When my scout troop is teaching the Emergency Preparedness merit badge, we often do an exercise on bulk treatment of water beyond what is practical to filter with the portable filters we take on backpacking trips. We use alum as a flocculant, then sand to filter, then battery-powered UV sterilization (while noting that leaving clear water out in full sun for a few hours will accomplish the same dose as stirring a UV lamp through a bucket for a minute or two). Alum isn't exactly a common household item these days and the UV lamp certainly isn't, but it does make for a cheap and compact kit that can treat a lot of water with relatively little time and effort.

> Alum isn't exactly a common household item these days

You can often find it in the spice section. People use it to make pickles.

McCormick/Schilling sells it, among other major brands.

Walmart sells "Hoosier Hill Farm" brand for about $15/pound.

My point was more that it isn't something people are likely to already have on hand at home. It's certainly readily available and extremely cheap for this purpose, but you need to actually buy some before a disaster hits.

Depends on the family!

Hoarding the clearance pickling supplies after the season is over is a long tradition in my family. :)

Chlorine will kill giardia. You just have to wait somewhat longer.

Giardia is definitely present in Pakistan, where this is being manufactured.

Unfortunately it seem to not to work in Chinese giardias.

Giardiosis happen rather routinely even in places like Shanghai. Personal experience.

The quality of tap water in Shanghai is pretty bad even by Chinese standards - there is a reason why boiling water is the norm.

I picked up a case of Crypto during a day trip to Milwaukee for a lunch meeting back in the 90s (they had a water treatment issue).

0/10, would not recommend.