< MODULE 2 >
As the city produced clean and safe drinking water, and supply to the ten million citizens, the city has to take much care about the water quality management. The city monitors water quality parameters of 164 items periodically from the source to the tap.
We had problems with algae in this summer. As you can see the color shows the concentration of algae, and as you can see the first one is the algae concentration in June, and the other one is in July.
And as we can see as temperature went up the concentration of algae increased and it looks like the algae concentration moves up to the upstream. The problem with algae is the chemicals called Geosmin and 2-MIB.
Those chemicals cause taste and odor problems in drinking water. It tastes earthy or mushroom-like taste and it has odor, so citizens can have problems with the drinking water with Geosmin and 2-MIB.
And we the city made an alerting system for the algae, algae alerting system, and also the city have taste and odor alerting system. So the operators for the treatment plants, and supply system, can be prepared according to the stage of alarm.
The monitoring system that we mentioned before is done by hand, which means the staffs go out to sample water and take the water sample to the lab and analyze it by hand. The city has another monitoring system for water quality parameters.
It’s real-time online system. We call this system Seoul Water Now System. This graph shows the number of monitoring water quality parameters and the cleanness of the drinking water.
As the number of monitoring parameters increased, the turbidity, which is the dirtiness of the water, is going down. When we started to monitor the water quality parameters in 1989, the turbidity of the drinking water, treated water is about 0.5 NTU.
It decreased to 0.05 NTU in 2010, which means the drinking water of Seoul became 10 times cleaner in 2000 compared with the 1990s.
This is the system of Water Now System. We have two hundred monitoring sites all over the Seoul from the source to the tab , and as we can see we have six monitoring sites in intake station and another six for water treatment plants, and 99 sites for reservoir, and 77 for tap.
The city has plan to increase the 200 more monitoring site in the future. The water quality parameters monitored in each site is different because for the source water we don’t need to check the residual chlorine, but at the tap we measure the 5 major water quality parameters including turbidity, pH, residual chlorine, electric conductivity, and water temperature.
With these 5 water quality parameters we can decide if the safety of water is a problem or not. Seoul has 8 drinking water districts. As you can see the colors show the each district, and we have 200 monitoring site all over the Seoul, from the source to the tap.
The data and information collected from the 200 sites is opened to the public via internet. So the citizens can check the water quality of their community anytime, anywhere through the internet like this.
And the data and information is also opened to the public through smartphone app, and also we use the electronic board to show the data and information to the citizens in real time.
The next topic is advanced water treatment system. We have treatment process with conventional process and advanced process.
As we discussed before, the chemicals related with the algae, which are 2-MIB and Geosmin, these kinds of chemicals is hard to be treated using conventional water treatment process.
So the city introduced advanced water treatment process including ozonation process and activated carbon processes. With those advanced system we could control the chemicals, such as 2-MIB and Geosmin efficiently.
This is the activated carbon. The black is the carbon material and we call that “activated” because the carbon has many microscopic pores inside of the carbon. That microscopic pores increase the surface area of the carbon, where chemicals can be absorbed into/onto microscopic pores.
The surface of the carbon is so large so seven grams of activated carbon has a surface area of one thousand cubic meters, which is the size of a football field.
This graph shows the efficiency of the advanced system. The red line shows the 2-MIB concentration in the Han River, and the blue line shows the concentration of 2-MIB in the treated water with conventional process.
As we can see, with conventional process we cannot remove much of the 2-MIB, but the green line shows the concentration of 2-MIB after treatment with advanced process.
As we can see even though we have higher concentration of 2-MIB in the Han River, the water treatment plant with advanced water treatment process could control the concentration of 2-MIB less than 10 microgram per liter, which is the guide line of the taste detection limit.