- Just an idea -
Here's the idea:
If you use a staged liquid anaerobic/aerobic waste-water treatment system, one bi-product is Hydrogen Sulfide gas.
The geysers at Yellowstone have a sort of bacteria that
feed on sulfurous compounds in the
water.
If you bubbled air, and separately, the Hydrogen Sulfide gas up through some watery environment otherwise engineered for those bacteria, becoming partially dilute, soluble, or saturated in that watery mix, maybe the bacteria would be able to feed partially on that soluble sulfur, also having whatever else they need (air/oxygen and food) reducing its content, and a slightly purer hydrogen gas might result.
Maybe This, together with oxygen could be fed through a crude Hydrogen Fuel Cell ?
In this way, a waste-water treatment process could also provide electricity. - ?
It could also be a part of a dual system - (see also my other Hydrogen Sufide/Fryolator froth fuel topic)