“Thousands have lived without love, not one without water.” — W.H. Auden, poet
October means football season, pumpkin lattes, Halloween costumes and many other fun seasonal changes. While we’re excited for all things autumn, here at the Waterworld USA we’re welcoming this new month for another reason. In September 1991, President George Bush declared October as National Energy Awareness Month, encouraging government and organizations to raise awareness of the importance of sustainably managing the nation’s energy resources. Recognizing the significance of the energy-water nexus, the Department of Energy has chosen to dedicate this year’s campaign to promoting both energy and water conservation. Energy and water are highly connected and there is ample opportunity to reduce waste of both resources. During this month of energy conservation awareness, it is worth reflecting upon global water supply, the need for water reuse, water treatment operations, efforts to regulate water, clean water legislation, water safety and the interdependence of energy and water.
The current world population of ~7 billion is expected to reach 9.5 billion by 2050. More people, of course, means increased need for more potable water. In addition to the increasing need to meet potable water supply demand and other urban demands (e.g., landscape irrigation, commercial, and industry needs), increased agricultural demands due to greater incorporation of animal and dairy products into the diet has also increased demand on water for food production. These increases in population and a dependency on high-water-demand agriculture are coupled with increasing urbanization, and all of these factors and others are producing land use changes that exacerbate water supply challenges.
With the growing population trend and settlement of humans in areas that were previously unoccupied and considered pristine, drinking water has become a limiting factor. In order to consume water from such a freshwater source and not get sick, the water has to be treated; the contaminants must be removed. This is where conventional water treatment (with disinfection), including filtration and sometimes reverse osmosis (RO) systems, comes into play. Such treatment can remove these contaminants and prevent users of the water from contracting waterborne illnesses.
Water reuse through mechanisms such as reverse osmosis is integral to sustainable water management because it allows water to remain in the environment and to be preserved for future uses while meeting the water requirements of the present. Water and energy are interconnected, and sustainable management of either resource requires consideration of the other. The energy required for capturing, treating, and distributing water and the water required to produce energy are inextricably linked. Water reuse can achieve two benefits: offsetting water demand and providing water for energy production. Thermoelectric energy generation uses about half of the water resources consumed in the US and is a major potential user of reclaimed water.
Reuse projects must factor in climate predictions, both for demand projections and for ecological impacts. Municipal wastewater generation in the United States averages approximately 75 gallons per capita daily (gpcd) and is relatively constant throughout the year. As urban areas continue to grow, pressure on local water supplies will continue to increase. Reuse will continue to increase as the world’s population becomes increasingly urbanized and concentrated near coastlines, where local freshwater supplies are limited or are available only with large capital expenditure.
Municipal water treatment operations and associated treatment unit processes are designed to provide reliable, high-quality water service for customers and to preserve and protect the environment for future generations. At its simplest level, the basic goal of water treatment operations is to protect public health, with a broader goal to provide potable and palatable water. The bottom line is that the water treatment process functions to provide water that is safe to drink and is pleasant in appearance, taste, and odor.
Many water treatment unit processes are commonly used today. The treatment processes used depend on the evaluation of the nature and quality of the particular water to be treated and the desired quality of the finished water. For water treatment unit processes employed to treat raw water, one thing is certain: As new U.S. Environmental Protection Agency (USEPA) regulations take effect, many more processes will come into use in an attempt to produce water that complies with all current regulations, despite source water conditions.
The effort to regulate drinking water and wastewater effluent has increased since the early 1900s. Beginning with an effort to control the discharge of wastewater into the environment, preliminary regulatory efforts focused on protecting public health. The goal of this early wastewater treatment program was to remove suspended and floatable material, treat biodegradable organics, and eliminate pathogenic organisms. Thus, regulatory efforts were directed toward constructing wastewater treatment plants in an effort to alleviate the problem. But a problem soon developed: progress. Progress in the sense that time marched on and with it so did proliferation of city growth in the United States, where it became increasingly difficult to find land required for wastewater treatment and disposal.
Wastewater professionals soon recognized the need to develop methods of treatment that would accelerate nature’s purification of water under controlled conditions in treatment facilities of comparatively smaller size. Regulatory influence on water quality improvements in both wastewater and drinking water took a giant step forward in the 1970s. The Water Pollution Control Act Amendments of 1972 (Clean Water Act) established national water pollution control goals. At about the same time, the Safe Drinking Water Act (SDWA) passed by Congress in 1974 was designed to maintain and protect the public drinking water supply.
Clean Water Act
In 1972, Congress adopted the Clean Water Act, which established a framework for achieving its national objective “to restore and maintain the chemical, physical, and biological integrity of the nation’s waters.” Congress decreed that, where attainable, water quality “provides for the protection and propagation of fish, shellfish, and wildlife and provides for recreation in and on the water.” These goals are referred to as the “fishable and swimmable” goals of the Act. Before the CWA, no specific national water pollution control goals or objectives existed. Current standards require that municipal wastewater be given secondary treatment. The goal, via secondary treatment (i.e., the biological treatment component of a municipal treatment plant), was set so the principal components of municipal wastewater—suspended solids, biodegradable material, and pathogens—could be reduced to acceptable levels.
Industrial dischargers are required to treat their wastewater to the level obtainable by the best available technology (BAT) for wastewater treatment in that particular type of industry. Moreover, a National Pollutant Discharge Elimination System (NPDES) program was established based on uniform technological minimums with which each point source discharger must comply. Under NPDES, each municipality and industry discharging effluent into streams is assigned discharge permits. These permits reflect the secondary treatment and BAT standards. Water quality standards are the benchmark against which monitoring data are compared to assess the health of waters to develop total maximum daily loads in impaired waters. They are also used to calculate water-quality-based discharge limits in permits issued under NPDES.
Safe Water Drinking Act
The Safe Drinking Water Act (SDWA) of 1974 mandated the U.S. Environmental Protection Agency (USEPA) to establish drinking water standards for all public water systems serving 25 or more people or having 15 or more connections. Pursuant to this mandate, the USEPA established maximum contaminant levels for drinking water delivered through public water distribution systems. The maximum contaminant levels (MCLs) of inorganics, organic chemicals, turbidity, and microbiological contaminants are shown in Table 6.2. The USEPA’s primary regulations are manda- tory and must be complied with by all public water systems to which they apply. If analysis of the water produced by a water system indicates that an MCL for a con- taminant is being exceeded, the system must take steps to stop providing the water to the public or initiate treatment to reduce the contaminant concentration to below the MCL.
The USEPA has also issued guidelines to states with regard to secondary drinking water standards (Table 6.3). These guidelines apply to drinking water contaminants that may adversely affect the aesthetic qualities of the water (i.e., those qualities that make water appealing and useful), such as odor and appearance. These qualities have no known adverse health effects, so secondary regulations are not mandatory; however, most drinking water systems comply with the limits. They have learned through experience that the odor and appearance of drinking water are not problems until customers complain, and one thing is certain—they will complain.
Water and Energy
Water is needed to generate energy. Energy is needed to deliver water. Both resources are limiting the other—and both may be running short. This is an important statement because most people have no idea (not even a clue) about the water–energy connection. The fact is energy efficiency and sustainability are key drivers of water reuse, which is why water reuse is so integral to sustainable water management. The water–energy connection recognizes that water and energy are mutually dependent—energy production requires large volumes of water, and water infrastructure requires large amounts of energy.
Energy production requires an enormous amount of water, ranking as the second most water consuming industry in the country. Conversely, about 90 percent of U.S. energy is generated from nuclear and fossil power plants, which require 190,000 million gallons of water per day to produce electricity, accounting for 39 percent of the nation’s freshwater withdrawals. Water conservation is thus a critical factor in slowing the compound loop of increased water and energy use witnessed in the water–energy connection.