Then one fateful day they merged to form one, each complimenting the other as they became a strong, productive unit. Judging from their results, this could be the beginning of a beautiful friendship. The coupling was inspired by state and federal laws requiring miners to restore natural vegetation to areas they've disturbed. Tailings piles, especially those leached with sodium cyanide to extract gold as at the Ryan Lode Mine outside Fairbanks, are about as fertile as cement. At Fairbanks' sewage treatment plant, waste water from such sources as toilets, showers, sinks and the occasional draining of a city swimming pool enters via a huge pipe at the rate of about 7,000 gallons a minute at midday.
Incoming sewage is screened and aerated with oxygen to stimulate waste-eating bacteria.
Heavier solids settle to the bottom of large tanks, and, after as much water as possible is squeezed out on a conveyor belt, sludge happens. Every day the Fairbanks plant generates 25 cubic yards, about two and a half dump truck loads, of the black, clumpy, pungent substance. In the past, the sludge had been piled outside the plant. Now it's hauled off and burned. In an effort to make use of the sludge, Charlie Knight, a University of Alaska associate professor of agronomy, and graduate student Trish Willebrand teamed up with the mine in September 1993, mixing different concentrations of sludge into the tailings piles with a rotary harrow, a piece of farm equipment that works like a rototiller.