Development of a Water Treatment Plant for Arsenic Removal Based On the Zero-Valent Iron Technology

ELIANA BERARDOZZI; F. S. GARCÍA EINSCHLAG

Arsenic: Risks of Exposure, Behavior in the Environment and Toxicology

Nova Science Publishers

Lugar: New York; Año: 2017;

Arsenic (As) strongly limits water potability due to its high toxicity. The Chaco-Pampeana plain is one of the regions worldwide recognized for its high arsenic content in groundwater and the involved area covers about 106 km2 in Argentina. Arsenic levels in groundwater above 100 μg / l have been frequently reported. For this reason is fundamental to look for efficient and inexpensive technical solutions for obtaining arsenic-free drinking water.In the present work a three-module continuous plant design, capable of deliver up to 1 m3/day of arsenic-free drinking water, is described. The system, whose first and main stage is a Zero-Valent Iron (ZVI) reactive bed, is simple, easy to use, was designed to respond small communities? needs and can be adapted for groundwater with different physicochemical characteristics.Arsenic removal by ZVI-based technologies is related to the corrosion products generated by metallic iron oxidation and involves different mechanisms, including adsorption, surface complexation, surface precipitation and co-precipitation. Iron corrosion rates depend on both the operating conditions and the ZVI source used. Therefore, the effects of changing the main operational variables, of columns packed with iron wool, were analyzed in order to select the most favorable settings.In addition, the application of this technique in many cases is limited by reactivity losses and reductions of hydraulic conductivity due to the accumulation of corrosion products. These problems arise due to the formation a thick layer of iron oxides onto ZVI surface, especially in natural waters with relatively high dissolved oxygen contents. Consequently, the hydraulic behavior of the designed plant was studied throughout the operation period. In addition, stimulus response tests were carried out periodically to determine the residence time distribution along the reactive column. The results obtained show that the lifespan of the plant may be predicted by taking in to account both the main chemical processes involved and the fluid dynamic properties of the bed.