Abstract Effect of acid digestion methods on total metal recovery from sludge from water treatment plants in Nigeria was conducted. Sludge samples from four (4) different water treatment plants namely Lower Usuma Dam Water Treatment Plant, Bwari (LUDWTP), Le-Meridien Ibom Hotel and Golf Resort Water Treatment Plant, Uyo (LMWTP), Akwa Ibom State Water Company Water Treatment Plant (AKWTP) and Champion Brewery Water Treatment Plant (CBWTP) were collected and analysed for total metal recovery using Atomic Absorption Spectrophotometer after digestion using two different acid combinations (aqua regia and HNO3/ HClO4 2:1). The results reveal that HNO3/HClO4 extract recorded the highest mean total 16.58 mgkg-1 Zn, 0.40 mgkg-1 Cu and 0.47 mgkg-1 Cd than aqua regia extract in all the fifteen metals analysed. Aqua regia extracts had the highest mean total 61.99 mgkg-1 Ca, 3.60 mgkg-1 K, 29.57 mgkg-1 Mg, 52.19 mgkg-1 Fe, while Co, Cr, Pb, Mn and Na were 0.07, 0.27, 1.47, 19.37 and 12.69 respectively. Aluminium and arsenic levels were not detected in all the four samples extracted with aqua regia and HNO3/HClO4. From the results of this work, aqua regia digestion method is very effective for use in routine monitoring of metals in sludge from water treatment plants in Nigeria.
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