Column studies to assess the effects of climate variables on redox processes during riverbank filtration.

Riverbank filtration is an established technique used world-wide to produce clean drinking water in a reliable and cost-efficient way. This practice is, however, facing new challenges posed by climate change, as already observed during past heat waves with the local occurrence of anoxic conditions. In this study we investigated the effect of direct (temperature) and indirect (dissolved organic matter (DOM) concentration and composition, flow rate) climate change variables on redox processes (aerobic respiration, denitrification and Mn(III/IV)/Fe(III) reduction) by means of column experiments.

NOM degradation during river infiltration: effects of the climate variables temperature and discharge.

Most peri-alpine shallow aquifers fed by rivers are oxic and the drinking water derived by riverbank filtration is generally of excellent quality. However, observations during past heat waves suggest that water quality may be affected by climate change due to effects on redox processes such as aerobic respiration, denitrification, reductive dissolution of manganese(III/IV)- and iron(III)(hydr)oxides that occur during river infiltration. To assess the dependence of these redox processes on the climate-related variables temperature and discharge, we performed periodic and targeted (summer and winter) field sampling campaigns at the Thur River, Switzerland, and laboratory column experiments simulating the field conditions.

Effect of iron and phosphate on bacterial cyanide formation determined by methemoglobin in two-dimensional gradient microcultivations.

Cyanide formation by microorganisms is typically observed during early stationary growth phase and is facilitated by the presence of iron(III) and inorganic phosphate. Extracellular free cyanide in aqueous solutions might readily react with methemoglobin added and can be determined by UV/VIS spectroscopy. As alternative to existing methods, this provided the basis for an analytical method which has not been used previously for the determination of cyanide in bacterial cultivations.