Freshwater mussels are being used to clean up dirty rivers in Japan. What’s amazing about these mussels is that they are capable of cleaning almost 180 liters of water in a day. They consume diatoms and other phytoplankton feeding on nitrogen and phosphorus and clean the water as a result of this process. This has improved the water quality of some extremely dirty rivers like the Dotonborigawa River of downtown Osaka. However, the water is still not clean enough to swim in. Some of the mussels produce pearls.
In March 2008, clams were taken from Tokyo Bay for the first time in 40 years. The restoration of clamming which had come to a halt in 1969 because of water pollution shows that water quality in Tokyo Bay is showing significant improvement.
The Kyu-Otagawa River, which makesit way through the middle of Hiroshima, was known for its contaminated water, sludge and foul smell. A few back, it was cleaned using “infiltration pillars” made of used coal ash from power plants. These decompose sludge, rid the waters of odour and above all, clean the water enough for life to thrive in it.