Biological iron and manganese removal, pilot and full scale applications
Both manganese and iron are found in surface and ground waters at varying concentration levels. When present even at low concentrations they can be linked to the following problems: discolouration, turbidity and taste problems or form slime and iron noxide or manganese dioxide accumulations in pipes. Both metals promote the growth of certain types of chlorine tolerant micro-organisms in water distribution systems. This biota, as in Walkerton, can provide protected sites for noxious organisms and consequently, vastly increase the costs of cleaning and sterilizing systems that contain organisms dangerous to human health. Although there is little evidence that the consumption of water with natural concentrations of these metals have adverse effects on public health, and they are in fact essential elements for human diet, they do remain problematic from an aesthetic, technical and economic point of view. The Guidelines for Canadian Drinking Water has a recommended limit for aesthetic reasons for iron of 0.3 mg/l and an objective concentration target of 0.05 mg/l. The recommended limit for aesthetic reasons for manganese is 0.05 mg/l and the objective concentration is 0.01 mg/l.. Ontario drinking water objectives have aesthetic objectives of 0.05 mg/l or manganese and 0.30 mg/l for iron.