This study demonstrates that a lean panel of DO–BOD–COD can deliver credible, decision-relevant evidence on organic matter in the study metropolis. Across all sources, oxygen-demand metrics were modest DO (5 mg L⁻¹), BOD (1.8 mg L⁻¹), COD (4.6 mg L⁻¹) and the mean BOD/COD (0.4) indicates a mixture of biodegradable and refractory organics typical of diffuse domestic inputs rather than strong industrial discharge. Kruskal–Wallis tests detected no significant differences in DO, BOD, or COD among wells, boreholes, and rivers, implying a broadly similar organic matter pressure city wide. The positive correlations among the indicators (DO–BOD, DO–COD, BOD–COD) show that they co-vary at the spatial scale sampled; together with the BOD/COD ratio, they provide a compact signal of water-quality change suitable for routine surveillance. Comparison study with other conducted elsewhere in Nigeria, indicates this study area exhibits lower to mid-range organic loads relative to several documented hotspots, yet a few wells with elevated COD but modest BOD point to refractory constituents (e.g., detergents/hydrocarbons) that warrant targeted follow-up
Olatunji et al. (Tue,) studied this question.