Elevated manganese concentrations in groundwater wells after longtime abstraction with bank filtration: developing and testing of a sorption model for Ringerike waterworks, Norway

Abstract Groundwater abstraction wells located in aquifers hydraulically connected with rivers or lakes will induce bank filtration if the water level aquifer is lowered below surface-water level. Many groundwater works utilize this induced infiltration to increase capacity of their wells. Unfortunately, organic-rich surface may alter aquifer’s redox geochemistry, and mobilize iron and/or manganese. Ringerike southeastern Norway operates filtration. Manganese concentrations abstracted began 19 years after start operations, stabilized at an elevated 8 later. The estimated manganese retardation ( R sorp = 45±18) from a simplified advection-sorption model comparable observed range 36 < obs 50, assuming residence time t gw ~200 days. based on limited sediment composition hydrochemical data, which introduces significant uncertainty . However, same range, good fit between PHREEQC simulated indicates that sorption possible explanation for delayed breakthrough waterworks’ production Comparable schemes are advised establish observation well(s) well field early detection fronts. This would facilitate (1) longer available remediation measures evaluation, (2) less be desorbed during stage.