RIVERBANK FILTRATION IN THE NETHERLANDS: WELL FIELDS, CLOGGING AND GEOCHEMICAL REACTIONS

摘要

River Bank Filtration (RBF) contributes ca. 7% (80 Mm~3/a) to the national drinking water supply in the Netherlands, through a total of 26 well fields. These RBF well fields are classified on the basis of (1) the main driving mechanism of flow (polder or pump driven); (2) RBF periodicity (flow direction temporarily reversing or not), (3) type of riverbed (sand or gravel), and (4) type of contact of river with aquifer (with or without intercalated aquitard(s)). Three case studies are reviewed which demonstrate the water quality, geochemical reactions and clogging phenomena in differing systems. The mass balance approach, also called 'reverse modeling', is applied to identify and quantify the extent of the most important hydrogeochemical reactions at the three case study sites. Clogging of the river bed seems to be a problem in the Netherlands only in RBF systems with a true gravel bed such as Roosteren along the Meuse River, and on sites where sludge is strongly accumulating due to structurally reduced river flows, as in the Hollandsch Diep estuary which was dammed in 1971 as part of the Delta Works.