Methods for treating acid groundwater results and evaluation of long-term tests

Abstract

Acid groundwater can corrode plumbing systems and solubilize metals in the soil or in the plumbing systems. Since the soluble forms of some metals are toxic, concerns regarding the effects of groundwater acidification on human health have been raised. A number of new methods for treating acidified groundwater have been developed and tested during the last decade. In addition conventional filter devices have been tested and evaluated. Seven methods of in situ alkalization, i.e. treatment of the soil around the well with an alkalizer, have been tested for 1–8 years. These methods involve the application of limestone or slaked lime in the recharge area of the well or in/near the well. Target values set for the tests were: pH>6,5 and alkalinity >60 mg/l. Almost all of these methods have led to improvements in water quality, but in some cases target values were not reached. Most of the treatments have resulted in significant reductions in iron and aluminium contents in drinking water. Eight types of more conventional devices for processing acidified well water have been tested for a couple of years. These de-acidification filters are installed indoors or in some cases inside the well. The majority of them performed well, providing acceptable values of pH and alkalinity under normal water flows. However,after periods of more intense water flushing, some of the filters showed a decreased capacity to neutralize the water. Inexpensive types of equipment, e.g. some of the filters placed inside the well, performed just as well as the more expensive types.