The water availability in an area like the Iberian Peninsula is limited. Problems such as the ecologic flows maintenance, aquifer salinization or Riparian forest disappearance are just some examples of the effects derived from the hydraulic resources overexploitation. Therefore, the development of policies and attitudes to achieve a rational consumption of this scarce good are fundamental. When talking about water in buildings, it is necessary to raise the reduction of its consumption and development of alternatives such as the use of rain or grey water.
Water saving is of crucial importance for the entire population and especially for the construction technicians in order to reduce the environmental impacts derived from water scarcity. In the following sections, different water saving systems for buildings and landscaped areas that minimise the water waste up to a 40% and reduce its economic cost are presented.
There are new taps where the design facilitates the saving of water thanks to its easy drive in front of the old double-command taps. However, in case of not replacing old taps, different accessories can be installed to reduce the flow of water or to aerate it.
Single-lever taps are widely used in the domestic sector because their simple use and aesthetic. They are taps which the opening, closing and mixing of water is driven by the same lever. The water flow is regulated by moving the lever up and down and the temperature changes by turning the lever from right to left.
Reducing the water flow without affecting comfort is one of the most used strategies to reduce the consumption. Regulators or flow limiters do this function as well as the ecodisks, also known as efficient disks, that limit the lever with the aim of reducing the maximum water flow.
Thermostatic taps are adapted to shower taps and bath-shower taps and have a temperature selector. They are made of thermal sensible materials that contract and expand depending on the temperature. The energy consumption reduction is compressed between 7-17%, in addition to the water saving.
Timed taps are widely used in public spaces and in the service sector. They are activated by pressing a button. Water runs during a certain period of time and stops automatically. The reduction of the consumption is expected to be between the 30 and 40%. There are taps that can be activated with the feet and arms, suitable for geriatric and health care facilities. Nevertheless, the maximum water and energy saving is achieved by using electronic taps, also known as taps with infrared detection. There are models that make possible to mix cold and hot water. The opening of the tap is activated by placing the hands under the water exit and closes automatically when the hands are removed.
There are other economic solutions to reduce water consumption in taps. The installation of accessories such as aerators, flow regulators and reducers are a good idea. The usual consumption in traditional taps is 15 l/min. If reducing mechanisms or aerators are installed, consumption can be reduced to about 4-8 l/min.
Finally, individual counters for hot and cold water are key elements to control the wastewater through a periodical reading of them, promoting a policy of saving among users.
The water use in household appliances accounts for the 20% of the total energy and water consumption in the domestic sector. Then, the purchase of class A + or higher appliances will lead to an energy and water saving.
The washing machines can be considered efficient when they consume less than 7 litres per wash. These washing machines can incorporate the following mechanisms, among others:
Likewise, it is recommended to use biodegradable detergents and ceramic pearls that can save up to the 85% of the detergent consumed. These ceramic pearls are made up of different minerals that reduce the water hardness and generate a surfactant action in the washing.
Efficient dishwashers are those that use less than 1.85 liters of water per person (12 litres of water per washing cycle). When buying a dishwasher, one that incorporates the following water and energy saving systems is preferred:
The most common used toilets, especially in the domestic sector, are the gravity ones. This system uses the strength of the water discharge to clean the toilet. There are different systems to adjust or limit the volume of the discharge in toilets with a deposit attached to the toilet bowl. The disruption of the discharge to avoid the total emptying of the tank is carried out by means of a pushbutton or a handle that for the exit of water. The installation of a double push button is based on the same principle. The push button is usually divided into two different parts in size so that the user can easily recognize them. Each one corresponds to a specific volume of water, 3 or 6 litres generally. In toilets with an elevated tank, only a counterweight can be placed to interrupts the flow when the handle is not activated.
Another type of toilets are the pressurised discharge ones. These systems are usually found in public buildings. They are operated by an automatic closing tap (mechanical or electronic) installed on a derivation of the internal water network. The discharge pressure comes directly from the network, so the cleaning is much more effective. When there is no water tank attached to the toilet, there is more space and the high pressure of the network avoids the conducts obstruction. In the market, it already exists two-pulse fluxmeters for 3 and 6 liters. However, they require duplicating the installation of water. Electronic fluxes are based on the same system as timed fluxes but are activated through an electronic system based on presence detection. The disruption interrupt system is usually timed.
The urinals have a maximum discharge of 6 liters, but nowadays all the new urinals that are installed have a much lower consumption. As in the toilets, the discharge is usually pressurized by timed or electronic fluxes. Because they require little water pressure, the fluxors can be installed in any type of building.
Dry toilets are based on the separation of solids and liquids and are suitable for warm and dry climates. They are implemented in single-family homes that are isolated in areas where there is no sanitary water network. The liquid part runs through the base plate of perforated concrete and is filtered on the ground. In the solid part, garbage from the garden or organic waste can be added and this will also facilitate the absorption of liquids. The installation of a wind extractor or an electric fan is recommended to extract the bad odours from the organic decomposition.
In isolated single-family homes or buildings destined for other uses that have a garden area as well as in green public spaces, it is important to economize the use of water. There are several saving and maintenance reduction strategies that can be adopted, including choosing a suitable irrigation system for the type of planted vegetation, an adequate irrigation program, a rainwater recovery system or a soil protection mechanism to avoid condensation.
The sprinkler irrigation system is made up of mobile devices that are fixed to a secondary water distribution network. It obtains water from a well or underground tank and distributes it by gravity or by pumping. The water consumption is less than the required in the irrigation by grooves or flood since it is adjustable. However, if compared to the drip irrigation system or micro-irrigation, it presents several disadvantages: the consumption is higher and the calculation of distances between sprinklers must be uniform in the 80%. This last system provides water constantly and in small amounts to the roots of the plants, maintaining a stable level of humidity. As it is groundwater, the water losses by evaporation are avoided, optimizing the water use. The system consists of small diameter pipes with valves next to each irrigation point, to which an emitter is connected. Dryers or emitters can be regulated electronically.
There are other factors that play an important role in water optimization and that are progressively being applied to the project, realization and maintenance of green zones at a private and public level. Xeriscaping is based on the use of vegetable species with low water necessity and the adaptation of the garden to the climatic conditions of the area. A previous analysis of the soil to determine the physical, chemical and topographical characteristics of the garden, as well as an exhaustive study of the climate or microclimate of the area is needed. Based on these two studies, the design, vegetation and optimum irrigation system for the garden will be determined. Among others, it takes into account the protection or coating of mulch through plant resources to avoid the evaporation of water that contributes to the erosion and surface spillage of the soil as well as the constant maintenance of the garden. In some municipalities of Spain, urban planning managers are promoting this type of gardening, implanting it in public gardens, with the aim of promoting the maximum water saving and serve as an example to the population. Some town councils have already published ordinances regulating irrigation water sources, promoting the recovered, underground and rainwater, and obligating the construction of a dual distribution network to take advantage of the second water quality.
Water pollution has increased in the recent years as a result of poor urban, industrial and agricultural wastewater management. Currently, there are advanced processes in which the treated effluents present a high quality and where it is possible to start thinking about reuse. Nevertheless, for developing countries, other techniques have to be applied from the point of view of the economic cost. There are methods in whereby the only requirement is to have a terrain. They consist in the purification of water through ponds with aquatic plants. As the concentration of plants increases, so does the concentration of dissolved oxygen that bacteria can use to degrade organic matter. This treatment not only eliminates organic matter and sediments present in residual water, but also eliminates nutrients, dissolved salts, heavy metals and pathogenic organisms.
In these facilities, both wastewater and industrial wastes are collected and treated, either jointly or separately, depending on the municipalities. Urban water is the one generated by different human activities and can be classified depending on its origin in: black water, grey water (they come from bath water, sink ...) and white or rainwater.
The idea of using the soil for purifying wastewater from cities dates back to classical antiquity. For small populations, it is a system that fits perfectly with their requirements, since it can guarantee a sufficient purification and the costs of installation and maintenance are affordable.
When talking about a natural purification system, it refers to the procedures or techniques in which the elimination of polluting substances of the urban wastewater is produced by using components of the natural environment without adding any chemical. Habitually two groups of natural purification techniques are differentiated: treatment methods that consist in the application of water on the ground and aquatic systems.
The natural soil has sufficiently wide ecological limits to purify the wastewater generated by a dispersed or concentrated population in small towns, as long as the discharges are biodegradable and the equivalent inhabitant ratio/filter surface is appropriate. This means that they would not be suitable for treating wastewater from industries. It is also necessary to take into account the protection of the receiving environment, which in these cases are usually aquifers.
Water is an important factor in the sustainable development of societies. It is our responsibility to make a good use of this natural resource. Saving, reusing and taking advantage of water are three basic concepts more and more present in our lives since the goal is to extend the water cycle.
The characteristics of rainwater make it perfectly usable for domestic and industrial uses. The existing rainwater collection facilities basically consist of channelling the rainwater accumulated on the collectors of buildings. The study of the precipitation of each municipality, will allow designing the rainwater tank that guarantees a reserve of water intended to be used for several purposes such as watering the garden. Thus, if reusing rainwater, it is possible to save, in an averaging family, 50000l of drinking water per year. The installation of an adequate water collector must be simple and must require the minimal maintenance. In addition, factors that can disturb the quality of the stored water have to be avoided, such as:
The precondition for a facility to have a well performance is a good planning and a careful selection of the different construction elements. An important point that both the owners and the construction technicians have to take into account are deciding where to collect the rainwater:
Grey water comes from kitchens, bathrooms, toilets, sinks... This water at first sight may have no value, but it can be reusable, protecting the underground water reserves, reducing the load of wastewater and achieving a significant decrease in the cost of drinking water.
By reusing the grey water for tanks, it is possible to save about 50 litres per person per day. Considering an average family of 4 people, this would mean a saving of about 200l/day, which is approximately about the 25% of the daily home consumption. If this system is implanted in hotels, campsites or sports facilities, these figures would be even more important, achieving a drinking water saving of around 30%.
Systems for the reuse of grey waters are highly demanded in single-family homes, neighbourhood communities, hotels, universities and sports facilities such as football fields or swimming pools. These installations consist of separate pipes where the grey waters circulate until reaching deposits, where the water treatment is carried out. Thanks to the purification, the water can be reused for flushing toilets, watering gardens or cleaning outdoors. The grey water reuse equipment is installed in the basements or attics of buildings, with the corresponding drums that collect and treat the water. The necessary pipes to collect the water from the shower and the washbasin are also installed, and some of them will transport the water to be treated and the others will carry the treated water to the toilet tanks to be used and to a water hydrant, if necessary.
Nowadays, the quality of surface water in Spain is not satisfactory. The state of the majority of the rivers located in the northern half part of the peninsula have an optimal degree of conservation, but the contamination of the water grows as they pass through urban and industrial areas, reaching a very degraded state in their medium and final rivers sections. This gets worse when it comes to the southern half of the peninsula: the water quality in the headwaters of rivers is worse since there is less flow rate and hence, the concentration of pollutants is higher.
The treatment of water from rivers is more complex due to the water has been exposed to materials and microorganisms. Depending on the time of the year, the levels of turbidity, mineral content and degree of pollution vary (in summer the flow rate of rivers is less abundant and then, more cloudy than in winter).
Water from deep underground sources, filtering galleries or natural springs present a good quality after analysing them through chemical analysis, and can be directly used for consumption. These waters are generally naturally potable. A treatment with chlorine is recommended to protect the water from possible disturbances in the distribution network that can lead to a contamination. If the water is not potable in a natural way, it will require to be treated in the same way with a corrective treatment, as it happens with surface water. This corrective or purifying treatment can be physical, chemical or bacteriological and is usually carried out in water purification stations.
The purpose of this corrective treatment is to eliminate the turbidity and colour of water, which means the elimination of suspended, finely divided, not settled particles, which are often accompanied by colloidal or dissolved organic matter, that are not retained by simple filtration. For this, a previous treatment with chemical coagulants is necessary, followed by decanting or clarification and then filtration processes, through a layer of sand. There are two kinds of sand filters: those of slow action and those of fast action, and these are divided into filters of free surface and filters of pressure. In slow filters the water passes through gravity at low speed and the separation of solid materials is carried out by passing the water through the pores of the filtering layer and particles stick to the sand grains. In the fast filters with free surface, water descends by gravity through the sand at a higher speed. It is essential the coagulant treatment to remove as much particles in suspension as possible. The filter is washed with a flow of water in the opposite direction of the filtrate, allowing the drainage of accumulated solids or any other inert materials. Finally, a disinfection treatment is carried out, more or less intense depending on the degree of contamination. To eliminate or reduce the intensity of water tastes or odours, different procedures, depending on the nature of the problem, are recommended, such as: aeration, active coal, use of chlorine or other oxidants, such as ozone, etc., and sometimes combining the prior treatment of natural water with algaecide.
The chemical corrective treatment refers to the correction of the water’s pH, the reduction of its hardness, the elimination of the harmful elements or the addition of certain chemical products, always seeking to improve the water quality. The pH correction can be done by adding lime or sodium carbonate, before or after the filtration process. The reduction of hardness can be done by using simple methods (lime, soda, zeolite or resins) or composite methods (lime-soda, lime-zeolite, lime-resins). The elimination of harmful elements refers to the reduction of the excessive content of iron, manganese, fluoride, arsenic or vanadium. Finally, when talking about the aggregation of chemicals, it refers to the fluoride aggregation.
The bacteriological treatment refers almost exclusively to the chlorine disinfection, by using pure chlorine, chlorogenes salts or hypochlorite. The doses used are generally fixed on the basis of the residual chlorine, whose value must be between 0.05 mg/l and 0.1 mg/l to avoid secondary contamination. For the provision of drinking water, chlorine gas is used, while for medium or small supplies hypochlorites are used. The simplest and cheapest sterilization process is chlorination. However, it has a critical point when the dose of chlorine is exceeded, being harmful for the health and cause of diseases.