I found this a while back:
http://stillgettingready.blogspot.com/2013/09/drinking-swimming-pool-water-in-case-of.html
Once the pump and filtration stop a swimming pool will turn a dark green with streaks of light green, orange and black within about 2 weeks. You can dump a heavy dose of shock in it to slightly prolong but without movement the water turns bad quickly.
I found this out when someone stole my pool pump, filter and the electrical box off the side of my house.
The conclusion of the man who wrote that article you posted with a link, concluded the same thing I have after reading and studying drinking water from swimming pools. He concluded putting swimming pool water through a Berkey would make it good drinking water. I have a Big Berkey and that is what I plan to do when my other sources are short. The swimming pool in my group of townhouses holds 250,000 gallons and it will keep filling with water when it rains which is fairly often here except in August.
I also have rain collection methods at my house to put through a Berkey but that swimming pool is my Plan B, C, and D.
I’m always looking for more confirmation about swimming pools.
Isn’t it also possible to purify by distilling it, as if it were sea water, and the copper, etc would end up as salts?