actual water treatment process

8/7/2019 Actual Water Treatment Process

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L OCAL WATERTREATMENT

PLANTS


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Residents of Muntinlupa City now enjoy potablewater from Laguna Lake, the country s biggestfresh-water body, thanks to a treatment plantbeing built by Maynilad Water Services Inc.

The facility uses dissolved-air flotation,microfiltration, reverse osmosis and chlorinationto produce water from the lake that Pall Corp.claims exceeds the Philippine NationalDrinking Water Standards. Despite theseprocesses, water from the plant has a moldyodor and taste, which consumers can removewith the use of a carbon filter.


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P ROCESSES I NVOLVED

1 . Lake intakeAn intake structure 400 meters from theshoreline draws water from Laguna Lake.The water passes through twin (2-m x 1 .75-m)ducts.

2. Forebay

Water is fed into the forebay by gravity. Thewater is continually replenished in theimpounding area depending on demand.


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3 . AeratorA twister machine aerates the raw water in

the forebay.

4. Vertical pumpsThree vertical turbines ( 13 2 kW, 880 rpm)pump water from the forebay into dissolved-air-flotation (DAF) tanks.

5. CoagulantAluminum chlorohydrate, a coagulant, fromthese tanks is added before raw water goesinto the DAF tanks.


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6 . MixersIn the first stage of the DAF process, mixers infour tanks slowly blend the water with thecoagulant, which binds to blue-green algae,silt, dust, and metals like iron and manganese

to form flocs (loosely clumped masses of fineparticles).

7. Air concentrator

In the second stage of DAF, air from this tank isinjected into two chambers holding themixture of water and coagulant, producingsmall bubbles that make the flocs float.


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8. SkimmersSkimmers remove from the surface the flocsthat form into sludge. Scrapers remove solidsthat settle on the bottom. The sludge goes intoa trough and into a sludge tank (lagoon at this

time) where it is decanted to remove water.Solids are left for hauling.

9. Feed pumps

Six turbines (2 1 5 horsepower at 1 ,790 rpm)pump water into strainers and intomicrofiltration and reverse-osmosis trains, andfinally into the reservoir.


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1 0. StrainersFive stainless strainers remove remaining solids(up to 3 00 microns) from the water, clear by now,at a maximum flow of 1 ,200 cubic meters per hour.A micron is a thousandth of a millimeter.

11 . Microfiltration systemPolyvinylidene-fluoride filters screen outparticles up to 0. 1 micron, removing mostviruses and bacteria. This process uses 1 4 rackswith 6 8 modules each.


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1 2. Reverse-osmosis (RO) system

Salt is removed from the water using sixidentical RO trains (5. 6 mld of permeate flowper train) when salinity in the lake reaches 500parts per million. Last June and July, for

instance, salt water from Manila Bay intrudedinto the lake through the Pasig River. The brineresulting from reverse osmosis is expelled intothe lake.

13 . Permeate tank. A 3 0 cubic-meter tankcollects water from RO trains.


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1 4. ChlorineChlorine is added to kill pathogens.While the chlorine equipment has yet to be installed,

granules of calcium hypochlorite (which have a 70-percentchlorine content) are used.

1 5. ReservoirThe reservoir can store 1 4 million liters a day (mld). It hastwo chambers Chamber 1 can hold 6 .6 mld and Chamber2, 7.4 mld.

16 . Booster pumps

Three 200-kW booster pumps for Ayala Alabang and three480-kW booster pumps for other communities distributepotable water to May-nilad customers, producing 88 psi(pounds per square inch) of pressure that allows water to besent to multi-story houses and tall buildings. The pressure

drops to 20 psi when water reaches end users.

actual water treatment process

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