Desalination 197 (2006) 247–261 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved *Corresponding author. Treatment of industrial effluents using fortified soil-clay N.A. Oladoja a *, C.M.A. Ademoroti b , I.O. Asia c a Department of Chemistry, Adekunle Ajasin University, Akungba-Akoko, Nigeria Tel. +234 (80) 55438642; email: bioladoja@yahoo.com b Department of Chemistry, University of Benin, Benin City, Nigeria c Department of Chemistry, Ambrose Alli University, Ekpoma, Nigeria Received 5 August 2005; accepted 5 January 2006 Abstract The ability of some tropical soil-clays in industrial wastewater treatment was investigated in this study. The soil-clays were characterized by studying the mineralogical and geochemical characteristics using X-ray diffractometer and atomic absorption spectrophotometer (AAS), respectively. Performance efficiency studies were conducted to determine the best combination ratio of soil-clay/pebbles. Soil-clay fortified with pebbles in the ratio 3:1 gave the optimum water purification while combination ratio 1:3 gave the least. The flow rate studies showed that the wastewater had a longer residence time in non-fortified soil-clay than in fortified soil-clay. The fortified soil-clays were used in the treatment of wastewater from different sources, viz. brewery, textile and natural rubber processing factories. Two modes of treatment methods were adopted: single and double column treatment (SCT and DCT). The two modes performed satisfactorily but effluents from DCT had better quality. The effects of repeated usage on the performance efficiency of the fortified column were studied and the results showed a decrease of pH, TS and DO and an increase of COD when monitored over time. Keywords: Fortified; Effluent; Column; Soil–clay; Industrial; Treatment 1. Introduction In the modern world, progress and prosperity go pari-passu with a reliable water supply that is adequate in both quality and quantity. This accounts for the clustering of manufacturing companies around important rivers due to the pertinence of water to their operations. Industrial use accounts for around one-quarter of worldwide freshwater demand [1]. Such demand has led to increasingly stringent environmental legislation and associated escalating costs of water supply and discharge. Wastewater reuse has been made possible through the development of different wastewater treatment technologies. An array of centralized wastewater treatment technologies, e.g. trickling filters, activated sludge, rotary