Designing water supply and wastewater disposal systems in conditions of fuzzy values of prospective water consumption and population base

Summary

Designing municipal water supply and wastewater disposal systems is associated with overcoming various uncertainties of an economic, technical, natural and anthropogenic nature. The most significant of these are the design loads in terms of water consumption and wastewater disposal, as well as the population base that will use these utilities in future years. For this reason, CP 31.13330.2021 recommends not specific values, however, a range of values for specific water consumption, for example, 165–180 l/(day·person). Which one shall be taken into account is the problem. At the same time, designers must understand that the risks that arise in case of overestimation or underestimation of design loads are very high, since in both cases reconstruction will be required involving huge financial investments. A new approach is proposed to substantiate the parameters of water supply and wastewater disposal systems based on a fuzzy representation of the prospective population base and specific water consumption. This approach is based on the study of the area of uncertainty by dividing it into intervals with weighted membership functions, as well as on the application of decision theory methods based on the financial risk matrix. Herewith, the risks are estimated through the life cycle cost under various project implementation scenarios. The developed approach is recommended to be used while substantiating the parameters of prospective water supply and wastewater disposal schemes.

Key words

water and wastewater systems , specific water consumption , population base , choosing the preferred option for the construction and reconstruction of systems