Innovation
1.1.1 - Least-cost planning in water management
Presently the design of water supply and wastewater systems is standardised to a great extent and is carried out according to commonly accepted rules by all engineers. Important input data are mainly the number of consumers and person equivalents to be treated and the quality requirements of the outflow of the treatment facility. In Germany for instance engineers are calculating that every person will consume 150 litres of water and discharge the same amount of wastewater comprising 60 g of BOD5 daily. These figures, however, can differ very much from site to site. Accurate measurements show a range for water consumption of 60 to 250 l per capita and day, depending on the municipality or institution examined. So a well-done audit of the water flow will be absolutely necessary in order to optimise the layout of a system.
Learning from the least-cost planning approach in the electricity sector, where utilities rather invested in new efficient refrigerators for their clients than to erect an additional power plant, Zer0-M wants to implement this idea in several pilot plants. The least cost planning approach shall allow to identify the most effective solution from a wide array of possibilities. Investments into water-saving appliances in the households (e.g. water saving toilets) decrease water consumption. The sole installation of water meters in an apartment block in Hamburg reduced the water consumption by 15 % due to greater awareness of users. Grey water (non-toilet wastewater) collection and reuse after treatment for low-grade purposes can liberate valuable freshwater resources.
The target is a win-win-strategy where all partners benefit:
consuming less water means lower costs for water supply and water treatment
wastewater treatment complying with quality requirements for reuse means a new water and nutrients resource (e.g. for irrigation)
reduction of wastewater quantity and pollution contributes to the protection of the environment
Cost-effectiveness means in this case also to reduce the external costs. Centralised and decentralised systems may be investigated in order to identify the most efficient scheme. Combinations of both are also possible.
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