Learning Objectives
• Determine water requirements for different uses, communities, and future populations
• Define consumptive and non-consumptive uses of water
• Cite appropriate standards for different uses of water and determine minimum water requirements
• Describe how scale affects quantification of water use
• Describe differences in water use and supply in rural and urban communities in India
• Model available population data to forecast future populations in different communities
• Justify the use of different population forecasting methods for different conditions
• Quantify seasonal and daily variations in water demand for design of water supply systems
Water is the most important requirement for sustaining life. Design of water supply systems requires that the water source be adequate in terms of quantity, quality and sustainability. Design of wastewater systems requires knowledge of water quantities used and treatment standards to be achieved. This chapter deals with the different uses of water and how much needs to be supplied at a minimum.
Figure 2.1 shows the flow of water through water supply and wastewater systems for any given location, e.g., a city, town, or small community. Water is extracted from a groundwater or surface water resource and is taken for treatment to a water treatment plant. The degree of treatment provided depends on the quality of the raw water. After treatment, the water is sent into the distribution system from where it reaches individual consumers. These consumers may be single households, apartment buildings, offices, industries or factories, commercial or business establishments, or any other place where clean water is required.
After use, the discarded water is termed ‘wastewater’ and in general, it goes into drains in sewered communities. The wastewater in sewerage systems is taken for treatment to a wastewater treatment plant. After treatment, the wastewater is discharged on land or in the sea, or it can be reused for horticulture, irrigation, industrial uses, and cleaning activities depending on the degree of treatment provided. Where drainage or sewerage systems are not present, the wastewater may be drained into cess pits, septic tanks, or reused after providing some treatment.
DESIGN OF WATER SUPPLY SYSTEMS
The most important task in the design of water supply systems is identification of an appropriate source of water.
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