A country town C has a present population of 6000 people and is growing at the rate of 3% per year. The town is currently supplied with water by gravity through 6 km long 300 mm diameter pipeline, continuously over 24 hours/day from a small and shallow reservoir A to a partly excavated 9 ML service basin B as shown in Fig. 2a. A 2 km long 400 mm diameter main then feeds from the service basin into the town reticulation system. The water supply demand on the peak day is assumed to be as shown in Fig. 2b. Because of the expected population increase by year 2035, a proposal has been forwarded to augment water supply by pumping from the near by river at D to the service basin B during the peak demand period.
Streams feeding the reservoir and the nearby river flow through farm land pick up a range of contaminants from overland runoff. Periodic problems have occurred in the service reservoir water with respect to microbiological contaminants, algal blooms with associated taste and odour, colour, iron and manganese. Accordingly it has been decided to construct a water treatment plant for the town supply. Assume C = 100 and use the nomograph for Hazen - Williams formula in all pipe flow calculations.
a) For the present arrangement, check whether the capacities of pipeline AB and BC and the service basin B are adequate.
b) Calculate the total annual demand which will be imposed on the water supply system at the end of the design period.
c) Calculate the required pipe size for the rising main DB, assuming that pumping would occur at a uniform rate between 8 am and midnight on the day of maximum demand at the end of the design period.
