Tutorial 5

This tutorial is designed to impart basic concepts of plant siting and hydraulics of water treatment systems.

A map of IIT Kanpur campus is given in Figure 1 and Figure 2. Based on these maps, it was decided that the water treatment plant would be sited in the empty land available in the western end of the campus. A contour map of the IIT Kanpur campus is shown in Figure 3.

The plant should be designed such that water through the plant flows without pumping. This may be impossible in a place with flat terrain, as is the IIT Kanpur campus, unless the ground elevations at the plant site are changed significantly through earthwork. Luckily, as per our design, significant amount of soil is available for this purpose from the excavation of the raw water tanks, as described in tutorial 2. A part of this soil will be used to change the ground elevation at the water treatment plant site.

For determining the hydraulic grade line, or the water surface level at various parts of the treatment plant, the head-loss through various treatment units must be known (see schematic in Figure 4). Following information regarding water surface levels are given:

· pre-chlorination tank: Difference in elevation of inlet and outlet water surface

level to be calculated using slope of the channel,

as determined by Manning’s equation.

· rapid max tanks: 0.3 m difference in water level between inlet and outlet

· flocculation tank: 0.6 m difference in water level between inlet and outlet

· secondary clarifier: 0.6 m difference in water level between inlet and outlet

· Rapid sand filters: 4.0 m difference in water level between inlet and outlet

Water will be conveyed from one process unit to another through open channels of 1:100 slope.

Water from the rapid sand filters will be conveyed to a covered clear-water sump with a storage capacity of 6 hours.

· Covered underground

clearwater sump: 1.0 m difference in water level between inlet and outlet

Water from the clear-water sump will be pumped to four overhead tanks located in various parts of the campus. Water from the overhead tanks will be fed to the distribution system by gravity.

Figure 4. Water Surface Level Schematic of the Treatment Plant

Post-chlorination will be performed by addition of chlorine through jet mixers in the four pipes at the exit from the clear-water sump. Retention of water in overhead tanks must provide sufficient contact time for post-chlorination to be effective.

· Design the layout of the water treatment plant, based on the plant sizing done in tutorials 2, 3 and 4.

· Clearly mention the ground level and corresponding water level at various points of the treatment plant.

· Mention the quantity and degree of earthwork required for changing the ground level at the plant location.

· Design the required pumps and other water conveyance units such as open channels and pipes.

· Design the overhead water tanks such that the tank near the MT section supplies 40 percent of the water, while the other tanks supply 20 percent each.

· Design the pipes and pumps required to supply water from the treatment plant to these overhead tanks.