Main, WSEAS World Congress, Malta, September 2008

Plenary Lecture

Arsenic Contamination of Groundwaters in Southeast-Asia and Europe, Mechanisms Inducing its Mobility and Groundwater Treatment

Professor Ioannis A. Katsoyiannis
EAWAG, Swiss Federal Institute for Aquatic Science & Technology
Department of Water Resources & Drinking Water
Ueberlandstr. 133
CH-8600 Duebendorf
Switzerland

Abstract: As the world population increases beyond six billion, one of the most fundamental resources for human survival, clean water, is decreasing. Revised estimates from the World Health Organization (WHO) indicate that 43% of the world population does not have adequate sanitation and 22% do not have clean drinking water. The rising demands for clean water cannot be met by surface water supplies. This has led to increased dependence on groundwater sources in many parts around the world. This increased groundwater utilization has caused several health issues, due to the presence of geogenic toxic pollutants such as arsenic.
In South East Asia (Bangladesh, Vietnam, West Bengal, Nepal, Cambodia) over 50 million people depend on groundwater with arsenic concentrations higher than the local limits of 50 µg/L and over 500 million people might consume water with arsenic over the WHO, USA and EU limits of 10 µg/L. In the USA more than 13 million people, mostly in Western States, consume drinking water with more than 10 µg/L arsenic. In Europe, many regions are affected by elevated arsenic concentrations (Hungary, Romania, Greece, Spain, Finland, Germany).
Large drinking water plants in Northern and Central Europe normally find alternative and arsenic free water resources, or they apply conventional hi-tech removal methods such as coagulation/ filtration, activated alumina and ion exchange, Granular Ferric Hydroxide (GFH) or Bayoxide (E33). Smaller towns, communities and individual users in rural areas often rely on local water resources and removal methods developed for large plants are not applicable because of high operational and capital costs. In addition, these removal units are often too complicated to operate, or their use is limited by the local water composition. In Bangladesh and West Bengal a number of simple treatments has been developed for use (e.g. oxidation of As(III) with chemical oxidants or with sunlight followed by precipitation with naturally present or with added iron- and aluminum salts, removal with zerovalent iron, sorption in prefabricated filters with iron- and aluminum oxide sorbents). Only a few removal methods have received government approval in Bangladesh and most treatment units are still in the test phase.
Alternative removal units designed for the removal of dissolved iron and manganese from groundwater based on biological oxidation, avoiding the use of chemical reagents for pre-oxidation, have been examined. It has been found that when As(III) and As(V) are present in groundwaters, both species can be simultaneously removed by oxidation of As(III), which is accelerated by the presence of indigenous bacteria, and subsequent sorption of As(V) onto the biologically produced freshly precipitated iron or manganese oxides. However, there are still open issues regarding the applicability of these technologies as they present several limitations, especially when iron and manganese are not present or they are present at low concentrations.
To overcome these limitations, treatment units have been developed using Zero Valent Iron (ZVI) as an efficient source of Fe(II), which in the presence of dissolved oxygen mediates the oxidation of As(III) and the produced As(V) can be adsorbed strongly on the forming Hydrous Ferric Oxide (HFO).
This presentation will give a brief overview of the relevant processes occurring during treatment under aerated conditions, corresponding to pump and treat technologies. It shows that lot of work has been done but still more work is needed to fully understand the important reaction pathways and to further optimize and expand the range of arsenic removal methods. One of the major challenges is the large variability in the concentrations of the most important water constituents that affect the performance and operation time of arsenic removal units.

Brief Biography of the Speaker: I studied chemistry in the Aristotle University of Thessaloniki and did a Master of Science on Environmental Pollution Control Management in Edinburgh, Scotland. I did my Ph.D. in the Aristotle University of Thessaloniki, in the Department of Chemistry, under the supervision of Professor Anastasios Zouboulis. The subject of my Ph.D. was in the field of water treatment and in particular in the field of groundwater treatment for the removal of inorganic contaminants. I worked extensively with the biological removal of iron and manganese from groundwaters, whereas the core of my Ph.D. was the study of arsenic removal. I examined and applied several methods physicochemical, biological and combinations of them and the results were published in international scientific peer reviewed journals and have been already applied in the field, i.e., a treatment unit installed in Northern Greece.
During my Ph.D., I managed to obtain twice a short scholarship from the German Academic Exchange Service (DAAD). I had the opportunity to perform research in the Technical University of Berlin under the supervision of Professor M. Jekel in cooperation with the German Federal Environmental Agency (Umweltbundesamt) under the supervision of Prof. Andreas Grohmann. In my research career, I was also involved in other projects such as the removal of humic acids from stabilized landfill leachates applying different removal techniques such as flotation or coagulation and the use of microfiltartion assisted coagulation for removal of inorganic contaminants. In 2002, I received the MESAEP Award from the Mediterranean Scientific Association of Environmental Protection and in 2006 the Chemistry AWARD from the Empirikion Foundation in Greece.
After the completion of my Ph.D. I received a fellowship from the Alexander von Humboldt Foundation in Germany, where I did a post doc on the aquatic chemistry of uranium and its removal from groundwaters, in the Technical University of Berlin with Professor M. Jekel. Following my Post Doc in Berlin, I applied together with Dr. Stephan Hug from the Swiss Federal Institute of Aquatic Science & Technology (Eawag) for a Marie Curie Individual Intra European Fellowship, which was approved and therefore, since January 2006 I joined Eawag, the Swiss Federal Institute for Aquatic Science & Technology.
The results of my work have been published in international peer reviewed journals, while I have participated in several international conferences, workshops and summer schools and I have written two contributions for the water Encyclopedia of Wiley.