cyanobacteria warning

from what I’ve read about this in the past, many (most) back packer water treatment systems are not effective against this. the issue is the toxins produced, not so much the algae or bacteria. if the chemical toxins are not removed from the water it is still dangerous to drink.

I’m sure someone more knowledgeable will chime in soon with specifics.

If I recall, the First Need filter seemed to do a good job of removing cyanobacteria but I’m not sure if there is any more recent info about it. Here’s an 8 year old publication

Eon’s ago, when I was was playing around with a First Need filter in my Scout Troop, I decided to filter Pepsi through the thing.  I was shocked to see clear, un-carbonated, sugar water come out. That water, plus the next 20 gallons of water had a sugary taste to it.

Not a bad treat for a bunch of growing Boy Scouts!

https://www.epa.gov/sites/production/files/2014-08/documents/cyanobacteria_factsheet.pdf

See pages 7-8

According to the EPA, nanofiltration (0.001 to 0.01 microns) should take care of the toxins (extracellular microcystins) with frequent backwashing. It also looks like granular activated carbon (GAC) inactivates them, as well as chlorine (but the latter is pH dependent). UV is also supposed to be effective, but effective dosage is “impractical”.

I’d probably lean toward carbon filtration followed by nanofiltration.