A PROPOSED METHOD OF WATER QUALITY COUNTERMEASURE AND INVESTIGATION OF POLLUTION MECHANISM BY WATER AND SEDIMENT QUALITY SURVEY IN CLOSED WATER AREA

IN CASE OF EDO CASTLE OUTER MOAT

Abstract

Edo Castle outer moats (hereafter is outer moat) has problems of bad smell and deterioration of the landscape by the inflow of sewage untreated water during the time of rainfall and occurrence of Blue-green Algae Blooms. To elucidate the water pollution mechanism in the outer moat, we conducted filed observation of water quality and a laboratory experiment using the local sediment. As a result, the concentration of nutrient, organic matter and Chlorophyll-a were extremely high levels. Also, limiting factor of the Blue-green Algae is nitrogen by TN/TP ratio. Then, we focused on countermeasures to prevent blue-green algae from growing by flushing out them and calculated the required volume of water in the outer moat. Furthermore, we introduce a new framework which solve as probability theory considering an uncertainty that the growth rate of the algae contains.