ARSENIC REMOVAL FROM GROUNDWATER BY COAGULATION PROCESS: PERFORMANCE AND LIMITATIONS INFLUENCED BY THE GROUNDWATER SOURCES CHEMISTRY USED FOR DRINKING WATER PURPOSE IN THE WEST REGION OF ROMANIA

Arsenic (As) contaminated groundwater is a critical issue of concern, in view of its toxicity through drinking water and health impacts on the human body. In this regard, the World Health Organization (WHO, 1993) has recommended 10 ?g/L for dissolved As concentration in water as standard value for drinking purposes. Special attention should be paid to the monitoring the quality of the groundwater, the chemistry and composition of arsenic-contaminated water are the major factors, determining the applied technologies for removal of arsenic. The coagulation-flocculation process is well known as physico-chemical technique for As removal, which provides high removal efficiency, even at high concentrations of As(V). This method have many advantages: high stability, low cost, simple operation and fast sedimentation. This paper examines the current scenario of arsenic contamination of groundwater in the West Region of Romania, and evaluate the As removal performances and limitation of different coagulants used, their operating conditions, properties, and efficiencies. The coagulation experiments were conducted through the Jar test, which simulates three steps including coagulation, flocculation, and settling. The coagulants tested comparatively were ferric and aluminum-based coagulants, respectively ferric chloride, ferric sulfate, aluminum sulfate and polyaluminum chloride. Better coagulating performance of the ferric salts compared with the aluminum salts has been confirmed due to their higher density of adsorption.