REMOVAL OF HEAVY METALS FROM REFINERY EFFLUENT USING SAWDUST INOCULATED WITH ASPERGILLUS NIGER AND PENICILLIUM SPECIES
CHAPTER ONE
1.0Â Â Â Â Â Â Â Â INTRODUCTION
1.1Â Â Â Â Background of the study
It has long been established that, waste effluents from petroleum refineries are heavily contaminated with a wide range of toxic organic compounds (Zhu et al., 2001; Bako et al., 2002; Vanhamme et al., 2003) and heavy metals (Beddri and Ismail, 2007; Marcus and Ekpete, 2014). The literature is also replete with evidence of the harmful impacts of these toxic pollutants on the environment and human health (Varsha et al., 2010; Mudhoo et al., 2011; Ramzan etal., 2011; Silins and Johan 2011; Tokar, et al., 2011; Marcus et al., 2013; Ho et al., 2014). The known toxic pollutant metals include lead, chromium, cadmium, copper, nickel, zinc, arsenic and mercury (Hamza-Izzeldinet al., 2013). These metal ions are toxic to humans, aquatic flora and fauna. Lead, cadmium and nickel may be accumulated in the human body causing different diseases such as erythrocyte destruction, muscular cramps, renal degradation, pulmonary fibrosis, skeletal deformity, diarrhea, dermatitis and encephalopathy. They also suppress plant and animal life, damage aquatic life and kill microorganisms (Okerentugba and Ezeronye, 2003; Alao et al., 2010).
Many of the conventional treatment technologies such as chemical precipitation, chemical oxidation, solidification, ultrafiltration, flocculation, electrolyte extraction, dilution, sedimentation, evaporation, reverse osmosis, neutralization and membrane separation have been used for removal of metal ions from solution (Yan and Viraraghauan, 2005; Ahluwalia and Goyal, 2007; Amany et al., 2015). However the application of such methods is limited because of economical or technical constraints. The methods have also been reported to be inefficient in the removal of heavy metals from effluent (Bishnoi and Garima, 2004; Iqbal et al., 2005; Otukunefor and Obiukwu, 2005; Ezzouhri etal., 2009).
For these reasons, the past two decades have witnessed continuous and consistent search for efficient, cost effective and eco-friendly means of treating waste and effluents from petroleum related industries prior to their release into the environment (Kapoor et al., 1999; Park et al., 2006; Demirbas, 2008; Khashimova et al., 2008; Farooq et al., 2010). The outcome of such researchestablished adsorption as the most effective and versatile technique for heavy metals removal even at very low concentration (Rao et al., 2010; Dhokpande and Kaware, 2013; Mohammed et al., 2015). However, the high price of adsorbents (usually activated carbon) is the major problem for industrial applications. Biological methods such as biosorptionor bioaccumulation strategies for the removal of metalsions may provide an attractive alternative to existing technologies(Volesky and Holan, 1995; Preetha and Viuthagiri, 2005; Wuyep et al., 2007; Dhankhar and Hooda, 2011).
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REMOVAL OF HEAVY METALS FROM REFINERY EFFLUENT USING SAWDUST INOCULATED WITH ASPERGILLUS NIGER AND PENICILLIUM SPECIES
