By Matt Vasilogambros and Kevin Hardy for Stateline.Broadcast version by Kathleen Shannon for California News Service reporting for the Solutions Journalism Network-Public News Service Collaboration After an Orange County resident flushes her toilet, the water flows through the Southern California community’s sewer system, meanders its way to the sanitation plant, has its solids removed, is piped to a wastewater recycling facility next door and undergoes three different purification processes until it is clean enough to drink. “It tastes like water,” said Mehul Patel, executive director of operations for the Orange County Water District’s project, after taking a gulp from a clear plastic cup at the sampling station, as he stood outside the final purification process facility on a warm afternoon earlier this month. “It’s just like any other water, but it’s gone through a lot,” he said. ...
You’re very right about prions. But there’s more passing through reverse osmosis membranes than meets the eye.
Size cut-off is not the sole trans-membrane transport process. The material of some membranes allow the diffusion of some molecules - roughly, hydrophobic membrane materials allow diffusion of hydrophobic molecules… its more specific than this, though.
There are targeted studies to assess the removal of micropullutants that show that some micropollutants can pass membranes even though their size is bigger than what would reasonably be expected to be retained.
I don’t know anybody studying this with broad spectrum techniques that uncover unknown-unknowns.