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

P H adjustment, lime solution is proposed to be used. For preparation of lime
solution, 2 lime mills are proposed to be installed. Lime dosage shall gravitate to
the raw water inlet stilling chamber, an area of maximum turbulence, for proper
mixing of the solution. The chemical house shall be of 2 storeyed building of size
10mx28m to fit the land availability at the site. The 2 nos. Alum mills and 2 nos.
Lime mills of the existing water treatment plant are also proposed to be re-allocated
at the ground floor of this building in addition to the alum mills and lime mills for
the new treatment plant. The ground floor shall also be provided with space for
storage of chemicals viz. Alum and lime including separate room for storage of
chlorine gas cylinder, absorption tower, chlorine gas panel for water disinfection.
The 1 st floor of the building shall housed laboratory etc. where a full fledged
dedicated and well equipped laboratory is also proposed to be set up.
Rapid mixing :
For rapid mixing of raw water with the coagulant, flash mixer is proposed to be
installed. After measuring channel, raw water alongwith coagulant shall enter a
flash mixing well where the coagulant added shall be rapidly and intimately mixed
with raw water by the agitator assembly.
Clari-flocculator :
Primary treatment : Under this package, it is proposed to construct clari-flocculator
identical in size and shape and having same level of construction as that of the
clari-flocculator of existing 34.05 MLD water treatment plant. The clarified/settled
water of both the clarifier shall be shared by both the filtration plant i.e. existing
34.05 MLD and proposed 8 MLD by interconnecting the clarified/settled water
channel of both the clari-flocculator. Dosed water from flash mixer shall flow
through a hume pipe of 600mm bore to the central shaft of the respective clarifier
and enter the flocculating zone at the top of the shaft through 4 openings in the
shaft wall, each opening 600mm high and 150mm wide. In the flocculating zone,
which shall be 15m dia. with an effective flocculating depth of 4.5 m, the water
while flowing downwards shall be stirred by 3 sets of flocculator paddles. It shall
then passes below the flocculator wall to the settling zone of the clarifier flowing
radially outwards and upwards to the outlet launder. The clarifier shall have a
diameter of 37m and side water depth of 4m. The detention time of flocculator shall
be 30 minutes and that of clarifier 2.8Hrs.
DTS : Detailed Tender Specification. Page 240