Almost 29% of the world's population lack access to safe drinkable water with a projected increase to 43% in 2050. Water scarcity due to an increasing demand for clean water and diminishing supply is a global reality, with factors such as flooding, climate change, pollution and increase in population contributing to a decline in the quantity and quality of water.
Water reuse is the use of treated wastewater for beneficial purposes. Associated terms are wastewater reuse and water recycling. Water reuse augments existing water supply, and for communities experiencing water shortage, water reuse means extensive increment and an alternative source of clean water. Water reuse helps reduce wastewater discharge and as such minimizes or eliminates pollution. It reduces water over-abstraction, and eventually water stress. Water recycling results in a sustainable source of reliable and dependable water supply that is not affected by external factors like drought or variability in weather.
Water reuse processes now tend towards managing wastewater as a resource instead of a waste. Wastewater treatment processes include preliminary, primary and secondary steps. Preliminary steps include measuring the flow coming into the plant, screening out large solid materials, and grit removal. Primary treatment targets settleable matter and scum that floats to the surface. Secondary treatment processes are employed to remove total suspended solids and dissolved organic matter. Secondary treatment processes consist of aerated activated sludge basins followed by final solids separation via settling or membrane filtration and disinfection.
Three types of wastewater treatment projects exist:
Nonpotable reuse projects treat wastewater for purposes other than consumption, such as irrigation, industrial use, and agriculture. Nonpotable reuse systems usually have lower water quality objectives than potable systems, and the level of treatment varies depending on the end use.
Potable reuse systems use advanced treatment processes to remove contaminants from so that is hygienic enough for consumption and to meet drinking water standards and other appropriate water quality objectives. Commonly, the highly treated water is then released into a surface water body or aquifer, then withdrawn, treated further, blended with other conventional water supply sources, and piped for the end users.
De facto reuse occurs when a community draws water from a water body that includes wastewater from upstream communities. De facto reuse is quite common and occurs unintentionally. The movement of water downstream serves to filter it and as such make it relatively hygienic.
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