Geogenic Contamination and Technologies for Safe Drinking Water Supply

Abstract

Arsenic and fluoride are the most widespread geogenic source of contaminants in groundwater affecting the health of millions of people worldwide including India. Geogenic contaminants in groundwater are due to the resulting geochemical changes in the aquifer material – e.g. high concentrations of the contaminant in the rock matrix, dissolving during water-rock interaction – or occur due to environmental conditions such as an arid climate or reducing conditions in the aquifer that facilitates the contaminant to occur in a more mobile state.

In India, approximately 50 million people from seven states in the Ganges-Brahmaputra fluvial plains and about 66.62 million people from 19 states spread over the country have been exposed to drinking arsenic- and fluoride-contaminated groundwater, respectively, in excess to 50 μg/L and 1.5 mg/l. The fluvial plains of arsenic-contaminated groundwater representing Holocene aquifers of recent alluvial sediments have the routes originated from the Himalayan region. The fluoride-contaminated groundwater represents aquifers containing fluorine-bearing minerals. Over the years, because of inadequate surface water-based drinking and irrigation water infrastructural facilities, there has been phenomenal growth of groundwater withdrawal structures, which made problem-resolving issues more complicated by a number of unknown factors. There is no rationale to believe that the growth of groundwater exploitations is going to slow down. Therefore, neither the threat of groundwater contamination from geogenic sources can be overlooked nor the exploitation of groundwater can be reduced.

Although some degrees of success to provide arsenic and fluoride-safe groundwater in some of the affected areas have been achieved by devising point-of-use removal technologies, but the source being the aquifer materials, it is essentially required to search out methods to bring back stability in the geochemical processes of dissolving aquifer materials by focusing more on devising in situ remediation techniques. Ex situ treatment of contaminated groundwater is not a sustainable solution which possibly may exaggerate the problem in the long run. Therefore, we ought to search alternate approach, e.g. in situ remediation of contaminated aquifer, or stop using contaminated aquifer and explore possibility of using most young-aged water in the aquifer or safe deep aquifer or adopt conjunctive use of surface and groundwater including practices of managed aquifer recharge (MAR) and bank filtration technique for supply of safe drinking water without causing harm to the natural water systems.

The chapter is focused to give an insight on hydrogeological and geochemical processes associated with the attribution of contaminants, particularly arsenic and fluoride, to help conceive possible conservation and remedial measures, which are sustainable and effective to reduce the in situ problem. The paper also suggests use of some natural treatment techniques for supply of drinking water to the people in the arsenic- and fluoride-contaminated areas.