share responsibilities through a public-private partnership. Utilities can either be in charge of only water supply and/or sanitation, or they can also be in charge of providing other services, in particular electricity and gas. In the latter case they are called multi-utilities. Bulk water suppliers are entities that manage large aqueducts and sell either treated or untreated water to various users, including utilities. Public service providers. Eighty-nine percent of Americans served by a public water system are served by a public or cooperative entity. Usually public systems are managed by utilities that are owned by a city or county, but have a separate legal personality, management and finances. Examples are the District of Columbia Water and Sewer Authority, the Los Angeles Department of Water and Power and Denver Water. In some cases public utilities span several jurisdictions. An example is the Washington Suburban Sanitary Commission that spans two counties in Maryland. Utility cooperatives are a major provider of water services, especially in small towns and rural areas Private utilities. About half of American drinking water utilities, or about 26,700, are privately owned, providing water to 11% of Americans served by public water systems. Most of the private utilities are small, but a few are large and are traded on the stock exchange. The largest private water company in the U.S. is American Water, which serves 15 million customers in 1,600 communities in the U.S. and Canada. It is followed by United Water, which serves 7 million customers and is owned by the French firm Suez Environnement. Overall, about 33.5 million Americans (11% of the population) get water from a privately owned drinking water utility. In addition, 20% of all wastewater utilities in the U.S. are privately owned, many of them relatively small. About 3% of Americans get wastewater service from private wastewater utilities. In addition, more than 1,300 government entities (typically municipalities) contract with private companies to provide water and/or wastewater services. Multi-utilities. Some utilities in the U.S. provide only water and/or sewer services, while others are multi-utilities that also provide power and gas services. Examples of utilities that provide only water and sewer services are the Boston Water and Sewer Commission, Dallas Water Utilities, the New York City Department of Environmental Protection, Seattle Public Utilities and the Washington Suburban Sanitary Commission. Other utilities, such as the San Francisco Public Utilities Commission, provide power in addition to water and sewer