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| 1. Greenfield or new water treatment plants based on Tube Settler technology / clarifiers read more... |
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| 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
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Case Studies
Purvakarta, West Java, Indonesia |
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| Introduction : |
One of the World�s largest viscose fiber manufacturers, PT South Pacific Viscose has its largest unit in Purvakarta. In 2012 their water treatment plant complex consisted of several plants added to the facility according to their expansion water demand.
(A) Two clariflocculators and gravity filters of 2000 cum/hr capacity (1982).
(B) Lamella clarifier and Dynasand filters of capacity 500 cum/hr.(1994).
(C) Ultra-highrate solids contact clarifiers with Dynasand filters of capacity 500 cum/hr.
When their fifth manufacturing unit was planned, it required a dedicate Fire Water Storage Tank of 3000 cum for which there was no space available at site. Finally they decided to take one existing clariflocculator of 1000 cum/hr capacity and to convert it in to Fire Water Storage tank (FWST). The shortfall in the treated water supply was to be made-up by converting the other clariflocculator to 2000 cum/hr capacity by retrofitting it with tube settlers.
The raw water Intake Well is located just on the downstream of confluence of two rivers. One river is fairly polluted and turbid while the other river has clear water. The naturally blended water is pumped to the treatment plant complex. The raw water rising main had capacity to feed all the existing plants. The clariflocculators were preceded by a Cascade Aerator, flow measuring notch, a mechanical flash mixer and split flow box. All the three units were already designed for flow rate of 2000 cum/hr. The isolation gate of split flow weir which was to feed the water to FWST was closed.
The existing DORR clariflocculator was designed for flocculator DT of 40 min and clarifier surface loading 1.5 cum/sqm/hr. By doubling the flow to 2000 cum/hr the flocculator DT was reduced to 20 min. To compensate the �Gt� value the paddle area of stator-rotor mechanism was increased. Tube settlers with square tubes with a surface loading rate 6 cum/sqm/hr were placed in a form of annular ring in the clarification zone. The scrapper arm of the rotating bridge was modified to sweep the sludge below tube modules towards central pocket. Additional pipe, opposite to existing channel (conveying the water to filter) was laid up to filter beds to restore the capacity of collection launder of clarifier.
The buried inlet pipe (diam: 600mm) feeding water to clariflocculator would have generated additional headloss on the upstream side (flash mixer) due to doubling of flow. Since the flash mixer freeboard was inadequate to accommodate the increase depth, the height of the walls of flash mixer was suitably raised. Two no of polyelectrolyte dosing tanks and pumps were provided in addition to the alum dosing system. The entire retrofit work was done in six months. The augmented and refurbished plant was commissioned in 2013. The trial runs were operated at 2500 cum/hr capacity. In high as well as low turbidity the plant operation was stable. For inlet raw water turbidity of 20 NTU, PAC DOSE of 8 mg/lit and PE dose of 0.4 mg/lit were administered. The clarified water turbidity was found to be consistently less than 2 NTU.
Cascade Aerator and Inlet Works 
Erection of clarification partition wall
Clarifier retrofitted with tube settlers 
New Chemical House and store
Photographs of PT South Pacific Viscose Plant
Courtesy: M/s Thermax Ltd, Pune, Maharashtra
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