8. Conclusion
Over the past two decades, environmental regulations have become more stringent, requiring an improved quality of treated effluent. In recent years, a wide range of treatment technologies such as chemical precipitation, adsorption, membrane filtration, electrodialysis, and photocatalysis, have been developed for heavy metal removal from contaminated wastewater. It is evident from the literature survey of 94 articles (1999–2008) that: lime precipitation has been found as one of the most effective conventional means to treat inorganic effluent with a metal concentration higher than 1000 mg/L; new adsorbents and membrane filtration are the most frequently studied and widely applied for the treatment of the heavy metal-contaminated wastewater; photocatalysis is a promising innovative technique for a clean and efficient treatment.
Although many techniques can be employed for the treatment of wastewater laden with heavy metals, it is important to note that the selection of the most suitable treatment for metal-contaminated wastewater depends on some basic parameters such as pH, initial metal concentration, the overall treatment performance compared to other technologies, environmental impact as well as economics parameter such as the capital investment and operational costs. Finally, technical applicability, plant simplicity and cost-effectiveness are the key factors that play major roles in the selection of the most suitable treatment system for inorganic effluent. All the factors mentioned above should be taken into consideration in selecting the most effective and inexpensive treatment in order to protect the environment.