M.A.G.D. Wimukthi
GROUP   B
FMS/R/ 2974
POST   03

Today is first day of 3^rd week in our clerkship programe. Another new experience to us at Raddoluwa water treatment and. sewerage plant

We arrived there at around 8.30 am. 

This water treatment plant commenced in 1987.

.It is belongs to National water supply and drainage board. Plant now contain 2 treatment units. 

older one use to water supply to houses in the scheme and new one use supply the water to houses in the village and Katunayaka industrial zone.

Dandugan oya is the water resource for the plant. From there water pumps to well in the plant through large pipes. Then aeration process go on. In this step water mix with O_{2 .} Cascade method is use in old plant and disc method use in plant. Ions and other harmful particles. In the water are broken down during this process by oxidized water.

After the aeration AL₂(SO₄)₃ and Ca(OH)₂ is added. Ca(OH)₂ increase the pH of media and promote the formation of mud floccules by Al₂(SO₄)_3.

Then water sends to sedimentation tanks. These tanks are 15 feet in depth. Water slowly flows through parallel steel plates in zig-zag way. During the flow mud floccules hit the plates. floccules sink and collect at bottom of tank. Water flows in to the filters

Mud free water come to the filtering process. 

Normally filters composed of ,

                  Superficial (sand) layer

                 Middle (granite chip) layer

                Deep (concrete slabs with nozzles) layer.

Small particles retained in the filters. When filters are obstruct by these particles back wash the filters with air and cleaned water.

Cleaned water ten came to storage tanks. 2tanks .One is on the ground and other one is in the ground.  Chlorination is performed   at storage tank. This is usually done by bubbling of chlorine gas.

Finally distribute to their customers. Mud floccules and back washed water return to lower level of Dandugan oya.

That is the process of water treatment plant. All of these information gave to us by Officer in the water board.

So this is the end of my post 03. We will meet again with post 04.