October 2014, Volume 5, No.5 International Journal of Chemical and Environmental Engineering Effect of Dewatering aid Dosage in Electroforced Sedimentation Md. Monjurul Alam a,* ; Mohammed Saedi Jami a ; Md Zahangir Alam a ; Masashi Iwata b a Department of Biotechnology Engineering, Faculty of Engineering, International Islamic University Malaysia, Kuala Lumpur, Malaysia; b Department of Chemical Engineering, Graduate School of Engineering, Osaka Prefecture University, Sakai, Japan * Corresponding Author E-mail:m_alam2002@yahoo.com Abstract: Nowadays wastewater treatment plants are producing huge amount of sludge. The water content of the traditionally dewatered sludge, resulting from drying beds, centrifuges, vacuum filters, screw press filters and pressure filters, remains a critical factor affecting the choice of transportation vehicles, transportation costs, and suitability of sludge for incineration. The objective of this study is to investigate the role of polyacrylamide dose and constant current density on the electroforced sedimentation of sludge dewatering process. Zinc Oxide slurry was used as model sludge. Electroforced sedimentation experiments of zinc oxide suspended in aqueous media with and without polyacrylamide were carried out under various constant electric current densities. It was observed that at the same constant electric current density, the voltage difference was decreasing with the increase of polyacrylamide dose. Moreover, the highest sedimentation rate was attributed at 1.5% polyacrylamide in electroforced sedimentation of zinc oxide slurry under different constant current densities. Keywords: Electroforced Sedimentation; Dewatering; Zinc Oxide; Constant Current; Polyacrylamide. 1. Introduction Sludge produced from wastewater treatment plant comprises a significant quantity of water. In Malaysia, about 3 million metric tons of sewage dry sludge is produced annually and it has been estimated that the amount will be 7 million metric tons in the year of 2020 [1]. The annual sewage sludge management cost in Malaysia is about US$ 330 million [2]. The treated- sewage sludge is normally either being disposed at landfills or being burned in incinerators [3]. Sludge dewatering is mandatory before transporting sludge to composting, incinerators, landfill or reuse as fertilizer. The application of mechanical methods for sludge dewatering is not enough as it cannot drive the interstitial water through the very narrow pore spaces potentially; therefore further treatment is necessary [4]. Sludge treatment and disposal is representing about 50% of the current operating costs of a wastewater treatment plant [5]. Application of electric field in sludge dewatering processes can greatly improve dewatering efficiency [6] and shows a promising future for the wastewater treatment industry. In elecroforced sedimentation, the separation of liquid from a solid-liquid mixture is achieved between two electrodes. Its principal use would be in reducing water content in environmental sludge and biosolids, thereby reducing the volumes to be disposed through landfills, incineration or other means. In electroforced sedimentation with moderate electric field strength, the moisture of a solid-liquid mixture remains unchanged at the surface of the sediment, while it decreases drastically near the bottom of the sedimentation column. This fact is widely known; to date however, due to paucity of analytical method, it has not been successfully explained. Previously, some works which were related with electroforced sedimentation were done [7]. In our previous report, the solution of the basic differential equation that describes the progress of an electro-osmotic dewatering was presented [8]. The poor dewaterability phenomena of sludge are well known. For the reduction of water content, sludge conditioning by polymer addition is usually employed to increase the dewaterability of sludge [9]. Sludge conditioning is done mainly for enhancing the efficiency of a solid-liquid separation in mechanical dewatering processes such as centrifuge, diaphragm filter presses, and vacuum filter. In addition, the addition of polyelectrolyte provides an opposite excess charge in the liquid phase to balance the surface charge of the sludge particle, which improves the efficiency of the applied voltage gradient responsible for the electroosmotic flow [10]. However, the effectiveness of sludge dewatering depends on the polymer dosage and characteristics along with the characteristics of the sludge.