Intensive urbanisation enhances warming of cities’ ambient and subsoil environment. The local drinking water distribution system (DWDS) is likewise affected. Hotspots of anthropogenic heating were perceived to influence drinking water temperature and pose a threat for microbial drinking water quality. Information on temporal and spatial relation between drinking water temperature and microbial indicating parameters was however scarce. This is especially the case for a full scale unchlorinated DWDS in a metropolitan area. Therefore, this research aimed to explore the spatial and temporal relation between drinking water temperature and microbial indicating parameters Aeromonas and Heterotrophic Plate count (HPC). 11 Years of sample data from the DWDS in the metropole of Amsterdam was explored, with the objective to possibly draw conclusions beyond this DWDS. This DWDS consists of two interconnected subsystems. Each subsystem is fed by its own treatment facility. Areas with repetitive exceedance of threshold temperature (14 oC) for accelerating Aeromonas growth, were not inextricably tied to repetitive exceedance of the Aeromonas standard for safe drinking water. Areas with repetitive exceedance of the Aeromonas standard were often linked to prolonged residence time. For regions on the outskirt of observed DWDS it was suggested that the influence of residence time was more important than the absolute water temperature to explain Aeromonas concentrations.

The transition towards sustainable and resource efficient urban water systems is a major challenge nowadays. To meet the high demands of urban life resources need to be efficiently used and resource recovery from generated “waste” streams should become a “new normal”. Water and wastewater can provide an alternative and environmentally viable source of resources supporting the resilience of natural systems under water stress. There are many resources that can be recovered via the water path, such as water itself, energy and components such as nutrients and metals. However, the urban water system is an assembly of complex and interconnected processes which have to be taken into account in order to create an overall sustainable value. Managing the entire water-energy-nutrient nexus for the built environment requires a full system analysis of the life cycle energy consumption, water consumption, global warming potential and freshwater eutrophication potential of the municipal water and sanitation services. This work is an assessment of the environmental impacts of various urban water systems which aim to the water conservation and resource recovery. Each alternative system was assessed under four main planning scenarios applied at a dwelling level$\colon$ greywater treatment and reuse, rainwater harvesting and use, usage of water-efficient appliances, food waste valorisation via the sewer system. The scenarios were investigated from two different perspectives (eight scenarios in total), all based on the principles of water fit-for-purpose and resource recovery. In the first perspective the four scenarios limited the interventions at a dwelling level, while in the second one additional techniques for phosphorus and nitrogen recovery were applied at a centralised wastewater and sludge management level. The comparative results revealed that the usage of water efficient devices (low-flush toilets, water efficient shower heads, waterless washing machines, waterless dishwashers) at a household level, coupled with centralised wastewater treatment with simultaneous recovery of struvite and biogas, and sludge waste drying to produce biofuels promotes a robust and resource efficient urban water system. This strategy was estimated to offset 79% of the overall embodied energy consumption, 72% of life cycle carbon footprint, 22% of life cycle freshwater eutrophication potential and 56% of embodied water consumption. A sensitivity analysis revealed that the energy requirements for water heating in showers, dishwashers and washing machines and the carbon intensity of the national electricity mix were the most important parameters for determining the comparative life cycle global warming potential results.

The temperature of drinking water is an important parameter, affecting physical, chemical, biological and aesthetic properties of the water. Currently, measurements exceeding the legal limit of 25ᵒC at the tap are exceptional. However, there are reasons to believe that the number of exceedances will increase due to climate change and urbanization. So far the effects of sunlight hours and soil coverage on drinking water temperature have already been quantified quite well. Still lacking is the exact effect of anthropogenic heat sources on these temperatures. In this study more insight is given in the extent of this effect for Rotterdam, and measures are discussed to mitigate or to prevent drinking water warming. First, potential anthropogenic heat sources are identified. By analyzing data on tap temperatures and old soil temperature measurements, several anthropogenic heat sources emerged. A map of the statistically warm drinking water temperatures in Rotterdam, appears to have a lot of resemblance to the city heating system whereabouts. Furthermore, smaller indications point at high voltage power cables and metro lines to be important anthropogenic heat sources. Soil temperature measurements around these potential heat sources confirm some of the expectations. Around high voltage power cables, a limited elevated temperature of 0.6ᵒC is found. Much more alarming results were encountered around the city heating mains. In autumn, primary heating mains warm-up the soil by 4.9 – 5.3ᵒC and secondary heating mains do so by 2.9ᵒC. A temperature elevation of 1ᵒC is measured to a distance of 3.8 - 5.25m and 2.3m, respectively. However, these results are highly dependent of several parameters, like the temperature differences between the air and soil, the thermal properties of the soil, and the depth and state of the anthropogenic heat sources themselves. Several strategies to mitigate the warming of drinking water in the distribution system are applicable. In a general sense, it is most sensible to create a distance between any heat source and the distribution system. By placing drinking water mains in the shade, below grass and away from anthropogenic heat sources, warming of the drinking water can be prevented in a relatively inexpensive manner. Measures targeted at temporary local hotspots can be focused on restraining the heat flux from the heat source to the soil, the heat flux through the soil, and the heat flux from the soil to the drinking water.