The water then flows to 40 other filters, which are combinations of sand, anthracite, and carbon. These filters are regularly back-washed to purge the waste created by the bacteria. There is a visible difference in the waters of the river. The water flowing out of the plant has a bluish, clear tint to it, whereas further up the river, the water holds a browner tinge. The water is so pure that fish migrate to the area outside the plant.
Fishermen come from all around because the fish are so abundant.
The fish have even swum up the pipes which discharge the water from the plant. They can be in the sedimentation basins. Occasionally, one of the fish may swim too far into the plant, and gets caught in the filters. The leftover sludge is then dealt with. The sludge still contains a great deal of water.