Abstract
This chapter analyses the urban water cycle in the smarts cities, describes the current situation, which constitutes a valid but outdated knowledge, adopting the perspective of improving and extending the measures that lead to greater efficiency of the water collection, treatment, supply, sewage, purification, and reuse systems at all stages of the water cycle: the sites, construction, operation, and maintenance of the networks and systems that enable the cycle to be completed effectively. The process of converting a city into smart city includes resources, processes, and services, and all stages of the water cycle are a set of processes, with water as a fundamental resource, which condition the different services to citizens, and therefore, it is necessary to try to establish efficiency improvements in all of them.
TopBackground
Bearing in mind that the integral water cycle is closed, as shown in Figure 1, it is advisable to clarify the different stages through which the resource passes, from the moment of its capture until its return to nature, once it has gone through multiple physical and chemical processes in which, in addition to having consumed significant amounts of energy, some hydraulic inefficiencies have occurred that for a long time were considered inevitable.
Key Terms in this Chapter
Pumping Stations: Facilities that are constructed and equipped to transport water or wastewater from the suction or arrival level to the treatment units, to the upper or outlet level.
Storm Tanks: Storm tanks are elements of the drainage network designed to regulate the flow produced during periods of rain and/or to prevent uncontrolled discharges into the receiving environment (river, sea, etc.).
Coagulation: Process that consists in adding a chemical product (the coagulant) that causes the destabilization of the dispersed colloidal matter and its agglomeration in flocs.
Decanting: Physical process of separating liquids or solids, using the difference in density between the substances that make up a heterogeneous mixture of the wastewater.
Garden Coefficient (Kj): Is the relationship between the evapotranspiration of the reference crop and the evapotranspiration of the garden ET c =ET O · K j .
Evapotranspiration: It is the sum of two phenomena that take place in the crop-soil relationship, the transpiration of the crop and the evaporation of the soil, which constitutes the fundamental loss of water, from which the water requirement of the crops is calculated.
Microclimatic Coefficient (Km): This is the coefficient that takes into account environmental differences. When the external conditions increase the evaporation of the irrigation zone, there are high microclimatic conditions and K m =1 – 1,4, when the microclimatic conditions are medium, K m =1 and; finally, when the microclimatic conditions are low, K m =0,5 – 1.
Flocculation: Chemical process by means of which, with the addition of substances called flocculants, the colloidal substances present in the water are agglutinated, thus facilitating their decantation and subsequent filtering.
Neutralization: A chemical process that consists of adding acids or bases to the waste stream in order to stabilize the pH at a desired value.
Planting Density (Kd): It is the number of crop species per hectare and depends on the separation of the crop lines and the distance between crops in the same line.
Crop Coefficient (Kc): Adjustment coefficient that allows the calculation of actual evapotranspiration from potential evapotranspiration or the evapotranspiration of the reference crop.These coefficients depend fundamentally on the characteristics of each crop, so they are specific to each crop and depend on its state of development and its phenological stages, so they are variable over time. They also depend on the characteristics of the soil and its humidity, as well as on agricultural practices and irrigation.