TUTORIAL-I

The schematic of a typical water supply scheme is shown below. Raw water is collected from a source, which is a river in this case, through an intake structure, and pumped to the treatment plant. The treated water is collected in a sump well and then pumped to an elevated distribution reservoir for distribution by gravity to the distribution system. The objective of successive tutorial classes will be to design various components of this system.

Water

From River

Water to

To Distribution System

For the purpose of this tutorial, we will assume that the community in question is the IIT Kanpur campus. Water is to be supplied to the campus by pumping raw water from the Ganga River. The intake structure for this purpose will located a little distance upstream of Bithoor.

Before designing the system shown above, information is required regarding the capacities of various components of the system. This information is obtained through the estimation of the water demand of the community. Following tasks need to be completed for obtaining information as described above:

Task #1: Population Estimation for year 2000 and year 2020

First task is to estimate the population of IIT Kanpur Campus in year 2000 and the expected population in year 2020, given the following information:

Table 1. Types and Numbers of Residential Units of Various Types and Number of Residents in Each Unit in Year 2000

Type of Residence	Number	Avg. No. of Residents per Unit
Type 1	192	6
Type 2	220	5
Type III	192	4
Type IV	200	4
Type V	40	4
Hostel	6	500
Servant’s Quarters	300	5

In addition, remember that IIT Kanpur Campus is a restricted access community, where population growth is controlled through policies adapted by the Institute authorities. Current Institute policies envisage an increase in the student population of the Institute from 2100 in 1994 to 4200 by year 2004. No further increase in student population is planned after this doubling of population. In spite of student population doubling, neither the faculty, nor the staff strength of the Institute is expected in increase in the next twenty years. Hence, though new hostels will have to be built, construction of additional residential quarters for faculty and staff are not envisaged in the next twenty years.

Task #2: Estimate the water Demand in Year 2000 and Year 2020

Average domestic water demand is 180 lpcd (liters/per capita/day) in year 2000. This is expected to increase to 235 lpcd in 2020. In addition, temporary population, i.e., people who do not live on campus but visit the Institute daily for various reasons, is expected to be around 3000. Water demand for this population is expected to be 40 lpcd in year 2000 and 60 lpcd in year 2020. Water demand of the commercial establishments, i.e., academic area, health centre, restaurants, community centres, shopping centres, etc., is expected to be about 50 % of the total domestic water demand. Fire demand is given by the formula, Q = 100 , where P is the population in thousands and Q is the water demand in kiloliters. Water demand for horticultural purposes 0.5 cm-acre/d, with the total area requiring this water being 100 acres.

Ø Estimate the average daily demand in year 2000 and 2020 (which includes residential, commercial and horticultural demand) based on the above information. Also calculate the fire demand in years 2000 and 2020.

Ø The water demand in summer months is expected to be more than the value calculated. Assume maximum daily demand to be 1.8 times the average demand.

Ø In addition to daily variations, hourly variations in water demand must also be taken into account. Assume maximum hourly demand of the maximum day to be 2.7 times the average daily demand.

The critical water demand is obtained by comparing the sum of maximum daily demand and fire demand (A) with the maximum hourly demand of the maximum day (B). The larger of these two values will be used to design the distribution system to serve the community. The smaller of the two values will be used to design the size of treatment plant and the pipe for conveying raw water to the treatment plant. The clear water tank, i.e., that tank(s) constructed to hold treated water before distribution should be large enough to store the difference between the above two values (A and B) for twelve hours. Based on the above information, determine the capacities of various components of a water supply, treatment and distribution system.