Cadmium is frequently used and is extremely toxic in relatively low dosages and is one of the principal heavy metals that is responsible for causing kidney damage, high blood pressure, renal disorder, destruction of red blood Cells and bone fracture. Permissible limit to discharge in the inland surface water is 2.0 mg/l, discharge in public sewers is 1.0 mg/l and drinking water is 0.01 mg/l. Adsorption is the only user-friendly technique for the removal of heavy metal. We have developed an ANN model for prediction of percentage removal of Cd(II). A multilayer perceptron with a single hidden layer has been learnt separately by three different algorithms: Backpropagation, Levenberg-Marquardt and Scaled Conjugate Gradient algorithms for analysis purpose. Optimization for each one of the four standard transfer functions (in a single hidden layer) has been carried out in all three cases. The ANN model with Backpropagation algorithm, with the second transfer function and 25 processing elements gives the best predictability of the outlet concentration.
TopIntroduction
The presence of heavy metals in the environment is a major concern as they are toxic in nature. Heavy metal pollutants are non-biodegradable hence environmentally persistent. Heavy metal exists in environment as natural components, and also their concentration has increased in the last century due to industrial revolution after World War II (Nriagu, 1979). As the heavy metals are non-biodegradable in nature, they are accumulated in the food chain via water–plants–animals–humans (Sciban & Klasnja, 2003). Hence the presence of heavy metal ions in water bodies, groundwater and soils from industrial waste water can pose a significant threat to ecological systems and also human health (Sen et al. 2002). For the protection of public health the heave metals removal from wastewater and water bodies are necessary. Heavy metal contamination exists in aqueous waste streams of many industries, such as metal plating facilities, mining operations and tanneries etc. Hence a cost-effective treatment for metals-contaminated wastewater is required, as environmental laws become stringent (Singha & Das, 2012, 2013).
Cd(II) is non-biodegradable and have great environmental impact for its presence in wastewater (Brower et al., 1997; Cay et al., 2004). Cadmium is introduced into the water bodies from different industrial activities like metal mining, plating, cadmium–nickel batteries, smelting, phosphate fertilizers, alloy industries pigments, stabilizers and sewage sludge etc. It is observed that the average Cd(II) concentration from metal plating industries are nearly 15–20 mg/l, and as high as 1000 mg/l concentration in lead mine acid drainage. The harmful effects of Cd(II) include acute and chronic metabolic diseases like testicular atrophy, disorders, renal damage, hypertension, emphysema and itai–itai disease, (Zhou et al. 1993; Chakravarti et al. 1995, Naiya et al. 2009a). Due to toxicity, the recommended maximum tolerance intake of Cd(II) by IS 10,500 for discharge in inland surface water and public sewers are 2.0 and 1.0 mg/l, respectively (IS 10500 1992, CPCB, 1995). The tolerance limits for heavy metal concentration in potable water and discharge into inland surface waters is shown in Table 1 (IS 10500 1992, EPA, WHO).
Table 1. Tolerance limits for heavy metal concentration in drinking water and discharge into inland surface water
| IS 10500 1992 | EPA | WHO |
| Drinking Water (mg/L) | Discharge in Inland Surface Water (mg/L) | Discharge in Public Sewers (mg/L) | Drinking Water (mg/L) | Drinking Water (mg/L) |
| 0.01 | 2.00 | 1.00 | 0.005 | 0.003 |