteriological parameters
using standard procedures. Results were integrated with multivariate and hydrogeochemical
analyses to assess the effect improperly built septic tanks have on groundwater quality around
the Federal University of Agriculture, Abeokuta. The range of values for the measured
parameters include: pH (6.26 – 8.66), EC (83 – 1035 μS cm-1), TDS (42 – 621 mg L-1), Mg2+
(2 – 60 mg L-1), NO3
-
(5.09 – 17 mg L-1), Fe (-.04 – 5.32 mg L-1), BOD (0.1 – 13.2) and E.
Coli (ND – 41×10 cfu mL-1). The abundance of major ions are in the order Ca2+˃Mg2+˃K+˃
Na+ and Cl- ˃SO4
2- >HCO3
- >NO3
- ˃PO4
2-. The piper trilinear plot shows that the dominant
hydrochemical facies in the study area is the Ca2+– Cl- type.Etc...