An amazing prototype device which can generate electricity from waste water produced by US researchers. Using a method called reverse electro dialysis (RED), fresh water and salt water are placed in alternating chambers separated by membranes, and an electrochemical charge is created. The ammonium bicarbonate solution would be constantly recycled, using waste heat from local industry.
The Penn State team says RED technology is problematic because of the large number of membranes required, and because power plant life have to be situated by the sea. The major application right now is in waste water treatment where you could effectively treat the water, but also gain some additional power from waste heat.