On December 2017, I got an opportunity to visit drinking water treatment plant in Tirtawening, Bandung, which is near my college. It was a very amazing experience, because this is my first experience visiting water treatment plant. And also, experience like this is very rare after I entered working environment.
This site visit is actually a part of water treatment plant training. I will share you about this training in different post.
Drinking water treatment facility in Tirtawening is actually the biggest one in Indonesia. It processed 2000 liter/second water, from two trains (rate of each trains is 1000 liter/second). 1900 liter/second water is sent to customers and 100 liter/second water is own used.
Sources of water are from ground water (from south of Bandung, about 32 km distance, and transported by gravity, and from north Bandung), surface water, and water springs.
Figure below shows general production process of drinking water in Tirtawening.
The first process in drinking water treatment plant in Tirtawening is garbage removal. After the raw water collected, it brought so many garbage with it. The garbage are leaves, plastics, etc. The garbage must be removed from the water. The garbage removal is conducted semi automatically. Sometimes, operators must remove the garbage by hands.
After that, PAC based coagulant is added to the raw water. PAC stands for poly aluminum chloride. Mixing of water with coagulated is conducted naturally by hydraulic mechanism, which is by mixing of water from north source and south source.
Addition of PAC coagulant will neutralize the negative charges in solid particles. Then the particles will stick together forming a larger particles which can be easily removed.
The next step is flocculation. In flocculation, the particles that have a neutral charge will be slowly mixed, so that the small particles will form larger particles called flocs. Mixing is done slowly. If the mixing is too fast, the flocs will break apart, thus the particles are difficult to be removed by sedimentation and filtration.
The next step is sedimentation. Sedimentation itself is conducted for 30 minutes. Sedimentation process is conducted in sedimentation basin and in tube settler.
In sedimentation, large particles are settled, then clarified water is produced, where most particles are removed.
Flocs settled at the bottom of sedimentation basin are removed every month.
The next step is filtration. Filtration is conducted in many large concrete ponds. The ponds contains sand, which will filter the water, gravel, which keeps the sand from getting out, and underdrain, where the filtered water exits.
After filtration pond is operated for some time, the sand becomes clogged with particles, so that it must be backwashed. In backwash, filtered water is pumped back through the filter to flush out the particles.
After filtration, the filtered water is disinfected by using chlorine gas. The function of disinfection is to kill pathogens remains in the water before distribution.
That’s all I want to share. I hope you enjoy this post and my little journey!