Physico-chemical and biological iron removal from potable water

Abstract

A pilot-scale trickling filter was constructed and tested for iron removal from potable water. Iron removal was found to be caused by both biological and physico-chemical iron oxidation. The extent of each oxidation type was assessed. The system was inoculated with mixed culture and its performance was tested under continuous operation at 14 °C. Feed iron concentrations and volumetric flow rates (VFR), ranged between 1–4 mg/l and 1000–3000 ml/min (225–680 m 3/m 2day), respectively. First order kinetics was used to describe the physico-chemical iron oxidation while Monod-type kinetics was used to describe the net biological iron oxidation. An increase of VFR from 1000 to 3000 ml/min reduced the filter's physico-chemical removal efficiency from 93 to 80%, while it remained constant for all the iron feed concentrations (1–4 mg/l) that were tested at each VFR. Bio-oxidation improved filter efficiency by about 5–6%. In all cases there was very good agreement between model predictions and experimental data. A series of experiments were also performed in order to investigate the simultaneous ammonia and iron oxidation. It was found that ammonia influence on iron removal becomes substantial only for high iron and ammonia concentrations. The simplicity of the pilot-scale design, the lack of the need for an external mechanical aeration source and the ease for the design and prediction of the system operation offers a very attractive solution for iron removal from potable water.