Iron coatings in pilot dry groundwater biofilters

摘要

In drinking water production from groundwater in the Netherlands, iron and ammoniumare often removed in one dry biofiltration step. Iron removal in these filters is supposedto be a combination of two physical-chemical processes: flocculation-filtration andadsorptive oxidation. Nitrification was studied alone and in combination with iron removalin a pilot-scale dry biofilter setup, where both iron removal processes were imitated byeither direct spraying or pre-oxidation of ferrous iron. Nitrification was evaluated bychemical analyses of the water and molecular techniques and iron removal by chemicalanalyses of the water and the filter coatings. The experiment was performed at two testlocations with distinctly different water qualities. For both iron removal processes,nitrification was hindered by iron. Ammonia-oxidizing bacteria dominated over archaea inall columns. Despite equal operational conditions and loading of iron and ammonium,large differences were observed between both test location in floc formation during preoxidationand in coating formation.