In the production of drinking water from groundwater, iron removal in filters may interfere with nitrification. Microbial nitrification might decline because of irreversible accumulation of iron deposits in pores and on filter material. This paper shows the successful application of two experimental techniques applied at a full-scale water treatment plant in the Netherlands to maintain sustainable nitrification. Filter performances were evaluated by measurements of ammonium in the filter effluent, accumulation of deposits and their removal during backwash, development of the mainly inorganic filter coating and media expansion curves. The application of dual-media drinking water trickling filters, in combination with filter backwash with media expansion, minimizes the irreversible accumulation of iron deposits in the filter. Subsurface aeration results in a lower iron content of the filter coating.

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