Simultaneous Drinking Water Winning and Treatment by In-Situ-Bioreactors
Meyer, C.1, Krauß, M.1, Steinmetz, H.1
1 Institute for Sanitary Engineering, Water Quality and Solid Waste Management,
University of Stuttgart, Bandtaele 2, 70569 Stuttgart, Germany
(free)
Natural groundwater is an important resource for drinking water, but in the majority of cases, it contains high quantities of iron, manganese and in some cases arsenic. Without treatment such waters cannot be used for drinking or process water purposes.
By means of in-situ-bioreactor technology, the groundwater is simultaneously won and treated. In-situ bioreactors provide both operational and economical advantages.
In-situ bioreactors are capable of effectively removing iron, manganese and arsenic from raw water. Shortly after the start-up of the treatment the iron concentrations met the German drinking water standards and the American National Primary Drinking Water Regulations standards (MCL, SMCL, U.S. EPA) for drinking water.
Through inoculating an in-situ bioreactor with adapted micro-organisms the initial manganese removal adjustment period could be reduced significantly.
By microbiological methods various iron and manganese oxidising bacteria, e.g. related to the families Comamonadaceae, Hyphomicrobiaceae, Rhizobiaceae and others could be identified in undisturbed soil samples from the biologically active reaction zone.
Low-tech in-situ bioreactors for the removal of arsenic from drinking water were designed, and tested in West Bengal (India), an arsenic hot spot. Depending on the hydrogeological/raw water conditions the arsenic concentration in the treated water met the Indian standard and the WHO guideline value relatively quickly.
Keywords
groundwater; subterranean groundwater treatment; iron; manganese; arsenic; drinking water treatment; biotechnology
Introduction
Natural groundwater is an important resource for drinking water. Very often iron (Fe), manganese (Mn) and in some cases arsenic (As), occur naturally in the borehole (raw) water. Whereas elevated arsenic concentrations (WHO guideline value: 10 µg/L) can imply a significant health hazard, iron and manganese are normally not considered to be a health concern. Particular aesthetic and operational problems noted for iron and manganese include the staining of surfaces and clothes and deposits and clogging in the water distribution network, respectively.
Various treatment processes for the removal of iron, manganese and arsenic exist, e.g. coagulation/filtration, ion exchange, reverse osmosis, adsorption to activated alumina/ferric hydroxide for arsenic removal and oxidation/coagulation/rapid granular bed filtration for iron/manganese removal.
The in-situ-bioreactor technology represents a different approach. The groundwater is simultaneously won and treated, which leads to a number of competitive advantages against conventional iron, manganese and arsenic removal technologies:
less above-ground facilities are needed (little land consumption) as the treatment processes predominantly take place in the aquifer itself (subterranean reactor)
no need for water treatment chemicals
no production of potable water filtration sludge
no clogging of wells with iron or manganese hydroxides/oxides
the technology is arbitrarily scalable from small (household) drinking water supply units to large-scale waterworks.
