PACKAGE : I Bid Document VOLUME : II - Public Health Engineering

Chapter 21
Water Treatment Works.
21.1 Existing water treatment plant.
2 Nos. water treatment plant were constructed under Phase I & II of the project for
providing treatment of raw water lifted from the reservoir through 2 stage pumping
system. The first WTP of capacity 34.05 MLD were completed and commissioned
in 1986 and the 2 nd WTP of capacity 17.25 MLD were commissioned only few
years back.
21.2 The constructional features of different units of the existing
34.05 MLD water treatment plant.
Inlet, stilling chamber & measuring channel:
Raw water is received in the stilling chamber 2mx2mx2m whereafter it flows
through a Parshall Plume in the raw water channel for measurement of flow rate.
The raw water channel is 2m wide and the Parshall Flume have a throat width of
1.22m.
Chemical treatment:
Alum in solution is used as coagulant. For preparation of solution, two tank are
provided, each 3mx3mx1.75m depth. Each tank hold sufficient solution of 5%
strength to provide a dosage for eight hours for a flow of 34.05 MLD. Solution
gravitate to a constant head dosing tank placed over the raw water channel and
solution flow directly from the dosing tank into raw water through a taper needle
valve at a preset dosage which will adjust itself automatically to any change in flow
rate o£ raw water. Lime suspension is prepared in two lime mills, each capable of
providing dosage of lime solution for eight hours for a flow of 34.05 MLD. The
dose, diluted with about five times its own volume, gravitate to the raw water
stilling chamber.
Flash mixer :
After measurement, raw water enter a flash mixing well of 3.20m dia x 1.50m mix
depth where the coagulant added is rapidly and intimately mixed.
DTS : Detailed Tender Specification. Page 231