Heavy metals remediation of water using plant and lignocellulosic agrowastes

Abstract

Metals in the environment arise from natural sources or directly or indirectly from human activities such as rapid industrialization, urbanization, and anthropogenic sources, threatening the environment and human health (Nriagu 1979). Mining and metallurgical activities produce wastewaters that can be considered as the major source of heavy metal contamination of natural waters (Schalcsha and Ahumada 1998; Reddad et al. 2002a). In the United States alone, more than 50,000 metal-contaminated sites await reme diation, many of them Superfund sites (Ensley 2000). They are potential hazards to aquatic, animal, and human life because of their toxicity and bioaccumulative and nonbiodegradable nature (Zuane 1990). Nonessential metals such as Hg, Cd, Cr, Pb, As, and Sb are toxic in their chemically combined forms as well as the elemental form (Manahan 1993).Acute metal poisoning in humans causes severe dysfunction in the renal, reproductive, and nervous systems, and chronic exposures even at low concentrations in the environment can prove to be harmful to human health (Wyatt et al. 1998). In addition, heavy metals that are discharged from a wide variety of industries such as electroplating, metal finishing, leather tanning, chrome preparation, production of batteries,phosphate fertilizers,pigments,stabilizers,and alloys to the aquatic environment have adverse impacts on aquatic species because they are conserved pollutants that are not subject to bacterial attack or other breakdown and remain as permanent additions to the marine environment (MacCarthy et al. 1995; El-Nady and Atta 1996). They are dangerous to aquatic animals because they tend to bioaccumulate and cause physiological defects and histopathological manifestations in tissues, resulting in reduced reproduction (Gardner 1975; Cutter 1991; Joseph et al. 2002; Krishnani et al. 2003a). Once mobile in the environment in ionic form, they find their way into the human body through drinking water, food, and air. There is a reasonable chance of having a fair amount of toxic metals in the body if a person has eaten fish regularly, has amalgam fillings, has received vaccinations, has drunk contaminated water, or been involved in industrial or agricultural work or pharmaceutical manufacturing.