Today started a bit more normally, i.e. without a scavenger hunt for our professor. We first visited the new Seoul City Hall, a flowing 12-floor glass building that houses the metropolitan government. I did a bit of sketching of the building from a few angles, and my sketches were pretty poor, but sketching is about looking, not drawing. We took a tour of the building, then departed for the Jongno-gu District, where, after a hotpot (?) lunch, we visited the Arisu Ttukdo water purification plant. After a tour there, we had Korean BBQ for dinner before going out to experience the city at night. Back to the water though. It was an impressive site, interesting to walk around and take a look at the multi-step purification process. It was also a bit funny to see that the previous purification system, which was simply a sand filtration process, removed over 99% of the bacteria in the water. In the modern system, an additional 7-8 steps are performed to work away at that remaining 1%. Comparing to what I know, this was certainly very different in scale from the Pittsburgh Water Treatment Plant that is situated in Aspinwall PA, just a few minutes drive from my house back home.

As it turns out, Ttukdo is just one of six water treatment sites that serve the city of Seoul. Back home, the Aspinwall plant is the only facility for the entire Pittsburgh region. This came as a surprise to me, obviously Seoul is many leagues above Pittsburgh in resource needs, however it didn’t occur to me that they would have multiple regional facilities rather than one. A quick google finds that New York City has 14 plants of which around half operate at or below the capacity of our Aspinwall plant, so my surprise is really directed at Pittsburgh. Since pumping water is a feat made more difficult by the extremely hilly terrain, and since there are multiple sources of water (three rivers), it would make sense to have a few smaller treatment plants, both for efficiency and for redundancy – if one goes offline, the entire city is not suddenly without water.

Part of the reason may be that historically, the Allegheny River was relatively cleaner than the other two rivers (Monongahela, which was where most of the industries were, and Ohio, which is fed by the Mon). Therefore, if a treatment facility were to be built in the early 1900s, it would have to be on the Allegheny, therefore it may not have made as much sense to have multiple on one river. In terms of wastewater treatment, in Pittsburgh, wastewater was discharged directly into the rivers until 1946 when ALCOSAN was built on the Ohio river, far downstream of Aspinwall.

Back to Seoul though, thinking about Pittsburgh in this way does spur the question of how Seoul deals with six purification plants, wastewater treatment and discharge, and heavy industry with just one river, without compromising the water supply. I still want to do some research on this, especially because my first google searches seemed to suggest that at least one wastewater treatment plant (Jungnang) is farther upstream of the main city.

One main problem with having wastewater discharge upstream of the freshwater treatment plant is in the case of overflows. Pittsburgh, and many other older cities, have a combined sewer system, which means that in cases of heavy rain, sewers overflow directly into the rivers. As it turns out, Seoul also has a combined sewer system, meaning that having separate areas of the river for freshwater intake and wastewater (even treated wastewater) discharge is that much more important.

Or just start doing some Chicago River level geoengineering.

Anyways, that’s all from me. Not well organized but it is what it is. More tomorrow.