Geosmin and 2 methylisoborneol (MIB) are earthy/musty odour compounds produced as secondary metabolites by some cyanobacteria and actinomycetes. At levels as low as 5–10 ng l−1 in drinking water they can result in consumer complaints, and consequently their removal from potable water is a priority for many suppliers. In water treatment plants where taste and odour episodes are common, the homogenous surface diffusion model (HSDM) can be used to estimate powdered activated carbon dose requirements under a range of conditions including inlet concentration and plant flow rates (controlling PAC contact time). Water quality, in particular dissolved organic carbon concentration and character, can affect the required doses of PAC, as can the addition of chemicals such as alum and chlorine. There is significant scope for the more cost-effective utilisation of powdered activated carbon for the mitigation of taste and odours, as well as a wider range of other micro-contaminants, using tools such as the HSDM, in conjunction with knowledge of the effects of water quality and water treatment processes.

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