Contaminants in selected industrial effluents and their effect on groundwater quality near factories in two cities of South East Nigeria

Effluents from vegetable oil mill, paper mill and paint factories in Aba and Umuahia, South East Nigeria were analysed for contaminants and dissolved minerals. Water from boreholes within a 50m radius of the factories was also subjected to quality assessment. Paper and paint industry effluents contained the highest lead (21.6 mg/L), copper (27.5 mg/L), zinc (25.8 mg/L), cadmium (23.8 mg/L), chromium (31.7 mg/L) chloride (1600mg/L), and dissolved nitrate (43.9 mg/L) from vegetable oil mill were all above limits allowed for factory effluents. Fe levels in all three industrial effluents (0.6 – 6.4 mg/L) exceeded allowed limits. Water from boreholes in the vicinity of the three factories was acidic, with pH ranging from 4.8 – 5.6. Borehole water near the paint and paper factory had significantly elevated levels of dissolved nitrate (16. 83 and 22.3 mg/L respectively), above WHO limit allowed for drinking water in the long term. The discharge of paper mill effluents also led to elevated Cl (363 mg/L), Ca (113 mg/L), Mg (12 mg/L) and sulphate (349 mg/L) exceeding allowable limits in groundwater The heavy metal levels in all the boreholes analysed were however within safe limits.