Pollution Problems And An Engineering Approach To The Management And Control Of Industrial Effluents

This study investigated the impact of industrial effluent discharges on a selected river in a heavily industrialized community, focusing on both the river’s natural recovery capacity and the treatability of the effluents and receiving water.

The research encompassed a field survey of industrial facilities in the Ado Odo/Otta industrial zone of Ogun State, Nigeria. It involved assessing the physico-chemical, biological, and microbial properties of effluents, as well as their influence on the receiving surface water using established methodologies. Primary data collection included structured questionnaires and interviews to gauge industries’ contributions to water pollution.

To enhance analytical rigor, various scenarios for improving water quality along the studied river were explored. A suite of computer-based hydrogeometric and water quality models, including QUAL2K, was employed. This enabled a detailed analysis of the Atuwara River—a 10.81 km stretch from Owode-Ijako to Iju Water Works—through GPS mapping and regular grab sampling across seven segments, each 0.3 km long.

The study assessed effluent discharges from all industrial sources for priority pollutants like BOD, COD, TDS, TSS, and heavy metals using standard techniques. Effluent samples were compared with pre- and post-discharge river water samples across dry and wet seasons. Model outputs were integrated with GIS to visualize polluted zones, limnographic features, and wetlands within the Atuwara watershed. The most severe effluent scenarios were subject to laboratory-scale treatability tests, employing electro-Fenton alone or followed by Granulated Activated Carbon (GAC) type BBC 945 to mitigate heavy metal contamination.

Findings indicated acidic effluents (pH 5.4 – 6.7) year-round, with particularly high BOD and COD concentrations immediately downstream of discharge points. Dissolved oxygen levels remained low (anoxic) at discharge points but improved downstream, particularly near tributary inflows. The river’s assimilative capacity was notably high due to tributary contributions, though peak BOD discharge scenarios reached 12 metric tonnes per day. Heavy metal levels (cadmium, lead, iron) exceeded FEPA standards across all river sections, indicating severe impairment unsuitable for human consumption without adequate treatment.

Effluent treatment experiments highlighted effective COD removal (over 66%) with electro-Fenton treatment at specified H2O2/Fe2+ ratios, enhanced to 86% with subsequent GAC treatment.

To achieve regulatory water quality standards, the study recommends stringent enforcement of effluent load reductions through mandatory, adequately treated in-house processes at controlled discharge rates by industrial firms.

In summary, the Atuwara River was identified as heavily polluted, necessitating urgent regulatory actions and enhanced industrial practices to restore its water quality and safeguard public health and environmental integrity.