Author(s) :

S. A. Ngah, T. K. S. Abam.

Volume/Issue :

Abstract :

For this study, 57 groundwater samples from deep boreholes, (150- 450m) were analysed with a view to identifying major quality issues and their distribution contrary to pervious studies that were concerned with groundwater from shallow boreholes, less than 150 m in depth. The boreholes were scattered in 5 geomorphologic zones in the Niger Delta. The results revealed that three parameters namely, pH, Cl- and Fe2+ stood out as constituting major groundwater quality issues even in deep aquifers. Values of pH range from 3.8 – 8.4 with 62% of the samples having values outside the NIS 554 permissible limits of 6.5 – 8.5. Slightly acidic groundwater is prevalent in the eastern part of the area including Port Harcourt. All the samples analysed indicated that values for iron ranged from 0.02 – 5.6mg/l with 71% of the samples containing iron in excess of 0.3mg/l which is NIS 554 highest permissible limit. The high iron concentrations occurred in boreholes drilled in the freshwater swamp/meander belt region. Chloride values vary from 5.6 -710mg/l with 18% of the samples showing Cl- concentration in excess of 250mg/l recommended by NIS 554 as maximum permissible concentration in drinking water supplies. Chloride concentration is high particularly in the coastal areas and parts of Port Harcourt city bordering saltwater creeks and tidal channels which have influent relationship with the local groundwater table. Most other parameters fall within NIS 554 limits of acceptability. The study clearly showed that groundwater from even deep aquifers needs to be treated to correct the pH, Cl- and Fe2+ concentration before it can meet NIS 554 standards for drinking water supplies.

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