Muchos de los 4.200 millones de personas que tienen acceso al agua corriente reciben un servicio de mala o muy mala calidad, especialmente en los países en desarrollo, donde vive alrededor del 80% de la población mundial. La calidad del servicio de suministro de agua tiene muchas dimensiones: continuidad; calidad del agua; presión; y el grado de respuesta de los proveedores de servicios a las quejas de los clientes.

Supply continuity

Continuity of water supply is taken for granted in most developed countries, but is a serious problem in many developing countries, where water is sometimes only supplied for a few hours a day or a few days a week. It is estimated that approximately half of the population in developing countries receives water intermittently.

Water quality

The quality of drinking water has a microbiological and physical-chemical dimension. There are thousands of water quality parameters. In public water supply systems, water should, at a minimum, be disinfected – most commonly through the use of chlorination or the use of ultraviolet light – or may need to be treated, especially for surface water.

water pressure

Water pressures vary at different locations in a distribution system. Water pipes below the street can operate at higher pressures, with a pressure reducer located at each point where water enters a building or home. In poorly managed systems, water pressure can be so low that it only results in dripping water or so high that it causes damage to plumbing fixtures and wasted water. Pressure in an urban water system is typically maintained either by a pressurized water tank serving an urban area, pumping the water into a water tower and relying on gravity to maintain a constant pressure in the system or solely by pumps at the water treatment plant and repeater pump stations.

The effective pressure also varies due to pressure loss due to supply resistance, even for the same static pressure. An urban consumer may have 5 meters of 15 mm pipe from the iron pipe, so the flow from the kitchen tap will be quite free, that is, high flow. A rural consumer may have a kilometer of 22 mm rusted and whitewashed iron pipe, so the flow rate of his kitchen tap will be small.

Gravity water has a small pressure (say ¼ bar in the bath) so it needs wide pipes to allow higher flow rates. This is fine for bathrooms and toilets, but is often inappropriate for showers. A booster pump or hydrophore is installed to increase and maintain pressure. For this reason, urban houses are increasingly using mains pressure boilers (combi), which take a long time to fill a bathtub, but adapt to the high backpressure of a shower.

Una gran variedad de instituciones tienen responsabilidades en el suministro de agua. Una distinción básica es entre las instituciones responsables de la política y la regulación, por un lado, y las instituciones encargadas de prestar servicios, por otro.

Policy and control

Water supply policies and regulation are usually defined by one or several ministries, in consultation with the legislative branch. In the United States, the United States Environmental Protection Agency "Environmental Protection Agency (United States)"), whose administrator reports directly to the President, is responsible for water and sanitation policy and standard setting within the executive branch. In other countries, responsibility for sectoral policy is entrusted to a Ministry of the Environment (as in Mexico and Colombia), a Ministry of Health (as in Panama, Honduras and Uruguay), a Ministry of Public Works (as in Ecuador and Haiti), a Ministry of Economy (as in the German states) or a Ministry of Energy (as in Iran). Some countries, such as Jordan, Venezuela (resumed from 2018) and Bolivia, even have a Ministry of Water. Several ministries often share responsibilities for water supply. In the European Union, important political functions have been entrusted to the supranational level. Political and regulatory functions include establishing rate rules and approving rate increases; the establishment, monitoring and application of standards for service quality and environmental protection; benchmarking the performance of service providers; and reforms in the structure of the institutions responsible for the provision of services. The distinction between policy functions and regulatory functions is not always well defined. In some countries, both are entrusted to ministries, but in others regulatory functions are entrusted to bodies other than ministries.

Dozens of countries around the world have established regulatory bodies for infrastructure services, often including water supply and sanitation, to better protect consumers and improve efficiency. Regulatory agencies may be entrusted with a number of responsibilities, notably approving tariff increases and managing the sector's information systems, including benchmarking systems. They are also sometimes mandated to resolve consumer complaints that have not been satisfactorily addressed by service providers. These specialized entities are expected to be more competent and objective in regulating service providers than departments within government ministries. Regulatory agencies are supposed to be autonomous from the executive branch of government, but in many countries they have often failed to exercise a large degree of autonomy. In the United States, utility regulatory agencies have existed for almost a century at the state level, and in Canada at the provincial level. In both countries they cover various infrastructure sectors. For England and Wales, a water regulatory agency (OFWAT) was created as part of the privatization of the water industry in 1989. In many developing countries, water regulatory agencies were created during the 1990s, in parallel with efforts to increase private sector participation, such as some Latin American countries.

Many countries do not have water regulatory bodies. In these countries, service providers are regulated directly by the local government or the national government. This is the case, for example, of the countries of continental Europe, China and India.

Service provision

Water supply service providers, which are often public utilities, differ in their geographical coverage in relation to administrative boundaries, their sectoral coverage, their ownership structure and their governance arrangements.

Many water utilities provide services in a single city, town or municipality. However, in many countries municipalities have partnered in regional or inter-municipal or multi-jurisdictional public services to benefit from economies of scale. In the United States, these may take the form of special purpose districts that may have independent taxing authority.

In some federal countries, there are water service providers that cover most or all cities and towns in an entire state, such as in all states of Brazil and some states of Mexico. In England and Wales, water supply and sewerage is almost entirely carried out by ten regional companies. Some smaller countries, especially developed countries, have established service providers that cover the entire country or at least most of its major cities and towns. These national service providers are especially common in West Africa and Central America, but also exist, for example, in Tunisia, Jordan and Uruguay. In rural areas, where about half of the world's population lives, water services are typically provided not by public utilities, but by community-based organizations that typically cover one or several villages.

Some water utilities only provide water supply services, while sewerage is under the responsibility of a different entity, for example, Tunisia. However, in most cases, water utilities also provide sewer and wastewater treatment services. In some cities or countries, utilities also distribute electricity. In a few cases, these multiple utilities also collect solid waste and provide local telephone services. An example of this integrated utility can be found in the Colombian city of Medellín. Public services providing water, sanitation and electricity can be found in Frankfurt, Germany (Mainova), Casablanca, Morocco and Gabon, West Africa. Multiple utilities provide certain benefits, such as common billing and the option to subsidize water services with revenue from electricity sales, if permitted by law.

An estimated 10 percent of urban water supply is provided by private or mixed public-private companies, usually under concessions, leases or management contracts. Under these agreements, the public entity legally responsible for the provision of services delegates some or all aspects of the provision of services to the private service provider for a period typically ranging from 4 to 30 years. The public entity remains the owner of the assets. These agreements are common in France and Spain. Only a few parts of the world have water supply systems been completely sold to the private sector (privatisation), such as England, Wales and Chile. In recent years, several cities have returned to the public sector in a process called "remunicipalization".[3]​.

Standardization

International standards for water supply system are covered by the International Classification of Standards (ICS) 91.140.60.[6]​.

Costs and financing

The cost of water supply consists largely of fixed costs (capital costs and personnel costs) and only to a small part of variable costs that depend on the amount of water consumed (mainly energy and chemicals). The total cost of water supply in urban areas of developed countries is approximately $1 to $2 per cubic meter, depending on local costs and local water consumption levels. The cost of sanitation (sewerage and wastewater treatment) is another US$1-2 per cubic meter. These costs are somewhat lower in developing countries. Around the world, only a portion of these costs is typically billed to consumers, while the remainder is financed by direct or indirect subsidy from local, regional or national governments.

In addition to subsidies, investments in water supply are financed through internally generated revenues as well as through debt. Debt financing may take the form of loans from commercial banks, loans from international financial institutions such as the World Bank and regional development banks (in the case of developing countries), and "Bond (finance)" bonds (in the case of some developed countries and some upper middle-income countries).

Metering water supply is usually motivated by one or more of four objectives: First, it provides an incentive to conserve water that protects water resources (environmental objective). Second, it can postpone costly system expansion and save energy and chemical costs (economic objective). Third, it allows a utility to better locate distribution losses (technical objective). Fourth, it allows suppliers to charge for water based on usage, which is perceived by many as the fairest way to allocate water supply costs to users. Metering is considered good practice in water supply and is widespread in developed countries, except the United Kingdom. In developing countries, it is estimated that half of all urban water supply systems are empty and the trend is increasing.

Disease outbreaks

The water supply can become contaminated by pathogens that may come from human excrement, for example due to a breakdown or design flaw in the sanitation system, or by chemical contaminants.

A lo largo de la historia, la gente ha ideado sistemas para hacer más conveniente la obtención y el uso del agua. Viviendo en regiones semiáridas, los antiguos persas del primer milenio a. C. utilizaban el sistema de viaje de agua para acceder al agua en las montañas. El imperio romano tenía cañerías interiores, es decir, un sistema de acueductos y tuberías que terminaban en las casas y en pozos y fuentes públicas para que la gente las usara.

Hasta la época de la Ilustración, se hicieron pocos progresos en el suministro de agua y el saneamiento, y las habilidades de ingeniería de los romanos se descuidaron en gran medida en toda Europa. Fue en el siglo cuando el rápido crecimiento de la población impulsó un auge en el establecimiento de redes privadas de suministro de agua en Londres. La Chelsea Waterworks Company fue establecida en 1723 "para abastecer mejor a la Ciudad y los extremos de Westminster y partes adyacentes con agua".[16]​[17]​ Otras obras hidráulicas fueron establecidas en Londres, incluyendo en West Ham "West Ham (Londres)") en 1743, en el Puente Lea antes de 1767, en Lambeth Waterworks Company en 1785, en West Middlesex Waterworks Company en 1806 y en Grand Junction Waterworks Company en 1811.[18]​[19]​.

El tubo S-bend fue inventado por Alexander Cummings en 1775, pero se conoció como U-bend tras la introducción de la trampa en forma de U por Thomas Crapper") en 1880. El primer grifo de agua atornillado fue patentado en 1845 por Guest & Chrimes, una fundición de latón en Rotherham.[20]​.

En el antiguo Perú, el pueblo Nazca "Nazca (cultura)") empleaba un sistema de pozos interconectados y un curso de agua subterráneo conocido como puquios "Puquio (manantial)"). En España y en América Latina, un curso de agua operado por la comunidad, conocido como acueducto, combinado con un simple sistema de filtración de arena, proporcionaba agua potable. Comenzando en la era romana, un dispositivo de rueda de agua conocido como noria suministraba agua a acueductos y otros sistemas de distribución de agua en las principales ciudades de Europa y Oriente Medio. La infraestructura de abastecimiento de agua de Londres se desarrolló a lo largo de muchos siglos, desde los primeros conductos medievales, pasando por las grandes obras de tratamiento del siglo construidas en respuesta a las amenazas del cólera, hasta los modernos embalses a gran escala.

Las torres de agua aparecieron alrededor de finales del siglo ; a medida que aumentaba la altura de los edificios y se disponía de bombas de vapor, eléctricas y diésel. Cuando aparecieron los rascacielos, necesitaban torres de agua en los tejados.

La técnica de purificación del agua potable mediante el uso de gas cloro licuado comprimido fue desarrollada en 1910 por el Mayor del Ejército de los Estados Unidos (más tarde General de Brigada) Carl Rogers Darnall (1867-1941), profesor de química en la Facultad de Medicina del Ejército. Poco después, el Mayor (más tarde Coronel) William J. L. Lyster (1869-1947) del Departamento Médico del Ejército utilizó una solución de hipoclorito de calcio en una bolsa de lino para tratar el agua. Durante muchas décadas, el método de Lyster siguió siendo el estándar para las fuerzas terrestres de Estados Unidos en el campo y en los campamentos, implementado en la forma de la conocida Lyster Bag (también llamada Lister Bag). El trabajo de Darnall se convirtió en la base de los sistemas actuales de purificación de agua municipal.

La desalinización apareció a finales del siglo , y todavía está limitada a unas pocas áreas.

Durante el comienzo del siglo , especialmente en las zonas de centros urbanos y suburbanos, la infraestructura centralizada tradicional no ha sido capaz de suministrar cantidades suficientes de agua para satisfacer la creciente demanda. Entre las diversas opciones que se han gestionado se encuentra el uso extensivo de la tecnología de desalinización, especialmente en las zonas costeras y en países "secos" como Australia. La descentralización de la infraestructura hídrica ha crecido ampliamente como una solución viable, incluyendo la captación de agua de lluvia y la captación de agua pluvial, donde las políticas tienden finalmente a un uso más racional y al abastecimiento de conceptos de incorporación de agua tales como "Apto para el uso". Los emiratos tienen la tasa de consumo de agua per cápita más alta del mundo, con 133 galones.[21]​.

water treatment

The first documented use of sand filters to purify the water supply dates back to 1804, when the owner of a bleaching works in Paisley, Scotland, John Gibb, installed an experimental filter, selling his unwanted surpluses to the public. The first public treated water supply in the world was installed by engineer James Simpson&action=edit&redlink=1 "James Simpson (engineer) (not yet drafted)") for the Chelsea Waterworks Company in London in 1829.[22]​.

The practice of water treatment soon became widespread, and the virtues of the system became apparent after physician John Snow's research during the 1854 Broad Street cholera outbreak demonstrated the role of the water supply in the spread of the cholera epidemic.[23]

Permanent water chlorination began in 1905, when a defective slow sand filter and a contaminated water supply caused a severe typhoid epidemic in Lincoln "Lincoln (Lincolnshire)"), England.[24] Dr. Alexander Cruickshank Houston used water chlorination to stop the epidemic. Its installation fed water treated with a concentrated solution of calcium chloride.[25]​.

The first continuous use of chlorine in the United States for disinfection took place in 1908 at the Boonton Reservoir (on the Rockaway River), which served as a supply for Jersey City, New Jersey, Jersey City, New Jersey.

Muchos de los 4.200 millones de personas que tienen acceso al agua corriente reciben un servicio de mala o muy mala calidad, especialmente en los países en desarrollo, donde vive alrededor del 80% de la población mundial. La calidad del servicio de suministro de agua tiene muchas dimensiones: continuidad; calidad del agua; presión; y el grado de respuesta de los proveedores de servicios a las quejas de los clientes.

Supply continuity

Continuity of water supply is taken for granted in most developed countries, but is a serious problem in many developing countries, where water is sometimes only supplied for a few hours a day or a few days a week. It is estimated that approximately half of the population in developing countries receives water intermittently.

Water quality

The quality of drinking water has a microbiological and physical-chemical dimension. There are thousands of water quality parameters. In public water supply systems, water should, at a minimum, be disinfected – most commonly through the use of chlorination or the use of ultraviolet light – or may need to be treated, especially for surface water.

water pressure

Water pressures vary at different locations in a distribution system. Water pipes below the street can operate at higher pressures, with a pressure reducer located at each point where water enters a building or home. In poorly managed systems, water pressure can be so low that it only results in dripping water or so high that it causes damage to plumbing fixtures and wasted water. Pressure in an urban water system is typically maintained either by a pressurized water tank serving an urban area, pumping the water into a water tower and relying on gravity to maintain a constant pressure in the system or solely by pumps at the water treatment plant and repeater pump stations.

The effective pressure also varies due to pressure loss due to supply resistance, even for the same static pressure. An urban consumer may have 5 meters of 15 mm pipe from the iron pipe, so the flow from the kitchen tap will be quite free, that is, high flow. A rural consumer may have a kilometer of 22 mm rusted and whitewashed iron pipe, so the flow rate of his kitchen tap will be small.

Gravity water has a small pressure (say ¼ bar in the bath) so it needs wide pipes to allow higher flow rates. This is fine for bathrooms and toilets, but is often inappropriate for showers. A booster pump or hydrophore is installed to increase and maintain pressure. For this reason, urban houses are increasingly using mains pressure boilers (combi), which take a long time to fill a bathtub, but adapt to the high backpressure of a shower.

Una gran variedad de instituciones tienen responsabilidades en el suministro de agua. Una distinción básica es entre las instituciones responsables de la política y la regulación, por un lado, y las instituciones encargadas de prestar servicios, por otro.

Policy and control

Water supply policies and regulation are usually defined by one or several ministries, in consultation with the legislative branch. In the United States, the United States Environmental Protection Agency "Environmental Protection Agency (United States)"), whose administrator reports directly to the President, is responsible for water and sanitation policy and standard setting within the executive branch. In other countries, responsibility for sectoral policy is entrusted to a Ministry of the Environment (as in Mexico and Colombia), a Ministry of Health (as in Panama, Honduras and Uruguay), a Ministry of Public Works (as in Ecuador and Haiti), a Ministry of Economy (as in the German states) or a Ministry of Energy (as in Iran). Some countries, such as Jordan, Venezuela (resumed from 2018) and Bolivia, even have a Ministry of Water. Several ministries often share responsibilities for water supply. In the European Union, important political functions have been entrusted to the supranational level. Political and regulatory functions include establishing rate rules and approving rate increases; the establishment, monitoring and application of standards for service quality and environmental protection; benchmarking the performance of service providers; and reforms in the structure of the institutions responsible for the provision of services. The distinction between policy functions and regulatory functions is not always well defined. In some countries, both are entrusted to ministries, but in others regulatory functions are entrusted to bodies other than ministries.

Dozens of countries around the world have established regulatory bodies for infrastructure services, often including water supply and sanitation, to better protect consumers and improve efficiency. Regulatory agencies may be entrusted with a number of responsibilities, notably approving tariff increases and managing the sector's information systems, including benchmarking systems. They are also sometimes mandated to resolve consumer complaints that have not been satisfactorily addressed by service providers. These specialized entities are expected to be more competent and objective in regulating service providers than departments within government ministries. Regulatory agencies are supposed to be autonomous from the executive branch of government, but in many countries they have often failed to exercise a large degree of autonomy. In the United States, utility regulatory agencies have existed for almost a century at the state level, and in Canada at the provincial level. In both countries they cover various infrastructure sectors. For England and Wales, a water regulatory agency (OFWAT) was created as part of the privatization of the water industry in 1989. In many developing countries, water regulatory agencies were created during the 1990s, in parallel with efforts to increase private sector participation, such as some Latin American countries.

Many countries do not have water regulatory bodies. In these countries, service providers are regulated directly by the local government or the national government. This is the case, for example, of the countries of continental Europe, China and India.

Service provision

Water supply service providers, which are often public utilities, differ in their geographical coverage in relation to administrative boundaries, their sectoral coverage, their ownership structure and their governance arrangements.

Many water utilities provide services in a single city, town or municipality. However, in many countries municipalities have partnered in regional or inter-municipal or multi-jurisdictional public services to benefit from economies of scale. In the United States, these may take the form of special purpose districts that may have independent taxing authority.

In some federal countries, there are water service providers that cover most or all cities and towns in an entire state, such as in all states of Brazil and some states of Mexico. In England and Wales, water supply and sewerage is almost entirely carried out by ten regional companies. Some smaller countries, especially developed countries, have established service providers that cover the entire country or at least most of its major cities and towns. These national service providers are especially common in West Africa and Central America, but also exist, for example, in Tunisia, Jordan and Uruguay. In rural areas, where about half of the world's population lives, water services are typically provided not by public utilities, but by community-based organizations that typically cover one or several villages.

Some water utilities only provide water supply services, while sewerage is under the responsibility of a different entity, for example, Tunisia. However, in most cases, water utilities also provide sewer and wastewater treatment services. In some cities or countries, utilities also distribute electricity. In a few cases, these multiple utilities also collect solid waste and provide local telephone services. An example of this integrated utility can be found in the Colombian city of Medellín. Public services providing water, sanitation and electricity can be found in Frankfurt, Germany (Mainova), Casablanca, Morocco and Gabon, West Africa. Multiple utilities provide certain benefits, such as common billing and the option to subsidize water services with revenue from electricity sales, if permitted by law.

An estimated 10 percent of urban water supply is provided by private or mixed public-private companies, usually under concessions, leases or management contracts. Under these agreements, the public entity legally responsible for the provision of services delegates some or all aspects of the provision of services to the private service provider for a period typically ranging from 4 to 30 years. The public entity remains the owner of the assets. These agreements are common in France and Spain. Only a few parts of the world have water supply systems been completely sold to the private sector (privatisation), such as England, Wales and Chile. In recent years, several cities have returned to the public sector in a process called "remunicipalization".[3]​.

Standardization

International standards for water supply system are covered by the International Classification of Standards (ICS) 91.140.60.[6]​.

Costs and financing

The cost of water supply consists largely of fixed costs (capital costs and personnel costs) and only to a small part of variable costs that depend on the amount of water consumed (mainly energy and chemicals). The total cost of water supply in urban areas of developed countries is approximately $1 to $2 per cubic meter, depending on local costs and local water consumption levels. The cost of sanitation (sewerage and wastewater treatment) is another US$1-2 per cubic meter. These costs are somewhat lower in developing countries. Around the world, only a portion of these costs is typically billed to consumers, while the remainder is financed by direct or indirect subsidy from local, regional or national governments.

In addition to subsidies, investments in water supply are financed through internally generated revenues as well as through debt. Debt financing may take the form of loans from commercial banks, loans from international financial institutions such as the World Bank and regional development banks (in the case of developing countries), and "Bond (finance)" bonds (in the case of some developed countries and some upper middle-income countries).

Metering water supply is usually motivated by one or more of four objectives: First, it provides an incentive to conserve water that protects water resources (environmental objective). Second, it can postpone costly system expansion and save energy and chemical costs (economic objective). Third, it allows a utility to better locate distribution losses (technical objective). Fourth, it allows suppliers to charge for water based on usage, which is perceived by many as the fairest way to allocate water supply costs to users. Metering is considered good practice in water supply and is widespread in developed countries, except the United Kingdom. In developing countries, it is estimated that half of all urban water supply systems are empty and the trend is increasing.

Disease outbreaks

The water supply can become contaminated by pathogens that may come from human excrement, for example due to a breakdown or design flaw in the sanitation system, or by chemical contaminants.

A lo largo de la historia, la gente ha ideado sistemas para hacer más conveniente la obtención y el uso del agua. Viviendo en regiones semiáridas, los antiguos persas del primer milenio a. C. utilizaban el sistema de viaje de agua para acceder al agua en las montañas. El imperio romano tenía cañerías interiores, es decir, un sistema de acueductos y tuberías que terminaban en las casas y en pozos y fuentes públicas para que la gente las usara.

Hasta la época de la Ilustración, se hicieron pocos progresos en el suministro de agua y el saneamiento, y las habilidades de ingeniería de los romanos se descuidaron en gran medida en toda Europa. Fue en el siglo cuando el rápido crecimiento de la población impulsó un auge en el establecimiento de redes privadas de suministro de agua en Londres. La Chelsea Waterworks Company fue establecida en 1723 "para abastecer mejor a la Ciudad y los extremos de Westminster y partes adyacentes con agua".[16]​[17]​ Otras obras hidráulicas fueron establecidas en Londres, incluyendo en West Ham "West Ham (Londres)") en 1743, en el Puente Lea antes de 1767, en Lambeth Waterworks Company en 1785, en West Middlesex Waterworks Company en 1806 y en Grand Junction Waterworks Company en 1811.[18]​[19]​.

El tubo S-bend fue inventado por Alexander Cummings en 1775, pero se conoció como U-bend tras la introducción de la trampa en forma de U por Thomas Crapper") en 1880. El primer grifo de agua atornillado fue patentado en 1845 por Guest & Chrimes, una fundición de latón en Rotherham.[20]​.

En el antiguo Perú, el pueblo Nazca "Nazca (cultura)") empleaba un sistema de pozos interconectados y un curso de agua subterráneo conocido como puquios "Puquio (manantial)"). En España y en América Latina, un curso de agua operado por la comunidad, conocido como acueducto, combinado con un simple sistema de filtración de arena, proporcionaba agua potable. Comenzando en la era romana, un dispositivo de rueda de agua conocido como noria suministraba agua a acueductos y otros sistemas de distribución de agua en las principales ciudades de Europa y Oriente Medio. La infraestructura de abastecimiento de agua de Londres se desarrolló a lo largo de muchos siglos, desde los primeros conductos medievales, pasando por las grandes obras de tratamiento del siglo construidas en respuesta a las amenazas del cólera, hasta los modernos embalses a gran escala.

Las torres de agua aparecieron alrededor de finales del siglo ; a medida que aumentaba la altura de los edificios y se disponía de bombas de vapor, eléctricas y diésel. Cuando aparecieron los rascacielos, necesitaban torres de agua en los tejados.

La técnica de purificación del agua potable mediante el uso de gas cloro licuado comprimido fue desarrollada en 1910 por el Mayor del Ejército de los Estados Unidos (más tarde General de Brigada) Carl Rogers Darnall (1867-1941), profesor de química en la Facultad de Medicina del Ejército. Poco después, el Mayor (más tarde Coronel) William J. L. Lyster (1869-1947) del Departamento Médico del Ejército utilizó una solución de hipoclorito de calcio en una bolsa de lino para tratar el agua. Durante muchas décadas, el método de Lyster siguió siendo el estándar para las fuerzas terrestres de Estados Unidos en el campo y en los campamentos, implementado en la forma de la conocida Lyster Bag (también llamada Lister Bag). El trabajo de Darnall se convirtió en la base de los sistemas actuales de purificación de agua municipal.

La desalinización apareció a finales del siglo , y todavía está limitada a unas pocas áreas.

Durante el comienzo del siglo , especialmente en las zonas de centros urbanos y suburbanos, la infraestructura centralizada tradicional no ha sido capaz de suministrar cantidades suficientes de agua para satisfacer la creciente demanda. Entre las diversas opciones que se han gestionado se encuentra el uso extensivo de la tecnología de desalinización, especialmente en las zonas costeras y en países "secos" como Australia. La descentralización de la infraestructura hídrica ha crecido ampliamente como una solución viable, incluyendo la captación de agua de lluvia y la captación de agua pluvial, donde las políticas tienden finalmente a un uso más racional y al abastecimiento de conceptos de incorporación de agua tales como "Apto para el uso". Los emiratos tienen la tasa de consumo de agua per cápita más alta del mundo, con 133 galones.[21]​.

water treatment

The first documented use of sand filters to purify the water supply dates back to 1804, when the owner of a bleaching works in Paisley, Scotland, John Gibb, installed an experimental filter, selling his unwanted surpluses to the public. The first public treated water supply in the world was installed by engineer James Simpson&action=edit&redlink=1 "James Simpson (engineer) (not yet drafted)") for the Chelsea Waterworks Company in London in 1829.[22]​.

The practice of water treatment soon became widespread, and the virtues of the system became apparent after physician John Snow's research during the 1854 Broad Street cholera outbreak demonstrated the role of the water supply in the spread of the cholera epidemic.[23]

Permanent water chlorination began in 1905, when a defective slow sand filter and a contaminated water supply caused a severe typhoid epidemic in Lincoln "Lincoln (Lincolnshire)"), England.[24] Dr. Alexander Cruickshank Houston used water chlorination to stop the epidemic. Its installation fed water treated with a concentrated solution of calcium chloride.[25]​.

The first continuous use of chlorine in the United States for disinfection took place in 1908 at the Boonton Reservoir (on the Rockaway River), which served as a supply for Jersey City, New Jersey, Jersey City, New Jersey.