WATER QUALITY IMPROVING METHOD FOR NATURAL WATER SYSTEM

摘要

PURPOSE:To provide a water quality improving method for natural water system with which not only decomposition or nitrification of BOD and NH3 is carried out but also decomposition of nitrogen of nitric acid and nitrous acid is carried out effectively and SS is scarcely generated. CONSTITUTION:A filtration bed 1 composed of sand or pebbles is formed in a natural water system, a circulation flow from the uppr side to the lower side of the filtration bed 1 is formed, the circulation flow speed is so controlled as to suppress the dissolved oxygen concentration in the outlet circulation flow of the filtration bed 1 to 1.5ppm, and oxygen is taken in by photosynthesis in the surfacial part of the filtration bed by plant plankton and a part of the plant plankton is made to be a prey of fishes and shellfishes and nitrification and decomposition of organic substances are carried out in the middle part of the filtration bed 1 by aerobic microbes using the oxygen. After that neutralization and denitridation by anaerobic microbes are carried out in the lower part of the filtration bed 1, treated water is collected by a water collecting pipe 3 laid in a supporting pulverized rock layer 2 which supports the filtration bed 1 and the water is discharged to the object water system to be treated through a water collecting pit 4 connected to the water collecting pipe 3.