Water Treatment "Part 2": Forecasting future water demand.

The volume of water required for a specific activity or person is what is known as the water demand, and its unit of measurement is cubic meters per second, it can also be measured in cubic meters per year. Wastage is often calculated as a percentage of actual demand, and aggregate demand is calculated as the sum of actual demand and wastage (QI):

QI= α ✱ Qa

Calculating the difference between the volume of water pushed and the volume of water generated yields an estimate of the water wastage. The effectiveness of the water distribution system, pipe failures, pipe obstructions, and unlawful distribution network connections are all parameters that influence the quantity of water wastage.

Water meter

Factors Influencing Individual Water Demand:

Individual water demand is impacted by certain variables, geographical regions are largely involved in most of these variables. Water consumption habits differ from one culture to another, and the climate affects greatly, as with the rise in temperatures the demand for water increases, in addition to that, the areas where water is easily available have a high water consumption. In addition to all of this, the price of water has a significant impact on individual demand, as consumption rises and the desire to save water declines as the price of water falls.

Development of Water Abstractions and Water Consumption by WaterGAP

The total average water demand for a given community is the sum of the average demand for each population group with a given water demand per capita:

Q= Σ(Popi ✱ Capi) (I/d)

When calculating the demand in the long term, in the case of developing countries, it is necessary to take into account the increase in demand for water as a result of improving access to it.
As consumption declines at night while sharply increasing in the early evening hours of summer days, there is a significant difference in water demand between day and night. Peak points in demand, or the deviation of demand for a city or region over a given period of time, develop as a result of demand variations.

Global use of freshwater. 2016 FAO data.

Along with building water delivery subsystems, water storage facilities are designed to lessen the effects of daily demand changes. The storage unit is not required when the production is equal to the hourly maximum usage.

• To calculate the average water demand, we use the following equation:

Q0= Average annual demand/ 365✱24

People usually use the toilet between halves of a football match, or prepare a pot of tea or coffee, so the time of showing a match is another peak point, and due to the concentration of people in front of the screen during the match, the amount of water consumption decreases. Cumulative error laws are produced by statistical analysis and can be used to identify poor water intake.

Forecasting process and timeframes:

In order to plan for new water supply infrastructures, future water demand must be forecast for the next 10 to 20 years. Also, when operating the treatment plant during the day, good forecasting of water use during the hours of the day must be made. Among the forecasting methods, the method of extrapolation and aggregation of water uses for each consumer group to predict the annual water use is the most detailed method and requires a lot of data. On the premise that water demand will increase or decrease with a constant growth factor, inductive interpolation is based.

demand p+n= demand p. GFn

• where:
  demand p: demand over a period of time p
  demand p+n: demand over a period of time p+n
  n: The number of years.
  GF: Population growth factor.

Determining the point at which a capacity increase is required is crucial when making plans for future water demand. The extra capacity strengthen the reliability of the water supply and enhance its operational flexibility since it is essential that the capacity available exceeds the demand, despite the high costs of creating that excess capacity.

References:

• Unsafe water kills more people than war, Ban says on World Day". UN News. 22 March 2010. Retrieved 10 May 2018
• Raymond Desjardins- Livre: Le traitement des eaux- 2éme edition- Ecole Polytechnique de Montréal- 1997- ISBN 2-553-00643-8
• Drinking Water Treatment- EDX- Delft University of Technology.
• Book- Drinking Water: Principles and Practices- by Hans J C Van Dijk (Author), Jasper Q J C Verberk (Author), Peter J De Moel.