NASA astronauts need continual supplies of freshwater, so it should come as no surprise that the work of NASA researchers has frequently focused on water filtration methods. In fact, one of the Space Technology Hall of Fame inductees admitted in 1988 -- the first year the honor was offered -- went to ongoing research in this field.
Researchers in the 1970s and '80s discovered and developed water filtration techniques that took advantage of unique traits possessed by water hyacinths. While in most cases water hyacinths are considered to be an invasive species, the plants have also shown great potential in the field of wastewater treatment.
Conventional water treatment plants require expensive equipment and valuable energy to run, but treatment plants using water hyacinths require little of either. The hyacinths need no artificial heating and little aeration; they can survive in heavily polluted wastewater with no problem; and they grow at exceedingly rapid rates. It works because the hyacinths have a mutualistic relationship with certain bacteria that live on their many root hairs. The bacteria break down waste and turn it into nutrients the plants can digest. The hyacinths are also excellent at removing heavy metals and toxic chemicals from the water that other treatment methods aren't effective against, so the end result is incredibly clean.