Removal of Heavy Metals from Sludge by Soil Washing Method

Experiments were performed to study the removal of heavy metals from waste water treatment plant sludge by soil washing method. Increasing release and accumulation of heavy metals in soil by industrial and other human activities pose serious threat to the functioning of the components of ecosystems, viz., biota, air, water and soil. Heavy metals are known to cause significant environmental damage and human health problems due to their mobility and solubility. Soil washing technology is the most efficient, easy to operate and simple method for treatment of soils contaminated with heavy metals. Soil washing is one of the most suitable in-situ/ ex-situ remediation method in removing heavy metals .To increase the performance of soil washing various chemicals can be added, such as Ethylenediaminetetraacetic acid disodium salt (Na2EDTA) solution were used as extractants. Sludge samples were subjected to chelant extraction using a solution of disodium salt of Ethylenediaminetetraacetic acid (Na2EDTA). In this paper an attempt has made to evaluate soil washing technology for heavy metal removal i.e zinc from the contaminated sludge by optimizing the parameters like reaction time and EDTA concentration. Zinc removal efficiency was found to be dependent on contact time, EDTA concentration and their initial concentrations in contaminated soils. The results showed that removal efficiency of zinc were maximum using EDTA (0.1M) is 40-50%.This paper also describes the development of a bench scale model and results obtained from these bench scale tests. These test showed that the new soil washing process can remove the heavy metals from sludge economically and efficiently. The experiment was carried out to study the removal of heavy metals from sludge obtained from waste water treatment plant by soil washing method for land application.