Global Water Challenges and Solutions

Global Water Challenges and Solutions

CHAPTER 2 Global Water Challenges and Solutions Satinder Ahuja Ahuja Consulting, Calabash, NC, United States Water nurtures life on this beautiful p...

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CHAPTER 2

Global Water Challenges and Solutions Satinder Ahuja Ahuja Consulting, Calabash, NC, United States

Water nurtures life on this beautiful planet we call Earth. It is composed of 70% water; freshwater comprises only 3% of the total water available to us. Only 0.06% is easily accessible for human use. Over 80 countries in the world suffer from water shortages; this compels almost 1.2 billion people to drink unclean water today. According to the UN, 2.7 billion people will not have clean water by 2025. To make things worse, water-related diseases kill 5 million–10 million people yearly, mostly children, around the world. Contamination of water from various chemicals is a major point of concern because countless inorganic and organic compounds from A to Z (arsenic to zinc) can pollute our groundwater and surface water [1–11]. We have had scores of major water contamination events in recent decades. The most horrendous water pollution problem relates to arsenic contamination of groundwater in Bangladesh. Groundwater pollution by arsenic has affected around 200 million people worldwide, including the United States. In Bangladesh, millions of wells were installed specifically to solve the problem of microbial contamination created a different type of contamination—arsenic. Arsenicosis resulting from drinking arsenic-contaminated water can lead to a protracted painful death. Recent water disasters in the US occurred in Flint, Michigan, and in Wilmington, North Carolina. Instead of buying Lake Huron water from Detroit, the city of Flint began drawing its water from the local river in April 2014. The residents made complaints about burning skin, tremors in their hands, loss of hair, and even seizures. In 2015, a team of scientists from Virginia Tech determined that there were high levels of lead in the water supply of Flint. Unsafe levels have turned up in tap water in many other areas of the country: Washington, DC, in 2001; Columbia, SC in 2005; Durham and Greenville, NC, in 2006; and Jackson, MS, and Sebring, OH, in 2015. In 2009, DuPont* (Chemours) introduced GenX to replace PFOA (perfluorooctanoic acid) in its plant in Fayetteville, NC; this is a compound that is used to manufacture Teflon and coatings for stain-resistant carpeting and waterproof clothes. Since that time, GenX has been detected in the drinking water in Fayetteville, Wilmington, and Brunswick County, NC (2012–17), and in surface waters in Ohio and West Virginia. Levels of GenX in the Advances in Water Purification Techniques. https://doi.org/10.1016/B978-0-12-814790-0.00002-8 Copyright # 2019 Elsevier Inc. All rights reserved.

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drinking water of the Cape Fear Public Utility Authority (CFPUA) in Wilmington averaged 631 ppt (parts per trillion), according to a study by Knappe et al. The EPA drinking water standards for PFOA is 70 ppt. It has been suggested by the North Carolina Department of Environmental Quality that 140 ppt would be an acceptable level for GenX. Unfortunately, CFPUA cannot filter out GenX, and the utility authority is trying to determine the best alternative. Preventing water disasters and attaining water sustainability [1, 2, 8–10] would be an outstanding achievement. To achieve sustainability, we must assure that we meet our needs and avoid compromising the ability of future generations to meet theirs [10]. To attain this objective, we need to address technical, economic, and social issues [8]. Most importantly, we must use water judiciously and reclaim contaminated water. Water reclamation (the act or process of recovering) is absolutely essential because we have managed to pollute our surface water, and even groundwater in some cases, to a point that water needs to be purified for drinking [2]. The discussion below briefly covers water availability, various contamination problems, and some solutions that have been applied globally.

2.1 Global Water Availability Water scarcity is both a natural and a man-made phenomenon. There is enough freshwater on the planet for 7 billion people, but it is distributed unevenly and too much of it is wasted, polluted, and unsustainably managed. Water scarcity affects every continent. Water use has been growing at more than twice the rate of population increase in the last century, and, although there is no global water scarcity as such, an increasing number of regions are chronically short of water. The United States, Canada, and a few other countries have an abundant supply of water; however, a large area of the world suffers from physical water scarcity or lacks economic means to secure water [12]. Around 1.2 billion people, or almost one-fifth of the world’s population, live in areas of physical water scarcity. Another 1.6 billion people, or almost one-quarter of the world’s population, face economic water shortages (where countries do not have the necessary infrastructure to take water from rivers and aquifers). With the existing climate change scenarios, almost half the world’s population will be living in areas of high water stress by 2030 (including 75 million–250 million people in Africa alone). Sub-Saharan Africa has the largest number of water-stressed countries than many other regions in the world. The water scarcity in some arid and semiarid areas could displace as many as 700 million people. Worldwide water consumption is estimated to be around 914,546 billion liters per year (data on water consumption in the world are available from the UN/UNESCO). Agriculture accounts for 70% of all water consumption, industrial usage accounts for 20%, and domestic usage is 10%. In highly industrialized countries, however, manufacturing consumes more than half of the available water. Over the last 50 years, freshwater withdrawals have tripled, and the demand for

Global Water Challenges and Solutions 19 freshwater is increasing by 64 billion cubic meters per year (1 m3 ¼ 1000 L) for the following reasons: ▪ ▪ ▪ ▪

The world’s population is growing by roughly 80 million each year. Changes in lifestyles and eating habits in recent years require more water consumption per capita. Water demand is rapidly increasing because of accelerated energy demand. Energy from biofuels and shale has major impacts on water demand.

The problem of water scarcity is further compounded by the fact that nearly one-third of the population of the world has no toilets—human waste can affect water supplies and cause several diseases from bacteria and parasites. Globally, one-third of all schools lack access to safe water and adequate sanitation. Water shortages in this century are among the main problems faced by many societies. Water, sanitation, and hygiene (WASH) are essential for human health and development. Poor sanitation affects water quality; nearly 80% of diseases in developing countries are associated with water quality. A large majority of countries recognize that both drinking water and sanitation are human rights. Critical gaps in monitoring impede decision-making and progress for the poorest. National financing for WASH is insufficient. Only 17% of the countries apply financial measures to reduce disparities in access to sanitation for the poor, compared to 23% for drinking water. In 2010, a UN resolution declared the human right to “safe and clean drinking water and sanitation.” We need to find ways to dispose of human waste without the use of water. Better yet, we have to find ways to use human waste more effectively.

2.2 Water Quality A review of rural water system sustainability in eight countries in Africa, South Asia, and Central America found an average water project failure rate of 20%–40%. Gina McCarthy, former EPA Chief, delivered a dire warning: The US water supply infrastructure is aging, and states are not prepared to face current and future water challenges, which include scarcity and threats from emerging contaminants [11]. As mentioned in Chapter 1, various sources of contamination are as follows: combustion products of oil (gasoline) and coal, detergents, disinfectants, drugs (pharmaceuticals including endocrine disruptors and illicit drugs), fertilizers, gasoline and its additives, herbicides, insecticides/pesticides, phthalates, radionuclides, and volatile and semivolatile compounds. Volatile organic contaminants (VOCs) and semivolatile contaminants may enter directly into our water resources from various spills, by improper disposal, or from the atmosphere in the form of precipitation. In general, VOCs have high vapor pressures, low-to-medium water solubilities, and low molecular weights. These properties allow them to move freely between

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air and water [6]. Fog plays an important role in cycling neurotoxic mercury species among coastal systems [2]. Fog droplets contain high amounts of monomethylmercury, 3–4 ng/L as compared to 0.1 ng/L typically seen in raindrops. The point- and nonpoint-source pollution occur for a variety of reasons. The impact of water pollution due to a variety of sources, including disinfectants, herbicides, coal ash, fracking, and radionuclides, has been discussed in earlier texts [1d9]. The world’s seas are inundated by a variety of water pollution problems [12]. With a warming planet and acidifying oceans, species from corals to lobsters and fish are succumbing to pathogenic infections. Table 2.1 illustrates the most acute problems in major bodies of water. The widespread use of plastics and their careless disposal has led to the pollution of various bodies of water. Large parts of the Pacific Ocean, often referred to as “plastic oceans,” have formed enormous gyres that are even larger than the size of Texas, and are covered with plastic debris. The Pacific, the largest ocean area on the planet, is over 10 million square miles— approximately the size of Africa—and it is the home to two very large gyres. The Atlantic Ocean holds two more gyres, and there are other plastic oceans in other bodies of water. These microplastics can stunt fish growth and modify their behavior.

2.3 Impact of Climate Disruptions on Water Availability and Quality The impact of climate disruptions on water availability and quality can no longer be ignored. Global surface temperature analysis shows that global trends are higher than those reported by the Intergovernmental Panel on Climate Change [13]. The World Meteorological Organization says that warming effects from greenhouse gases increased by 36% from 1990 to 2014. So far, 160 countries have individually pledged to carry out specific actions to control emissions. The United Nations Environment Programme evaluation shows that this effort will fail to hold a temperature increase of 2°C by 2100. In January 2016, the Department of Housing and Urban Development announced grants totaling $1 billion for 12 states to help communities adapt to climate change by building stronger levees, dams, and drainage systems [14]. One of those grants, $48 million for Isle de Jean Charles, LA, is for moving an entire community struggling with the impacts of climate change. We need to recognize the massive problems the world could face in the coming decades as it confronts a new category of displaced people who are known as climate refugees [15]. Lake Oroville, in California, is at 39% of capacity, and Nevada’s Lake Meade is at 1081.8 ft above sea level as compared to its height of 1200 ft. Mandatory water curbs have been introduced in California. That state and other drought-prone states will have to focus on expanding water infrastructure. It appears that the Western US drought, which began in Texas over 15 years ago, is indicative of a long-term climate pattern. The potential effects of drought will reach far beyond the borders of these states.

Table 2.1 Major bodies of water/areas with serious water pollution problems Suspended Solids

Area

Microbiological

Eutrophication

Chemical

Gulf of Mexico

Severe impact

Caribbean Sea

Aral Sea

Slight impact

Severe impact

Moderate impact Moderate impact Moderate impact Severe impact

Moderate impact Severe impact

Baltic Sea

Moderate impact Slight impact

Moderate impact Moderate impact Severe impact

Yellow Sea

Moderate impact Moderate impact Moderate impact Moderate impact Severe impact

Severe impact

Slight impact

Slight impact

Severe impact

Moderate impact Moderate impact Severe impact

Slight impact

Bohal Sea Congo Basin Benguela Current Lake Victoria Pacific Islands

Moderate impact

Modified from UNEP SEO Report, 2004–2005.

Severe impact Moderate impact Severe impact Slight impact

Moderate impact Moderate impact

Slight impact Severe impact

Moderate impact Moderate impact Severe impact Moderate impact

Solid Wastes

Thermal

Radionuclides

Spills

Moderate impact Moderate impact Slight impact

None known

None known

Slight impact

Slight impact

Slight impact

Severe impact

None known

Slight impact

Slight impact

Slight impact

Moderate impact Slight impact

Slight impact

None known

Slight impact

None known

None known

None known

Severe impact

Slight impact

Severe impact

Moderate impact Severe impact

Slight impact

None known

None known

None known

Severe impact

Slight impact

Severe impact

Slight impact

Moderate impact Moderate impact Moderate impact Severe impact

Moderate impact Severe impact

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Despite the snow in the Sierra Nevada, the water-filled Lake Shasta, the rapids in the Kern River, and the high water level in Lake Mendocino, California is still in a state of drought (see http://www.scwa.ca.gov/files/images/water-supply/reservoir-storage-graph.pdf). Water battles are heating up in Texas, where officials are suing New Mexico and Oklahoma over river water to quench the thirst of its booming population. A water shortage has forced the state to recycle sewage to drinking water. The facility in Big Spring, Texas, has the capacity to produce 2 million gallons of drinking water [16]. Drought in Australia in 2003 forced big cities to develop new water supplies. A desalination plant powered by solar and wind energy now provides half of the drinking water in Perth.

2.4 Monitoring Water Contaminants Water is a clear, colorless liquid, though a layperson might describe water’s color as white or blue. The fact is that many colors that have been ascribed to water relate to the materials that may be present in it. For example, blue water generally refers to ocean water, which gets its color from the reflection of the color of the sky; and we have seas that are described by various other colors because of their appearance: Red Sea, Yellow Sea, Black Sea, and White Sea. Water generated from activities such as laundering, dishwashing, and bathing is described as gray water, and water which has come into contact with fecal matter is called black water. Frequently, municipal water may have an odor at times, and that odor relates to the chlorination of water. A musty odor in drinking water may be the result of by-products of blue-green algae. Our civilization has managed to pollute water sources to the point where we must disinfect water for drinking purposes. To assure water purity, we need to monitor contaminants from arsenic to zinc at ultratrace levels [5, 8, 11]. Some details on ultratrace analyses were provided in Chapter 1. For example, dioxin (2,3,7,8-tetrachloro-dibenzodioxin) at the 200 ppt level can cause abortions in monkeys [17 ]. Polychlorobiphenyls (PCBs) at 0.43 ppb (parts per billion) level can weaken the backbones of trout [18]. This suggests that ultratrace analysis is necessary to monitor materials like PCBs and dioxin [19–21]. We have known for some time now that water that we call potable may actually contain many trace and ultratrace contaminants, as exemplified by an analysis of Ottawa drinking water [22]. It contained insecticides like α-BHC (an isomer of lindane), lindane, and aldrin at ppt levels. In addition, it contained phthalates at significantly higher concentrations. As mentioned in Chapter 1, National Primary Drinking Water Regulations control water quality in the United States, in response to public concern about degraded water quality and the widespread view that pollution of our rivers and lakes is unacceptable. The Clean Water Act (CWA) became law in 1972. Control of point-source contamination traced to specific “end of pipe” points of discharge or outfalls such as factories and combined sewers, was the primary focus of the CWA. Other nations adopted similar measures and have seen improvement in point-source contamination as well. In the United States, potable water must be cleaner than the maximum contaminant level mandated by local, state, and federal guidelines (USEPA national

Global Water Challenges and Solutions 23 primary drinking water regulations). The tests commonly carried out on drinking water are turbidity, total organic carbon, chlorite, chlorine dioxide, fluoride, sulfate, and orthophosphate [13]. Some unregulated substances are also investigated. Surprisingly, testing for arsenic is not performed regularly.

2.5 Water Challenges Worldwide Drinking water comes mainly from the following sources: rivers, lakes, wells, and natural springs. These sources are exposed to a variety of conditions that can cause water contamination. Bottled water is not necessarily safe either. In 2008, Environmental Working Group found arsenic, acetaminophen, caffeine, and nitrates in 10 brands of bottled water. People need to be careful when they drink water in Africa, Asia, and Latin America. The rivers in these areas are frequently considered the most polluted in the world. There are 3 times as many bacteria from human waste as the global average, and 20 times more lead than rivers in developed countries.

2.5.1 Asia In 2004, water from half of the tested sections of China’s seven major rivers was found to be undrinkable because of pollution. The Yangtze, China’s longest river, is “cancerous” with pollution. The pollution from untreated agricultural and industrial wastes could turn the Yangtze into a “dead river” within a short time. This would make it impossible to sustain marine life or provide drinking water to the booming cities along its banks. Almost half of China’s water sources are polluted. Wells and aquifers are contaminated with fertilizers, pesticide residues, and heavy metals such as arsenic and manganese from mining, the petrochemical industry, and domestic and industrial wastes. More than three-fourths (76.8%) of 800 wells monitored in nine provinces and autonomous regions and municipalities, including Beijing, Shanghai, and Guangzhou, failed to meet standards for groundwater in a 2011 national evaluation [23]. Monitoring studies on rivers in India are limited, and the presently reviewed Kaveri River is one such river in southern India that has served as a lifeline (agriculture, drinking water, and industry) for centuries (see Chapter 7 in Ref. [1]). The frequently reported organochlorine pesticides (OCPs) in this river include hexachloro-cyclohexane (HCH), dichloro-diphenyltrichloroethane (DDT), endosulfan, aldrin, dieldrin, and heptachlor epoxide. The levels of some of the OCPs in the Kaveri River exceeded safety guideline values; therefore, these waters are considered a threat to the population because continuous exposure cannot be ruled out. Persistent organic pollutants (POPs), pesticides, organotin compounds, perfluorinated compounds, heavy metals, and other emerging contaminants like pharmaceuticals, personal care products, steroids, hormones, phthalates, plasticizers, etc., have been used in a wide range of agricultural, sanitation, and industrial commodities in the Ganges River Basin, resulting in vigorous deterioration of the river (see Chapter 8 in Ref. [1]). The Ganges is believed to be

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highly polluted with POPs and other contaminants; however, no systematic study and analysis of POPs and other toxins have been conducted. In Japan, the impact of two natural disasters (an earthquake followed by a tsunami) and the consequent human activities significantly impacted the quality of interior and coastal waters (see Chapter 11 in Ref. [1]). Two cases of accidental petrochemical fires in Japan that involved the use of aqueous film-forming foam (AFFF) have been investigated as potential sources of perfluoroalkyl substances (PFASs) in the internal and coastal waters.

2.5.2 Middle East The continuously growing global water scarcity and the evidence for climatic changes require a refocus on reliable and sustainable water supplies, especially in arid and semiarid regions, as they are the most water-deprived regions in the world. Population growth, urbanization, and increasing water demands intensify the pressure on many water resources, causing rapid depletion of supply and quality degradation to a degree that part of the resources may not be safe to use and can cause health and environmental risks. Such adverse development is strongly apparent in the Middle East (for more details see Chapter 10 in Ref. [1]).

2.5.3 Africa Water scarcity, purity, and delivery have become major challenges of humanity, especially in Africa. On this continent, 325 million people lack access to safe water. The majority of those who lack water live in rural areas. Africa is second to Australia in dryness, but it is home to 15% of the global human population and has only 9% of global renewable water resources. Most of Africa’s surface water has become polluted by human activities, and its wells are rapidly becoming dry. Impacts of climate change and climate variability are making water scarcity even more stressful (for more details see Chapter 6 in Ref. [1]).

2.5.4 Europe The quality of water in Europe’s rivers and lakes deteriorated between 2004 and 2005. Almost one-third of Ireland’s rivers are polluted with sewage or fertilizer. The Sarno River in Italy is the most polluted river in all of the Europe, featuring a mix of sewage, untreated agricultural waste, industrial waste, and chemicals. The Rhine, which flows through many European countries, is regarded by many as the dirtiest large river; almost one-fifth of all the chemical production in the world takes place along its banks. Herbicides in drinking water can be deleterious to human health [24]. Three herbicides—amitrole, isoproturon, and trisulfuron were banned in the European Union with effective from September 30, 2016, because of potential groundwater contamination and risks to aquatic life.

Global Water Challenges and Solutions 25

2.5.5 Australia The King River is Australia’s most polluted river, suffering from a severe acidic condition related to mining operations. Land pollution makes up over 80% of all marine and freshwater pollution in Australia. Upwards of 85% of households in Australia contribute to water pollution, whether knowingly or unknowingly, by improperly disposing garbage and waste. The Great Barrier Reef’s water quality has been seriously damaged in recent years.

2.5.6 United States In the United States, nearly 40% of the rivers are too polluted for fishing, swimming, or aquatic life. The Mississippi River drains nearly 40% of the soil and water of continental United States, including its central farm lands. It carries an estimated 1.5 million metric tons of nitrogen pollution into the Gulf of Mexico every year. Nearly 1.2 trillion gallons of untreated sewage, storm water, and industrial waste are discharged into US waters annually, and 46% of the lakes are extremely polluted. Two-thirds of US estuaries and bays are either moderately or severely degraded from eutrophication (nitrogen and phosphorus pollution). Even the most advanced countries, such as the United States, face a water crisis. Most experts agree that the US water policy is in chaos. Decision-making about allocation, repair, infrastructure, and pollution is spread across hundreds of federal, state, and local agencies. About 12,500 tons of antimicrobials and antibiotics are administered to healthy animals on US farms each year. A 2002 US Geological Survey found pharmaceuticals (hormones and other drugs) in 80% of the streams sampled in 30 states. These contaminants are suspected in the increase of fish cancer, deformities, and feminization of the males. Drug companies, by releasing into the environment antibiotic-containing wastewater, are fostering an emergence of deadly resistant bacteria [25]. There can be 50 different drugs in water at one place and time [26]. Zoloft has been detected in water samples and fish tissue in the United States and Canada. Drugs can accumulate as they work their way up the food chain, thus exposing predators to higher levels. Fluoxetin (Prozac), an antidepressant, is excreted unchanged by humans and is environmentally stable. It can cause reduced libido and decreased appetite. Unmetabolized drugs like metformin and others that break down into various metabolites are polluting water; still, the EPA does not regulate a single human drug in drinking water. In 2015, scientists at Virginia Tech detected lead at high levels in the water supply of Flint, Michigan. In an effort to save money, Flint had started using water from the Flint River in April of 2014 instead of Lake Huron water from Detroit. People started complaining about burning skin, hand tremors, hair loss, and even seizures. For almost 19 months, the problem was ignored as the Flint River water corroded the city’s decades-old pipes and leached lead

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into Flint’s water supply. Lead is particularly harmful to kids, as it impacts their rapidly growing brains. The crisis exposed as many as 8000 youngsters under the age of 6 to unsafe levels of lead. This may be the most serious contamination threat facing the country’s water supplies, but it is hardly the only one. In Sebring, Ohio, routine laboratory tests in August 2015 found unsafe levels of lead in the town’s drinking water after workers stopped adding a chemical to keep lead water pipes from corroding. Five months passed before the city told pregnant women and children not to drink the water, and before it shut down taps and fountains in schools [27]. Unsafe levels of lead have been found in tap water in various cities since 2001: in Washington, DC, in 2001, Columbia, SC, in both Durham and Greenville, NC; in Jackson, MS, as well as in scores of other places in recent years. Nearly 3.6 million people in the United States were served by their local or regional drinking water systems’ exceeding the federal lead standard at least once between January 1, 2013, and September of 2015 [28]. Contamination of drinking water supplies by industrial chemicals has been examined by three states: Vermont, New Hampshire, and New York (WSJ, April 26, 2016). For decades, factories have used perfluorooctanoic acid as a plastic coating and to make consumer products such as Teflon nonstick pans, waterproof jackets, and pizza boxes. The problem was first discovered in 2014 near the border of NY and Vermont. The EPA has set 70 ppt as the maximum allowable quantity; the water utility companies must inform the population when the values exceed this limit individually or combined [29]. Contamination of drinking water from perfluorochemicals has been reported from industrial sites where they were produced, and also near military bases and airports [30]. Domoic acid (DA) was detected at high levels in Dungeness crabs and rock crabs by the California Department of Fish and Wildlife [15]. The DA is produced by the marine alga pseudo-nitzschia, which is eaten by shellfish and some small fish. It can cause nausea, diarrhea, and dizziness in humans; and at high concentrations, it can cause seizures, coma, and death.

2.5.7 Latin America Almost 2.1 million of urban and 13.2 million of rural inhabitants in Central America have no access to safe drinking water (see Chapter 4 in Ref. [1]). In addition, 1.1 million urban and 8.7 million rural inhabitants lack access to proper sanitation systems. The access to drinking water and sanitation in Central America is presented in Table 2.2. South America is relatively well endowed with freshwater, although millions of people suffer from restrictions on potable water and proper sanitation systems because of longer drought periods, as well as the lack of an adequate infrastructure and proper governance. It is estimated that 60%d80% of available water is used in agricultural irrigation in South America.

Global Water Challenges and Solutions 27 Table 2.2 Access to drinking water and sanitation Population (%)

Drinking Water (%)

Sanitation (%)

Country

Urban

Rural

Urban

Rural

Urban

Rural

Belize Guatemala El Salvador Honduras Nicaragua Costa Rica Panama

0.36 34.98 50.75 46.55 53.62 43.11 55.21

49.64 65.02 49.25 53.45 46.38 56.89 56.89

99.60 87.34 86.30 89.00 88.26 99.47 86.75

62.70 47.91 16.70 63.20 14.43 81.44 76.15

70.90 94.72 85.76 93.98 93.00 88.76 98.65

25.30 70.31 50.38 49.50 56.00 97.13 86.54

Modified from Chapter 4 in S. Ahuja, J.B. de Andrade, D. Dionysiou, K.D. Hristovski, B. Loganathan, Water Challenges and Solutions on a Global Scale, American Chemical Society, Washington, DC, 2015.

2.6 Solutions to Global Water Challenges Over 80% of the consumed water worldwide is not collected or treated. This situation has to change because we do not have an unlimited supply of safe water for our needs; and water reclamation is absolutely necessary [28]. Discussed below are solutions to water challenges in various parts of the world.

2.6.1 Addressing Water Scarcity Challenges in the Middle East The Middle East hosts 15 of the 18 countries around the world that are at extreme risk of water scarcity (see more details in Chapter 10 in Ref. [1]). This risk arises from a combination of the natural environmental and socioeconomic drivers and their related pressures. In the Middle East, the annual volume of renewable water resources is less than 200 m3 per capita compared to nearly 100,000 m3 in Canada, 7400 m3 in continental United States, about 3500 m3 in France, and 2500 m3 in the United Kingdom. Further, in the region, as a whole, drought is a constant threat, causing considerable loss in economic and human terms. On the other hand, the growing population and the economies add pressures on available surface and groundwater resources that have to be abstracted at a greater pace in order to meet the demand of domestic uses, agriculture, and industries. As a consequence, in the Middle East together with North Africa, the rivers are among the most heavily dammed in the world. Because water availability from the rivers is too small, groundwater is overexploited. The increasing water demand, together with climate change prospects, severely threatens the regional landscape, cultural heritage, food security, development, and prosperity. The water problem in the dry regions has deepened and became more critical. Water abstraction in Egypt, Israel, Jordan, Libya, Malta, Gaza Strip, and Syria is close to or exceeds the yearly volume of renewal resources, as measured by the Water Exploitation Index. The recent drought has caused more than 800,000 people in Eastern Syria to lose their livelihoods and to face

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extreme hardship (The New York Times, March 2, 2010). Under low replenishment regimes, seawater intrusion in coastal aquifers and brackish water bodies in inland aquifers contribute to high salt concentrations of water bodies, adding to the percolation of effluents from municipal and industrial treatment plants, agricultural runoffs, and leachate from solid waste landfills which enhance the degradation of the groundwater quality. The influx of nitrate and chloride salts and other contaminants render the water unfit for drinking (Israel Hydrological Service, 2008). Water Demand Management (WDM) employs a set of complementary policy options including regulatory, economic, technical, and educative measures to address water scarcity and drought conditions. The key principles of WDM can be summarized as follows: • • • •

• • • • • •

Institutional coordination between ministries involved in the management of water resources. Integration of the various policies (water and sector policies). Legal framework, addressing issues of water as a public property, detaching land rights from water rights. To ensure access to a sufficient, safe, and regular supply of water to satisfy personal and domestic needs, and no individual shall be deprived of the minimum essential amount of water. Respect the principles of nondiscrimination and the right of individuals and groups to participate in decision-making processes. Involvement of the users in water resources planning and management, integration of social considerations. Adequate use of economic instruments. Public awareness of the need for water saving. Qualified staff in charge of water management. Financial capacity to induce the implementation of the national plans for an integrated management of water resources and water demand.

Desalination is recognized as another option to produce freshwater required to satisfy domestic water demand, especially where other alternatives to augment water supplies are not available or have grown to be more expensive than desalination. However, cost considerations still remain a significant deterrent.

2.6.2 Critical Water Issues and Solutions in Africa Water scarcity, purity, and delivery have become major challenges, especially in Africa (see more details in Chapter 6 in Ref. [1]). On this continent, 325 million people lack access to safe water. The majority of those who lack water live in rural areas. Africa is home for 15% of the global human population and has only 9% of global renewable water resources. Most of

Global Water Challenges and Solutions 29 Africa’s surface water has become polluted by human activities, and its wells are rapidly becoming dry. Impacts of climate change and climate variability are making water scarcity even more stressful. Technologies used for water harnessing are outmoded and inefficient. African countries need to modernize water purification technology; it is essential that these countries adopt new methods like roof, pavement, and urban water catchment to recharge its declining groundwater level. Provision of safe drinking water policy needs to change from piped water in every home to appropriate water-use technology in every home. Some potential new technologies still require further research. This chapter highlights some of the recent developments of nanomaterials that give promise to future water purification trends. Similarly, small-scale water harnessing technologies are outlined for groundwater recharge and drinking water purification. Design of water education in African nations can be greatly improved (is reviewed, and specific steps for improvement are given). Water purification systems that improve drinking water at the point of use are a good fit in many areas. In Kenya, Bolivia, and Zambia, water purifiers have been shown to reduce diarrheal disease by 30%–40%.

2.6.3 Addressing Water Usage in China According to a 2012 Ministry of Water Resources of the People’s Republic of China, China Water Resources Bulletin 2011 (China Water & Power Press, 2012), a closer look at how water is used shows that this problem is tractable. Almost two-thirds of municipal water is used by industry, agriculture, and construction. Households consume the remaining one-third (365 million people used 15.3 billion tons of water in 2011). Of that, laundry, bathing, and dishwashing take up the most (together more than 80%). Cooking and drinking use just over 2% (1.1 billion tons). In other words, most household water does not need to be drinkable. Bringing a large developing country such as China up to the same standards as a developed country will require more intensive water treatment. This has environmental consequences. In Jiangsu province, for example, carbon dioxide emissions increased by 28% in 2012 when a type of water filtration called ozone-biological activated carbon treatment was extended to onequarter of the provinces’ supply (5.3 million tons per day). China and other developing countries need cheap, energy-efficient methods of water purification that minimize chemical use. Fewer than 5% of Chinese homes currently have these purifiers, despite a unit’s low cost of only around 1500–2000 renminbi. China’s water-purification industry is growing by about 40% a year—fewer people are buying water dispensers and barreled water. But water-purification devices are unregulated. Incomplete after-sales service leads to improper maintenance, and delays in changing filter cartridges can introduce microorganisms. Filters and units made from toxic materials such as nonfood-grade plastic are ineffective.

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Treated gray water (wastewater from showers and baths) and black water (from toilets) are increasingly used in China for industrial and irrigation purposes, and for flushing toilets in new residences. But this type of recycling is impractical for most existing households because of the high cost and the disruption in the home while installing the necessary plumbing. It has been suggested that by using cheap, low-carbon water purifiers in all homes, China can avoid the technology “lock-in” that leads developed countries to waste potable water, and China can leapfrog to a sustainable supply system. In the long term, the improvement in water sources will ensure that most people have safe drinking water.

2.6.4 Technological Solutions to Water Challenges in India The problems associated with water usage can be broadly grouped as (a) inadequate availability of water, (b) poor quality of water for its intended use, and (c) indiscriminate use of this valuable natural resource (see more details in Chapter 9 in Ref. [1]). The technological approaches for solving the problems can therefore emanate from recovering water from sustainable resources, augmentation of quality of water from available and accessible sources, and renovation for recycling. Technology missions on winning, augmentation, and renovation for water (WAR) was initiated in 2009 to address the water challenges following three-pronged technological approaches stated by the Union Ministry of Science and Technology. The mission emphasizes problem-solving approaches and focuses on applications research in view of urgency of the solutions required. The major challenges facing the country were identified to mount research-based solutions. Roping in solution providers and stakeholders to address water challenges through meeting technical and economic benchmarks with a well-defined revenue model was a novel experiment. The initiative also promoted developmental research for designing and developing low cost solutions for domestic use of safe drinking water, referencing of technologies in social context, capacity building of water managers, and encouraging new research ideas. Bilateral and multilateral innovation cooperation was developed to promote joint R&D as well as deployment of innovative solutions for treatment of drinking water, wastewater treatment, and contaminant detection. Capacity building programs for sustainable rainwater harvesting and groundwater recharge programs which included rooftop rainwater harvesting, rainwater harvesting in paved and unpaved areas, and rainwater harvesting in lakes and tanks evinced interest not only from Indian provinces (states) but also from several developing countries, and training programmers were conceptualized and implemented for participants from 15 developing countries. The mission and related activities have so far addressed 19 water challenges in 25 clusters directly benefiting 212 villages from 23 states. A majority of the pilot systems are since commissioned, providing safe drinking water to nearly 1.56 million people. As an output of

Global Water Challenges and Solutions 31 mission activities, several technology-led solutions to water-related problems have emerged, which has resulted in perceptible improvement in water availability and water quality scenario at the location of pilot trials. These cost-effective and efficient interventions have resulted in significant improvements in drinking water availability and quality and augmentation of water resources through wastewater treatment. The benefits include improved access to water, improved health, sensitized local community to water issues, and improved capacity of the community for operation and maintenance of the pilot system.

2.6.5 Overcoming Water Treatment Challenges in Small Developing Countries in Europe Many developing countries face unique water treatment challenges and barriers because the communities do not have a well-established socioeconomic, educational, and technological infrastructure, which is capable of supporting conventional water treatment solutions (see more details in Chapter 12 in Ref. [1]). It is not uncommon for many proposed and implemented water treatment solutions to fail in the developing countries, especially in small, impoverished, and rural communities. It is desirable to examine underlying factors that contribute to water treatment challenges and barriers in developing world communities and propose a systems approach for developing a sustainable water treatment solution in small, rural, and impoverished communities. Five different categories of challenges and barriers to water treatment solutions in developing countries can be identified: economics-driven factors; knowledge-based factors; sociocultural implications; adequacy of supporting infrastructure; and environmental specifics. A systems approach, which stems from the need to resolve these challenges, is elucidated in an attempt to minimize the failure rate of implementing inadequate water treatment solutions in small, rural, and impoverished communities of the developing world. A road map that illustrates a systems approach to water treatment solutions in developing countries can incorporate several nonsequential stages that could easily be addressed by bridging the water quality data gap and characterizing the environment; understanding the local needs and capabilities; developing an engineering solution; developing a management platform; and creating a sustainable education. Each stage necessitates inputs from a variety of disciplines and creation of multidisciplinary teams to address the challenges and barriers that may exist. The Republic of Serbia is an example of a developing country with a water management system that has not adequately transitioned to address the need of the new socioeconomic paradigm (see more details in Chapter 13 in Ref. [1]). The water resources management system in Serbia was examined through the prism of regulations, management, engineering, and education, which represent principal pillars of every national socioeconomic system. This study shows that an in-depth analysis of the existing situation and identification of barriers represent the initial steps in the process of developing and implementing an integrated national water management

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system. To introduce a sustainable water treatment solution into a developing world community, only technologies that are inexpensive to construct and simple to operate should be considered for implementation. These technologies have to be energy-independent and efficient because of an unreliable or nonexistent energy supply and infrastructure. Providing sustainable long-term support for these technologies could be achieved by creating community businesses that would manufacture these treatment systems or their components using locally available resources. This social-entrepreneurship platform would need to be further supplemented by technical training that focuses on manufacturing, operation, performance monitoring, and maintenance of these systems. Creation of such platforms, which are based on synergy between social-entrepreneurship and technical capacity building, would inevitably minimize the system failure rates because these two elements represent the major factors that contribute to collapse of system-oriented solutions in developing countries.

2.6.6 Drinking Water in Central America The advantages and disadvantages of the centralized and noncentralized systems are presented in Table 2.3, based on a review of plausible alternatives for water treatment that aim to improve the population’s health in Central American countries (see more details in Chapter 4 in Ref. [1]). These options can be applied worldwide.

2.6.7 Solutions for Advanced Countries The advanced countries such as the United States have a different set of problems. The sources of water contamination are many and varied—the fact is we risk greater chances of pollution as we try to improve our quality of life. If adequate steps are not taken to monitor water quality at point- and nonpoint-sources of pollution, we are bound to encounter problems. In addition, when a change is made in the source of water supply, as exemplified by Flint Michigan, it is important to fully evaluate the impact of such changes instead of just looking at economic advantages. It has necessitated upgrading of infrastructure that requires eliminating lead pipes. This is a very costly approach that is going to cost billions of dollars. Various industries need to monitor their waste streams to assure no harmful pollutants are being added to the water resources. GenX contamination of Cape Fear River water by Chemours which affected several counties in the Wilmington, NC, area clearly demonstrated this point. To correct this problem, Chemours is now collecting their wastewater and processing it elsewhere. In general, wastewater treatment plants need to carefully monitored so that the processed water they add back into water resources does not contain drugs from human and veterinary use. The fact is wastewater can be treated to a point where it is perfectly safe to drink—the only prohibitive factor is cost. Singapore is using this approach.

Global Water Challenges and Solutions 33 Table 2.3 A review of the point-of-use technologies proposed for Central America Technology GFU

Solar distillation

Solar disinfection

Chlorination

Countertop UV disinfection

Main Advantages

Main Disadvantages

Implementation Sites

Small settlements spread No replacement cost over large area; lowreported; it may need income settlements that periodical major lack access to basic maintenance; no services (i.e., electricity, information on the piped water) minimum water quality required; field tests must be carried out to assess its performance Requires a significant Reported as highly Widely tested in field; can amount of solar applicable in semiarid remove microorganisms radiation; depending on regions; small settlements and organic and inorganic pollutants (i.e., the design it may have low with high amount of solar efficiency. radiation heavy metals, VOCs); provides cost-effective safe water Requires important dose Point-of-use technology; Highly cost-effective; it may be applied in both of solar UV radiation; widely tested in field rural or urban microorganisms rework; many different growth may occur if is not communities; tested in approaches reported; field work for many properly applied; use of different conditions recommended PET bottles may produce cross-contamination Highly cost-effective, Ineffective against certain Small settlements spread over large area, lowrelatively easy to monitor, pathogens, overdosage is income settlements field tested common and may lead to lacking access to basic taste, odor and services (i.e., electricity, disinfection by-products piped water) Peri-urban or rural Moderate to high cost, Designed for household communities with access requires electricity, use, highly effective to electricity maintenance of the UV against a wide spectrum lamp required. of microbial pathogens, easy to operate, no formation of known DBPs, field tested Designed for household use; specific for people with low income; no power inputs required; capable of meeting international standards for microbiological quality

DBP, disinfection by-products; GFU, gravity-fed ultrafiltration. Modified from Chapter 4 in S. Ahuja, J.B. de Andrade, D. Dionysiou, K.D. Hristovski, B. Loganathan, Water Challenges and Solutions on a Global Scale, American Chemical Society, Washington, DC, 2015.

2.7 Remediating Arsenic Contamination of Groundwater Worldwide When arsenic gets into water by any of a variety of ways, it becomes a major problem. Arsenic contamination of groundwater has been reported in a large number of countries in the world; Bangladesh and Bengal (India) suffer the most. Almost 100 million people in Bangladesh are at

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risk, as they consume arsenic-contaminated water at levels of 10 ppb or greater. Inorganic arsenic above 10 ppb level can increase the risk of lung, skin, bladder, liver, kidney, and prostate cancers. Water contamination in Bangladesh and India has been attributed to the geology in parts of those countries. Microbially mediated reduction of assemblages comprising arsenic sorbed to ferric oxyhydroxides is gaining consensus as the chief mechanism for the mobilization of arsenic into groundwater. A recent microcosm-based study has provided the first direct evidence for the role of indigenous metal-reducing bacteria in the creation of toxic, mobile As(III) in sediments from the Ganges Delta [2]. It should be noted here that arsenic contamination from other sources is possible worldwide because arsenic compounds are used commercially for the following applications: • • • • •

pesticides: monosodium methyl arsonate, disodium methyl arsonate; insecticide: dimethylarsenic acid; aquatic weed control and sheep and cattle dip: sodium arsenite; defoliating cotton bolls: arsenic acid, arsenic pentoxide; some pharmaceuticals and decolorizing glass: arsenic trioxide.

Large areas in the West, Midwest, and Northeast US have high arsenic concentrations. For example, in North Carolina, arsenic was found in 960 wells statewide in January 2000. According to the Wilmington Star News of August 18, 2003, half of the state’s population depends on groundwater. The state toxicologist, Ken Rudo said “for new wells, arsenic test is pretty much not done.” A number of methods can be used for analyzing arsenic in water at 10 ppb or an even lower level [2]. The speciation of arsenic requires separations based on solvent extraction, chromatography, and selective hydride generation (HG). Detection limits for arsenic down to 0.0006 μg/L can be obtained with inductively coupled plasma mass spectrometry (ICPMS-I). High-performance liquid chromatography coupled to inductively coupled plasma-mass spectrometry (HPLC CP-MS) is currently the best technique available for the determination of inorganic and organic species of arsenic. The main problem is the high cost. Using HG, arsenic can be determined by a relatively inexpensive atomic absorption spectrometer or atomic fluorescence spectrometer (AFS) at single-digit μg/L. For developing countries, there is a need for low-cost and reliable instrumentation and dependable field test kits. The following methods can be used for remediation of arsenic contamination of water: • • • •

coagulation with ferric chloride or alum sorption on activated alumina sorption on iron oxide–coated sand particles granulated iron oxide particles

Global Water Challenges and Solutions 35 • • • • • • • •

polymeric ligand exchange nanomagnetite particles hybrid cation exchange resins hybrid anion exchange resins polymeric anion exchange reverse osmosis nanomagnetite particles sand with zero valent iron

Two filters that stand out in terms of their usefulness for serving a small family or a community are briefly described below.

2.7.1 Single-Family System This system is based on solid sorbents to obtain potable water. Special emphasis has been placed on iron-based filters because they appear to be chemically most suitable for arsenic removal, they are easy to develop, and are environmentally benign. Arsenic removal mechanisms for a SONO filter are based on surface complexation reactions, sorption dynamics, and kinetics (see details in Chapter 12 in Ref. [4]). This is one of the four filters approved by the Bangladesh government for public use. The manufacturer claims that the filtered water meets Bangladesh standards (50 ppb of arsenic; 10 ppb standard in the United States), has no breakthrough, works without producing toxic wastes; these figures are based on EPA guidelines. This filter costs about $40, lasts for 5 years, and produces 20–30 L/h for daily drinking and cooking needs of one or two families. A large number of these filters have been used all over Bangladesh and continue to provide more than a billion liters of safe drinking water. This innovation was recognized by the National Academy of Engineering Grainger Challenge Prize for Sustainability, with the highest award for its affordability, reliability, ease of maintenance, social acceptability, and environmental friendliness. It should be noted that the flow rate may decrease 20%–30% per year if the groundwater has high iron levels (>5 mg/L) because of the formation and deposition of natural hydrous ferric oxide (HFO) in sand layers. The sand layer (about 1-inch thick) then has to be removed, washed, and reused, or replaced with new sand. A protocol for elimination of pathogenic bacteria should be used once a week in areas where coliform counts are high. It should be noted that, as with all commercial filters, the consumer needs to be alert to manufacturing defects, and mishandling during transportation.

2.7.2 Community-Based Filters A community filter can serve about 200 households and requires no chemical addition, pH adjustment, or electricity (see Chapter 13 in Ref. [2]). A large number of these filters have been installed in India since 1997, and have the following characteristics:

36 • •

Chapter 2 Utilize activated alumina as an adsorbent media that can be regenerated. Purify influent arsenic solutions ranging from 100 to 500 μg/L, containing both As(III) and As(V) species.

When the filter is exhausted, the media can be replaced and the spent media is then taken to a central regeneration facility for further reuse. An arsenic-laden spent regenerant form is converted to a small volume of sludge that can be contained in an aerated, coarse sand filter. The process is claimed to be environmentally sustainable because the treatment residues are not toxic under normal environmental conditions. It is also economically sustainable, as the villagers collectively maintain the units by paying a monthly water tariff of about $0.40. Some of the promising technologies for water purification are discussed below.

2.8 Promising Technologies Several promising technologies are discussed below. The cost of application of these technologies may be a deterrent for some countries.

2.8.1 Water Desalination Two basic types of technologies have been widely used to separate salts from ocean water: thermal evaporation and membrane separation reverse osmosis (RO). Of the two technologies (for more details see Chapter 19 in Ref. [1]), RO emerged as the most suitable technology (see Chapter 10 in Ref. [1]) to build flexible and modular plants to desalinate brackish and seawater RO desalination plants (SWRO). The SWRO has gained momentum and currently dominates desalination markets outside of the Arabian Gulf where thermal evaporation is still the desalination technology of choice (mainly because of access to low-cost fuel and cogeneration of power and water). The SWRO technology is well established and considered the least energy-intensive desalination technology. Increased market competition and technological improvements including improved RO membranes with higher salt rejection, high efficiency of pumps and motors, and efficient energy recovery devices (ERDs) have dramatically reduced the cost of water produced in SWRO. The cost of energy (60% of the operation costs) is relatively high, fueling the general water industry’s perception that seawater desalination industry is inadequately viable. However, manipulation of the plant operation and water production at off-peak hours may yield a significant saving in the cost of energy. As of 2013, desalination plants operated worldwide and produced more than 80 million cubic meters (MCM) per day. In Australia, the most important desalination plants are located in Perth and Sydney, and the two plants were designed to produce about 250,000 m3/day and above. Improvements in design, management, the scale of equipment, and pre- and posttreatment have been as important as improvements in the core RO technology, leading to a fall in desalination

Global Water Challenges and Solutions 37 Table 2.4 Cost of producing water by desalination Desalination Facility

Production (m3/year)

Cost ($US/m3)

Lymassol, Cyprus Hamma, Algeria Larnaca, Cyprus Perth, Australia Skikda, Algeria Point Lisas, Trinidad Tampa Bay, Florida Hadera, Israel Tenes, Algeria Palmachim, Israel Mactaa, Algeria Sorek, Israel Ashkelon, Israel

13 66 18 46 33 39 31 127 66 30 165 150 108

1.18 0.82 0.76 0.75 0.73 0.70 0.67 0.60 0.59 0.55 0.55 0.53 0.52

Modified from Chapter 19 in Ref. S. Ahuja, J.B. de Andrade, D. Dionysiou, K.D. Hristovski, B. Loganathan, Water Challenges and Solutions on a Global Scale, American Chemical Society, Washington, DC, 2015.

prices over the past decades. The cost of producing water by desalination is illustrated in Table 2.4. In Israel, desalination of brackish water and seawater has now reached a production capacity of more than 600 million m3 year1, equal to about 90% of the current domestic consumption. The plan is to be gradually extended to 750 MCM by 2020 and to 1600 MCM per year by 2040 to allow a reliable supply with a probability of 95%. Of the total 6200 million m3 year1 that will be required to meet the demand of Israel, Palestine, and Jordan by 2040, 25% will be produced from seawater desalination (1600 million m3 year1). Desalination of seawater impacts the environment at many different levels, starting at the location of desalination plants close to the seacoast, the construction of deep intake and brine and backwash outfall, the use of cleaning chemicals, and the need for a major power supply requiring the erection of independent power plants. The desalination plants affect the local biodiversity in the ecologically sensitive coastal areas, contribute to greenhouse gas emissions, discharge concentrated saline waste, causing a buildup of the chemicals that threaten the fragile marine ecosystem. A desalination plant producing 100 million m3 year1 of desalinated water discharges up to 535 tons per year of Fe and 40 tons per year of P and brine containing 73.5 g L1 of salts, double the seawater background level. High energy consumption is also associated with the need to remove boron in the permeate, which requires a second filtration pass that increases the overall energy consumption. To alleviate some adverse environmental impacts, the desalination plants are built close to power plants to be able to blend the brine discharge with the power plant cooling water or use diffusers to achieve a rapid mixing with the entire water column, resulting in lower salinity and a lower temperature. The offshore seawater intakes are built as submerged structures with slow intake velocity to avoid interference with aquatic life. Further work on risk and impact assessment is still necessary, leading to improved

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membranes, having a longer life expectancy, higher flux as well as nanomembranes, carbon nanotubes, membrane distillation, and increased energy efficiency.

2.8.2 Nanotechnology Solutions for Global Water Challenges The rapid and continued growth in the area of nanomaterial-based devices offers significant promise for addressing future water quality challenges (Chapter 18 in Ref. [1]). Meager availability of clean and safe drinking water is responsible for more deaths than war, terrorism, and weapons of mass destruction combined. This suggests that contaminated water poses a significant threat to human health and welfare. Additionally, standard water disinfection approaches such as sedimentation, filtration, and chemical or biological degradation are not fully capable of destroying emerging contaminants (e.g., pesticides and pharmaceutical waste products) or certain types of bacteria (e.g., Cryptosporidium parvum). Nanomaterials and nanotechnology-based devices can potentially be employed to solve the challenges posed by various contaminants and microorganisms. Nanomaterials of different shapes, namely nanoparticles, nanotubes, nanowires, and fibers, have the ability to function as adsorbents and catalysts. They have an expansive array of physicochemical characteristics, making them highly attractive for the production of reactive media for water membrane filtration, a vital step in the production of potable water. As a result of their exceptional adsorptive capacity for water contaminants, grapheme-based nanomaterials have emerged as a subject of significant importance in the area of membrane filtration and water treatment. Also, advanced oxidation processes, with or without sources of light irradiation or ultrasound, have been found to be a promising option for water treatment at near ambient temperatures and pressures. Furthermore, the uses of visible light–active titanium dioxide photocatalysts and photo-Fenton processes have shown a significant potential for water purification. A wide variety of nanomaterial-based sensors, for monitoring water quality, are also reviewed in detail.

2.9 Conclusions Water availability, impact of climate disruptions, and monitoring water quality have been covered in this chapter. Numerous challenges are encountered to provide drinking water globally. It is certainly time for the government and related agencies to take a serious look at water quality issues and to take necessary corrective steps without delay. Various solutions are provided to global water challenges in the Middle East, Africa, China, India, small developing countries in Europe, Central America, and advanced countries like the United States. In addition, simple solutions to arsenic contamination of water worldwide have been provided. Promising advanced technologies such as desalination and nanomaterials have been discussed to help us address a number of issues relating to water purification.

Global Water Challenges and Solutions 39

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