Drinking Water Engineering and Science Discussions www.drink-water-eng-sci-discuss.net 1996-9473 1996-9481 1 1 2008 10.5194/dwesd-1-87-2008 http://www.drink-water-eng-sci-discuss.net/1/87/2008/ http://www.drink-water-eng-sci-discuss.net/1/87/2008/dwesd-1-87-2008.html http://www.drink-water-eng-sci-discuss.net/1/87/2008/dwesd-1-87-2008.pdf 87 115 2008-06-05 Removal of both dissolved and particulate iron from groundwater K. Teunissen k.teunissen@tudelft.nl A. Abrahamse H. Leijssen L. Rietveld H. van Dijk Delft University of Technology, PO Box 5048, 2600 GA Delft, The Netherlands Kiwa Water Research, PO Box 1072, 3430 BB Nieuwegein, The Netherlands Vitens Flevoland, PO Box 1090, 8200 BB Lelystad, The Netherlands Iron is the primary source for discolouration problems in the drinking water distribution system. The removal of iron from groundwater is a common treatment step in the production of drinking water. Even when clear water meets the drinking water standards, the water quality in the distribution system can deteriorate due to settling of iron (hydroxide) particles or post-treatment flocculation of dissolved iron. Therefore it is important to remove dissolved and particulate iron to a large extent. This paper describes the study towards the current iron removal processes and experimental work towards improving removal of dissolved and particulate iron. The study was carried out at groundwater treatment plant Harderbroek, consisting of aeration, rapid sand filtration and tower aeration. The research contains two parts: 1) a particle fingerprint of the treatment, resulting in a quantification of particles breaking through the rapid sand filtration. 2) Small column experiments on the oxidation and filterability of iron. The fingerprint showed that operational events such as switching on/off of filters and backwashing have a significant impact on the volume concentration of particles breaking through the filter. A frequency plot of the different size ranges of particles indicates that mainly the filterability of the middle size ranges (2–7 μm) of particles was influenced by switching a filter on/off. A backwash event mainly affects the bigger particle size ranges. The column experiments showed that in the cascade effluent the majority of the iron is dissolved iron(II), indicating that the oxidation of iron(II) to iron(III) is the rate determining step at Harderbroek, which is limited by pH. Dosing caustic soda resulted in a significant increase of the oxidation rate and improved the removal of iron(II) in the column. Crushed limestone filtration gave promising results, but the contact time applied was too short to completely oxidize iron(II). Hatva, T.: Iron and Maganese in groundwater in Finland: Occurrence in glacifluvial aquifers and removal by biofiltration, National board of water and environment, Helsinki, Finland, 1989. Hult, A.: Filtration of iron during and after oxidation, Effl. Wat. Treat. J. April, 13, 209–215, 1973. Jones, L. and Atkins, P.: Chemistry – Molecules, Matter, and Change. University of Northern Colorado and Oxford University, W. H. Freeman and Company New York 2000. Lerk, C. F.: Enkele aspecten van de ontijzering van grondwater, PhD dissertation, Technical University Delft, The Netherlands, 1965 (in Dutch). Mayer, T. D. and Jarrell, W. M.: Phosphorus sorption during iron(II) oxidation in the presence of dissolved silica, Water Res., 34, 16, 3949–3956, 2000. McNeill, L. S. and Edwards, M.: Iron pipe corrosion in distribution systems, J. Am. Water. Works Ass., 93(7), 88–100, 2001. Mouchet, P.: From conventional to biological removal of iron and manganese in France, J. AWWA, 84(4), 158–167, 1992. O'Conner, J. T.: Iron and Manganese, in: Water Quality & treatment – a handbook of public water supplies, Chapter 11, McGraw Hill, New York, 378–396, 1971. Oomen, J. H. C. M., de Moel, P. J.., and van Dijk, J. C.: Marmerfiltratie van ijzerhoudend grondwater , H2O, 16, 2, 40–44, 1983 (in Dutch). Prince, R. A., Goulter, I., and Ryan, G.: What causes customers complaints about discoloured drinking water? Correlating customer complaints with online monitoing of flow rate and turbidity, Water, 30(2), 62–67, 2003. Robinson Jr., L. R. and Breland, E. D.: removal of iron & manganese from low alkalinity waters, Public Works, 59(2), 72–76, 1968. Salvato, J. A.: Environmental engineering ans Sanitation, 4th Ed., John Wiley and Sons, 1992. Sharma, S. K., Sebwato, C. Petrusevski, B., and Schippers, J. C.: Effect of groundwater quality on adsorptive iron removal, J. Wat. Sup: Resch and Tech. – Aqua. 51.4, 51(4), 199–208, 2002. Sharma, S. K.: Adsorptive iron removal from groundwater, PhD dissertation, Wageningen University/IHE Delft, The Netherlands, 2001. Smith, S. E., Bisset, A., Colbourne, J. S., Holt, D. M., and Lloyd, B. J.: The occurrence and significance of particles and deposits in a drinking water distribution system, Journal of the New England Water Works Association, 111(2), 135–150, 1997. Søgaard, E. G., Medenwaldt, R., and Abraham-Peskir, J. V.: Conditions and rates of biotic and abiotic iron precipitation in selected Danish freshwater plants and microscopic analysis of precipitate morphology, Water Res., 34(10), 2675–2682, 2000. Verberk, J. Q. J. C., Hamilton, L. A., O'Halloran, K. J., Horst, W., and Vreeburg, J. H. G.: Analysis of particle numbers, size and composition in drinking water transportation pipelines: result of online measurements, Water Sci. Technol., 6(4), 35–43, 2006. Vreeburg, J. H. G.: Discolouration in drinking water systems: a particular approach, PhD dissertation, Delft University of Technology, The Netherlands, 2007.