Ambatale Treatment Plant Ambatale Water Treatment Complex is one of the major supply drinking water to Greater Colombo Colombo area . There There are two plants operated operated at Ambatala, old treatment plant commissioned in !"" # capacity of nearly $$%,&'' m$(day and new plant commissioned in !!) # capacity is *',''' m $(day. The +eld isit was focus on old treatment treatment plant.
-rom the elani /ier, Ambatale Water Treatment 0lant gets its water supply. Ambatale Treatment 0lant , 0ump from the elani /ier by the two 1 pump houses on the left bank of the elani /ier. These pumps work 1) hours. Therefore Therefore a large sum of money has to be spent spent on electricity. electricity. T he water that is found in the riers riers # reseroirs reseroirs are usually not not suitable for drinking. The water in the elani elani /ier is polluted by the actiities of man # animals. The e2uents of the industries situated along the rier, domestic wastes,storm water, and sewage3all enter the rier through a system of drains # waterways. waterways. 4ence the rier water water is not suitable for for drinking. The steps of water treatment process process are 5creening # per sedimentation, aeration, coagulation # 6occulation, sedimentation, +ltration, disinfection and stabili7ation. -inally, treated water is stored stored in underground reseroir reseroir and pumped into the transmission line.
Screening & Pre – Sedimentation 8echanical screening is done to trap and remoe 6oating matters # other large particles which can clog or damage plant structures. 0re3sedimentation is done to remoe remoe silt, sand and other particles.
Aeration Aera Aerati tion on proc proces ess s addin adding g air air 9oxy 9oxyge gen: n: into into wate waterr. ;t manag manage e to remo emoe e oxidi7e oxidi7es s impurities impurities such as iron and manganese, manganese, troubles troublesome ome gasses gasses like 415 # <4$ and reduces certain types of tastes and odors. Cascade type aerator is used in plant.
Coagulation & Flocculation Flocculation
The chemicals use for Coagulation # -locculation are =ime and Alum. >oth raw water ?uality and treated water ?ualities are checked by following parameters as Conductiity, turbidity, p4 and residual chlorine. @ar test, marble test, chlorine demand test # residual alum test are doing to +nd out the optimum dosage of chemicals. When chemicals are added to water, it reacts with soil # clay particles, microorganisms #other substances. This is called Coagulation. These particles associate with similar particles to form big 6ocs. The process is called -locculation. The 6ocks when it is heay sink to the bottom. The result is clear water at the top. At the 0lant, these dosages are added proportionately to water. There is a laboratory to check the water ?uality there both raw water ?uality and treated water ?ualities are checked by following parameters as Conductiity, turbidity, p4 and residual chlorine. @ar test, marble test, chlorine demand test # residual alum test are doing to +nd out the optimum dosage of chemicals. $ chemicals used for Ambatala water treatment plant as followsB •
-or 6occulation
B Aluminium sulphate
•
-or p4 adjustment or correction
•
-or pre treatment and disinfection B chlorine 9Gas or li?uid:
B Calcium hydroxide 9=ime:
=ime solution 90re lime: is added for 04 adjustment of the raw water in the existing chamber to get optimum range of coagulation. Alum solution is added in the new mixing chamber aboe the inlet weir for better mixing # coagulation.The lime slurry 6ows into the distribution chamber by graity from tank.
Sedimentation There are four types of settling tanks used Centi6oc, pretreator, pulsator and pulsatube
Tank Type
Centi6o
5edimentation
Water
Tank Capaci ty 6ows %%!
utput capaci ty
Detentio n time
5ludge remoal
$.&8
1
1.* hrs
Accumulated
c
ertically upward m$ through the sludge blanket and 6ocs are stick on it and clari+ed water goes up.
GD
0retrea tor
Water 6ows !)"1 ertically through m$ the sludge blanket and 6ocs are stick on it and clari+ed water goes up,
$.&8 GD
1
$.% hrs
Accumulated excess sludge is released by an automatic mechanical de3sludging system
$.&8 GD
1.$" hrs
excess sludge is released by an automatic mechanical de3sludging system.
5ludge recirculation is allowed in order to get optimum 6occulation 0ulsato r
When the water "'1 with 6ocs going m$ downwards through the blanket the 6oc rest on it.
0ulsatube is 6at bottom sludge blanket clari+ers, 6oc settle on the surface of tube.
Filtration
' 8DG
5ludge is remoed using pressure gun
There are 1' +lters existing at the plant, where 1 sand media +lters # * A?ua7ur E +lter .The sand +lter hae capacity of "*'' m$ per day. Fectie si7e of sand media is '.!mm, uniformity co3eHcient .& and depth of sand media is '.!m. As water go by the +lter bed, the suspended particles contact and adsorbs onto the surface of the indiidual +lter grains or onto preiously deposited material. Water leel is regulated by 6oat control. The deposits in +lter beds are diluted by the back wash process. There is an automatic sensor system for back wash processes. -ilter backwash is taken place once it reaches the predetermined water leel or when water 6ow stops, that is the time for backwash the +lter tank. -or backwash -irst air scour is done then water is sent upwards through the +lter media. 5and in +lter bed is re+lled once in $ to ) months time period.
Disinfection Then post chlorination is done, in order to preent the spread of waterborne diseases, by proiding protectie residual within the distribution system to guard against inadertent bacterial contamination. 8ostly li?uid form Cl1 is taped and apori7ed to Cl1 gas. Then that Cl1 gas mix with water and feed it to water on the line connecting the clear water tank.
Post lime 0ost =ime addition is done for p4 correction in order to aoid corrosion or CaC$ deposition. =ime is added after the chlorination process on the same line connecting the clear water tank. ;t was obsered that post chlorine and lime is added at the same location.
Issues and Suggestions to be incorporated in augmentation The Ambatala water treatment plant needs renoation and augmentations in some areas. The following actiites can be address to proide the ?uality drinking water and safe the enironment of surrounding area including alani /ier.
Ambatala water treatment plant generated around "''' m $(day wastewater and it is discharged to the elani /ier. The wastewater can be treated before release to the rier or the treated wastewater can be used for gardening purpose. 1 At present this plant does not hae sludge treatment facility. At the moment the sludge also discharged to elani /ier. ;t could be treated in proper manner and disposed in another place $ The back wash system automated with pneumatically energi7ed ales is not reliable. The system and the backwash se?uence could to be renoated. ) 5ome +lter beds are not working properly stagnating without +ltering. These will contribute to deterioration of +nal water ?uality. The plant could be monitor and maintain properly in order to proide ?uality portable water. & The pulsator can be conerted to pulsatube to further improe clari+ed water ?uality and the capacity. " 0ost Chlorination is to be improed with the contact tank 91' minutes contact: before pumping to the distribution line to ensure eectie disinfection.
