Van Beek C.G.E.M.,KWR Watercycle Research Institute |
Dusseldorp J.,Water Utility Oasen |
Joris K.,Water Utility Pidpa |
Huysman K.,Water Utility Pidpa |
And 5 more authors.
Journal of Water Supply: Research and Technology - AQUA | Year: 2016
In groundwater treatment, after aeration, iron(II) is precipitated in rapid sand filtration (RSF) by homogeneous, heterogeneous and biological oxidation. The contribution of homogeneous iron(II) oxidation may be calculated from equations and constants available in the literature. Heterogeneous iron(II) oxidation produces hydrous ferric oxides coated filter sand, resulting in a growing filter bed height, from which the contribution of heterogeneous iron(II) oxidation may be estimated. The complement is contributed by biological iron(II) oxidation. At present this contribution may also be estimated by Gallionella spp. counts by quantitative real-time polymerase chain reaction. Based on field data of drinking water treatment plants from the Netherlands and Belgium, it appears that at pH ≈ 7.5 biological iron(II) oxidation is the main iron(II) removal process. At higher pH homogeneous iron(II) oxidation becomes dominant, while at lower pH heterogeneous iron(II) oxidation delivers a relevant contribution. The distribution of these oxidation processes is influenced by RSF operation such as presence of supernatant water, wet or dry (trickle) filtration, oxygen concentration, filter velocity, etc. Experience shows that the distribution between these three iron(II) oxidation processes may change over time. These results are important for RSF operation, iron sludge production, and fields like chemical well clogging. © IWA Publishing 2016.
van Beek C.G.E.M.,KWR Watercycle Research Institute |
de Zwart A.H.,Technical University of Delft |
Balemans M.,KWR Watercycle Research Institute |
Kooiman J.W.,KWR Watercycle Research Institute |
And 5 more authors.
Water Research | Year: 2010
Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of larger particles. However, the particle concentration in groundwater derived from abstraction wells, with high groundwater flow velocities, is much lower than in groundwater from monitor wells, with minimal flow velocities. This inconsistency points to exhaustion of the particle supply in the aquifer around wells due to groundwater abstraction for many years. The particle size distribution can be described with the help of a power law or Pareto distribution. Comparing the measured particle size distribution with the Pareto distribution shows that particles with a diameter >7 μm are under-represented. As the particle size distribution is dependent on the flow velocity, so is the value of the "Pareto" slope β. © 2009 Elsevier Ltd. All rights reserved.