Treatment of Acidic Mine Effluents and Wastewater from Ship Cleaning Facilities by Application of Red Mud

The paper presents a procedure for treating acidic effluent generated during the exploitation and processing of copper ore at the Bor mining complex (Bor-Krivelj-Cerovo) by application of red mud, a waste by-product of the alumina production process at the now-defunct alumina plant in Obrovac, and the application of the generated waste mud to treating wastewater from ship cleaning facilities. The characterisation of wastewater and red mud was carried out, resulting in the determination of optimal conditions for the removal of key indicators from wastewater. The acidic mine wastewater is characterised by a low pH value (3.21), high sulfate concentration (10,830 mg dm-3), high values of iron (921 mg dm-3), manganese (107 mg dm-3), copper (92 mg dm-3) and zinc (59 mg dm-3), whereas the key polluters in the wastewater from ship cleaning facilities include copper (34 mg dm-3), zinc (59 mg dm-3) and paint (11470 PtCo). Considering a high neutralisation and adsorption capacity of red mud, its mixing with mine drainage wastewater in optimal ratios leads to the neutralisation of both waste by-products and the removal of heavy metals from wastewater to below their limit values. Under the optimal removal conditions (pH = 8; contact time = 15 minutes), more than 99.9% of Cr, Mn, Fe, Cu and Zn as well as 65.5% of sulfates were removed. The remaining waste mud can be reused in the treatment of wastewater from ship cleaning facilities which has a high load of anti-fouling paint. A single mud dosage is sufficient for five treatment cycles and has a key indicator removal efficiency rate of over 99%.