Basically use dirty water, finely filter it, such that only things as big as phages remain. Put that liquid in a solution of bacteria you want to treat. Filter it again, repeat... In the end you should end up with some phage solution which specifically attacks the bacteria. If these phages don't work anymore, find new ones.
This reminds of the universal cure to disease being a bullet [1].
Phages are promising. That doesn’t mean they can’t hurt you [2].
The biggest hindrance is that the western process of developing and releasing new medicine is ill-suited for phage treatment.
…as evidenced by the booming phage industry somewhere in the east?
(The weird thing is this railing against western medicine or whatnot is usually a dead ringer for pseudoscience. Yet phages are a scientifically valid thereaupeutic route [1].)
How is this different from antibiotics?
Nothing about phages makes them not worth developing. Exhibit A: they’re being researched and developed.
And this makes them “not worth…developing” why?
(The comparison to antibiotics was that the antibiotic-bacteria system is coevolving too. Exhibit A: TFA on antibiotic resistance.)