Evaluation of Boron Removal by Coagulation- Flocculation and Electrocoagulation Bouguerra Wided A* , Moussaoui Khawla A , Ben Khlifa Eya A , Hamrouni Béchir A Faculté des Sciences de Tunis, Département de Chimie, a U. R Traitement et Dessalement des Eaux 2092 Manar II, TUNISIE Abstract - High boron levels in drinking water can be toxic to humans. According to the WHO regulations (2011), the boron concentration should be reduced to less than 2.4 mg L -1 for drinking water. The aim of this study is to investigate the feasibility of coagulation-flocculation and electrocoagulation as a pre-treatment process to remove boron from natural water. Standard jar tests using coagulation and flocculation simulator were carried out to determine the effectiveness of chemical pre- treatment for removal of boron. (MgCl 2 , 6H 2 O) was used as coagulation adjuvant in combination with optimum coagulant dose to observe their differential effects. To optimize the experimental conditions of boron removal, commercial flocculant was used. Afterward the performance of electrocoagulation process to remove boron was investigated by optimizing the experimental conditions, such as pHi, electrolysis time, initial conductivity of the solution ( i), and current density. Experiments were carried out with initial boron concentration of 5 mg L -1 . Keywords— Coagulation; alum; electrocoagulation; aluminium electrode; Boron removal; I. INTRODUCTION Desalination of seawater and brackish water has become increasingly important as a source of water supply to contend with the population burden worldwide. The occurrence of boron which exists mainly in the form of boric acid (H 3 BO 3 ) in water is undesirable. Boron is one of the inorganic constituents that are problematic and difficult to get rid of. The presence of boron in water has two differentiated origins, one of which is natural origin due to the boron in silts present in the aquifer and the other one is the anthropogenic origin, such as wastewater discharge from boron mines and boric acid plants. In order to prevent the environmental problems of high concentration of boron in waters, their boron contents should be removed by a suitable method [1]. Boron is widely distributed in the environment, from natural or anthropogenic sources. It can be found mainly in the form of boric acid or borate salts. When the acid dissociation constant of boric acid (5.81×10 −10 at 25°C; pKa = 9.24) is considered, it can be predicted that H 3 BO 3 is the predominant form at neutral and low pHs whereas BO 3 3− is expected to be present at high pHs. Both forms may exist in equilibrium at a pH range of 7.0–11.5. At physiological pHs, the undissociated form, H 3 BO 3 , is predominant. Boron is an important micronutrient for plants, animals and humans, but it can be toxic at high concentrations. In recent years the use of boron compounds in metallurgy, microelectronics, glass products and in fertilizers has been increasing; so that boron compounds are released into the environment from these sources [2]. High levels of boron are found in seawater (4.7 mg L −1 ), domestic wastewater (0.5–2 mg L −1 ), and regional groundwater (e.g., Italy Cyprus and Greece with boron content up to 8 mg L −1 ). High boron levels in drinking water can be toxic to humans as boron has been shown to cause male reproductive impediments in laboratory animals [3]. The World Health Organization for many years had recommended the drinking water limits for boron as low as 0.5 mg L -1 . Lately, the Expert Group on Guidelines for Desalination recommended that the guideline for boron should be reconsidered in the light of new thinking on the toxicity, as boron levels are quite high in seawater and boron removal is difficult [4, 5]. Therefore, the Drinking Water Quality Committee, at its meeting of 9-13 November 2009, recommended revising the Boron Guideline Value to 2.4 mg L -1 . The revised Guideline Value was incorporated into the Guidelines for Drinking-Water Quality, 4 th Edition, that was published in 2011 [5, 6]. In areas where the shortage of water is a concern, processes have been developed to obtain water from seawater and brackish waters by means of reverse osmosis (RO) processes. These processes present percentages of elimination of salts superior in most cases to 98%. Therefore, Marifias [7] reports the use of RO to eliminate boron, always at high pH, assure that the chemical form of the boron is of borates, presenting, due to the pH, the problem of the deposition on the membranes of other compounds (mainly salts of calcium and magnesium) that involve frequent chemical cleaning. Chemical coagulation followed by sedimentation is a proven technique for the treatment of high suspended solids wastewater especially those formed by the colloidal matters. Research and practical applications have shown that coagulation will lower the pollution load and could generate an adequate water recovery [8–10]. Coagulation is mainly done with inorganic metal salts, e.g. aluminum and ferric sulfates and chlorides which are widely used as coagulants in water and wastewater treatment and in some other applications. Electrochemical technology contributes in many ways to a cleaner environment and covers a very broad range of technology [5, 11, 12]. Electrocoagulation (EC) is an efficient method used for treating various process effluents and investigated as a new technology for boron [5, 12, 13]. 2923 Vol. 3 Issue 2, February - 2014 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 www.ijert.org IJERTV3IS21459