<P> The removal of pathogens from recycled water is of high priority because wastewater always contains pathogens capable of infecting humans . The levels of pathogenic viruses have to be reduced to a certain level in order for recycled water to not pose a threat to human populations . Further research is necessary to determine more accurate methods of assessing the level of pathogenic viruses in treated wastewater . </P> <P> Wasting of water (also called "water waste" in the U.S.) is the flip side of water conservation and, in household applications, it means causing or permitting discharge of water without any practical purpose . Inefficient water use is also considered wasteful . By EPA estimate, household leaks in the U.S. can waste approximately 900 billion gallons (3.4 billion cubic meters) of water annually nationwide . Generally, water management agencies are reluctant or unwilling to give a concrete definition to the somewhat fuzzy concept of water waste . However, definition of water waste is often given in local drought emergency ordinances . One example refers to any acts or omissions, whether willful or negligent, that are "causing or permitting water to leak, discharge, flow or run to waste into any gutter, sanitary sewer, watercourse or public or private storm drain, or to any adjacent property, from any tap, hose, faucet, pipe, sprinkler, pond, pool, waterway, fountain or nozzle .". In this example, the city code also clarifies that "in the case of washing, "discharge," "flow" or "run to waste" means that water in excess of that necessary to wash, wet or clean the dirty or dusty object, such as an automobile, sidewalk, or parking area, flows to waste . Water utilities (and other media sources) often provide listings of wasteful water - use practices and prohibitions of wasteful uses . Examples include utilities in San Antonio, Texas . Las Vegas, Nevada, California Water Service company in California, and City of San Diego, California . The City of Palo Alto in California enforces permanent water use restrictions on wasteful practices such as leaks, runoff, irrigating during and immediately after rainfall, and use of potable water when non-potable water is available . Similar restrictions are in effect in the State of Victoria, Australia . Temporary water use bans (also known as "hosepipe bans") are used in England, Scotland, Wales and Northern Ireland . </P> <P> Strictly speaking, water that is discharged into the sewer, or directly to the environment is not wasted or lost . It remains within the hydrologic cycle and returns to the land surface and surface water bodies as precipitation . However, in many cases, the source of the water is at a significant distance from the return point and may be in a different catchment . The separation between extraction point and return point can represent significant environmental degradation in the watercourse and riparian strip . What is "wasted" is the community's supply of water that was captured, stored, transported and treated to drinking quality standards . Efficient use of water saves the expense of water supply provision and leaves more fresh water in lakes, rivers and aquifers for other users and also for supporting ecosystems . A concept that is closely related to water wasting is "water - use efficiency ." Water use is considered inefficient if the same purpose of its use can be accomplished with less water . Technical efficiency derives from engineering practice where it is typically used to describe the ratio of output to input and is useful in comparing various products and processes . For example, one showerhead would be considered more efficient than another if it could accomplish the same purpose (i.e., of showering) by using less water or other inputs (e.g., lower water pressure). However, the technical efficiency concept is not useful in making decisions of investing money (or resources) in water conservation measures unless the inputs and outputs are measured in value terms . This expression of efficiency is referred to as economic efficiency and is incorporated into the concept of water conservation . </P>

What are the methods of conservation of water