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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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Case Studies
Mabayun (Subic Bay), Philippines |
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| Introduction : |
In 2007, Subic Water was owner and operator of the drinking water supply schemes for Subic Bay and surrounding areas. There were raw water sources for the water treatment plant, Old Dam and New Dam. Old Dam was supplying water by gravity to treatment plant complex. The raw water from New Dam was pumped to treatment plant complex.
The blended water had mixed characteristics like high grit load, high algal load and high turbidity peaking up to 2000 NTU. The treatment plant complex consisted of old plant ( 9 mld capacity) with a Carbon steel clarifier , carbon steel gravity filters and diesel pumps for pumping the treated water. This facility was constructed way back when there was a U.S. Naval base. The new plant (19 mld capacity) consisted of a concrete Clariflocculator and concrete duel media filter beds. The Inlet works, Chemical House and Pure Water Sump were the common facilities. The rapid mix arrangement was absent from the clarifier. Out of the total design capacity of 28 mld, the plant was barely able to produce 20-22 mld treated water as the old plant had become dilapidated.
It was proposed by the Subic Water Authority to reinstate the existing plant to enhance the capacity as much as possible. The treatment plant complex didn�t have much space for construction of a new plant. After detailed study it was decided to decommission the old carbon steel filters they were corroded to an extent. Since the old clarifier was structurally sound it was proposed to be retrofitted with flocculation-tube settler to produce 16 mld water. A new common Inlet works of concrete construction ( Capacity: 16 + 19 = 35 mld). The Inlet Works consisted of a Receiving Chamber, Cascade steps, Mixing weir, a grit separating chamber. A splitter flow arrangement was to create two separate streams of 16mld and 19 mld each. The additional 16 mld clarified water was to be further polished off in new duel media filter beds. A lot of interconnecting creative piping was proposed to be done during the retrofit. All the activities were planned, sequenced, engineered to have minimum shut down period of operating system.
The plant was commissioned in 2009. The Inlet Works and retrofit of old clarifier was done within three months and integrated with the existing system. During the trial run PolyAluminium Chloride and a cataionic polymers were dosed at the mixing weir. Prechlorination as well as post-chlorination were practiced to main the residual chlorine level of 2 mg/lit. The clarifier operation with tube settler was extremely stable under varying turbidity. It consistently produced clarified water turbidity of less than 2 NTU.
Subic Water not only augmented their plant capacity at a minimum cost, refurbished the old equipment, saved the precious land and improved the drinking water quality simultaneously.
Common Inlet Works of existing plant 
Old Clarifier, Capacity 9.0 mld
New Inlet Works for 35 mld facility 
Mixing weir and dosing pipes
Central flocculation and outer settling zone 
Tube Clarification zone of modified clarifier
Photographs of Subic Bay Plant
Courtesy: Chemitreat, Subic Water Authority, Philippines
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