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| Services |
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| 1. Greenfield or new water treatment plants based on Tube Settler technology / clarifiers read more... |
| 2. Single or multimedia gravity filter beds. read more... |
| 3. Complete water treatment systems and Water supply schemes read more... |
| 4. Augmentation or retrofit of existing plants for capacity or quality up-gradation read more... |
5. Mass application of small capacity standardized plants
read more... |
| 6. Sewage Treatment Plant. |
| 7. Project Management Consultancy. (PMC).. |
| 8. Civil, Structural, Electrical & Automation Engineering design & drawings. |
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| Research Paper & Presentation |
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| Rajendranagar Municipality , Andhra Pradesh, INDIA |
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| Augmentation of existing water treatment plants |
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| Introduction : |
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For more than four decades, the drinking water supply to this municipality was made through a
Water Treatment Plant built in the year 1960 (by Geo-Miller) with original capacity at 3.15 mld
(million liters per day). The plant constituted a Receiving Chamber, Flow measuring weir, single
Clariflocculator and three Rapid sand gravity filter beds. The ancillary structures included a double
storied chemical house, wash-water tank located above the house, a sump and pump-house. The
source of raw water is a shallow lake (man made reservoir called Himayatsagar), polluted with
organic matter and laden with algae. The raw water supply from this lake to the plant is by gravity.
The Municipal council, based on the population census and consumption pattern (140 liter per
capita per day), had projected a demand of 8.15 mld by the end of year 2005. As witnessed in
April 2002 itself, the plant was operated at 4.50 mld under overloaded condition. As a result the
treated water quality suffered and filtration cycles had shortened.
Lot of effort was put into the consideration of various alternatives for additional treated water
supply (5 mld) to the town, before the Municipal Council diligently decided to upgrade the
capacity of existing water treatment plant itself from 3.15 mld to 8.15 mld. The plant was 6 km
from the bustling city of Hyderabad and there was no space for construction in the old plant
premises, while logistics did not allow construction elsewhere. By upgrading the existing plant, all
the lacunas and system inefficiencies built over the past four decades would be addressed. Most
importantly, the cost of augmentation would be lower than the cost for a new plant by atleast
40%. The project would be funded by the Municipality�s internal revenue resources and external
borrowings, thus to look at all possible options to save money, was natural. It was thus decided
to go unconventional and upgrade the existing plant by mainly retrofitting the existing units with
advanced unit processes wherever possible and to construct new structures in case absolutely
essential.
The major modifications to the plant included conversion of Clariflocculator into Tube Settler (with
higher rise rate) so as to generate additional clarified water from the same unit. This is done by
placing the modules in a annular ring adjacent to the outer wall of Clariflocculator with a surface
loading rate of 5000 lph/sqm. The cantilevered trusses projected from the inside of outer wall
supported the new carbon steel partition wall and the modules. The concentric circular wall of
flocculation zone was dismantled. Thus the portion inside the new partition wall was available
as a flocculation zone with 40 min detention time (DT) for enhanced flow. Other Modifications
to flocculator included enhancing the �G� value by increasing the paddle area. Radial collection
troughs were provided over the tube clarification zone, discharging the water to existing peripheral
collection launder. Vertical arms of scrapper bridge were relocated so as not to interfere with the
tube zone.
The Clariflocculator is provided with a buried underground feed pipe. Enhanced flow generated
the additional headloss through this pipe. The elevations of units on the upstream side were
raised appropriately to accommodate the additional head. The existing receiving chamber was
provided with baffles to create a flash-mixing chamber with a 30 second DT. A rectangular weir
was provided on the down-stream of chamber for measuring the raw water flow.
The existing three rapid sand gravity filters were constructed in the stone masonry. Their
conversion to high-rate dual media filters demanded exhaustive modifications. It was decided to
only revamp the filters physically and to restore their capacity to 4.0 mld and to construct two new
filter beds to treat rest 4.15 mld flow. The revamping of existing beds included replacement of
worn out media, replacement of damaged laterals and nozzles and overhauling of control valves.
Two new rapid sand filters, each having a capacity of 2.0 mld with a rate of filtration 6000 lph/sqm
were constructed and integrated in the available space. The filters were designed on the principle
of �Constant rate filtration with influent splitting weirs�, which eliminated the maintenance prone
rate of flow controllers. The filter beds were sized in such a way that existing wash-water tank and
air blowers were integrated with the new beds. The hydraulics demanded operating levels of new
and old filter beds to be same. Additional pipeline of 4.15 mld capacity was laid from modified
Clariflocculator to the new beds and from new beds to the Filtered water sump. The hydraulics of
new beds ensured that existing wash-water and sludge disposal arrangement could be utilized for
the purpose.
The actual execution was started in February 2003 and plant was commissioned in September
2003. The plant modifications took place without disturbing the normal water supply (3.15 MLD)
to the town. The treated water quality at the augmented flow has enhanced significantly. The
planned schedule got stretched by two months due to drought situation in the state. During the
drought, the raw water quality deteriorated to a high extent. As a result the Clariflocculator could
not be bypassed for the modifications. The project was completed at the cost of INR 4.0 million
( USD 0.080 million) which was 60% of the cost of a new plant had it been constructed. Indirect
benefits included saving in land cost. Electrical consumption only increased marginally. The entire
existing machinery got overhauled. The existing trained staff is happily operating the old plant with
renewed vigor.
 Layout Plan of Augmented Plant
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| Acknowledgements : |
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| Authors will like to thank all organizations (govt., private and semi-govt.) who have participated in
these case studies. Thanks are also due to their managers, engineers, chemists and operators who
have given invaluable help to compile this data. |
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