This paper presents a first attempt at an integrated systems analysis of drinking water systems using Microbiological Risk Assessment (MRA) and Material Flow Analysis (MFA) with focus on the comparison of central physical-chemical treatment (conventional system) and local membrane filtration. The MFA shows that energy use is the most significant environmental impact of the three studied drinking water systems, but there are no considerable differences in energy use comparing central physical-chemical treatment and local membrane filtration. According to the MRA, the conventional system might not reduce the microbial risks sufficiently, but such a reduction can not confidently be achieved in a one-step ultrafiltration system either, since membrane filter integrity can hardly be guaranteed over the service life of the equipment. A quite costly two-step membrane filtration system, where water for all household purposes passes microfiltration and further reverse osmosis for drinking and cooking, seems to fulfil this criterion. On the other hand, this system does not reduce the microbial risks from ingestion of water from showers compared with the one-step ultrafiltration alternative. In order to achieve drinking water systems with sufficient microbial barriers and with reasonable costs for operation, a promising solution seems to be a combination of one-step membrane filtration and other methods e.g. biological treatment.

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