RESTRAINT EFFECTS OF 2-MIB CONCENTRATION INCREASES DUE TO TOTAL PHOSPHORUS MANAGEMENT IN THE UPPER KINOKAWA WATERSHED
Keywords:Kinokawa River, Off-flavor tap water, Total phosphorus, Mass load analysis, River water quality analysis, Distributed hydrological model
The off-flavor taste of tap water due to 2-methylisoborneol (2-MIB) is caused by blue-green algae.
This is one of the water quality problems associated with high nutrient loads, such as those found in the Kinokawa
River, with drains the southwestern part of the Kii peninsula in Japan. Water quality monitoring data showed that
2-MIB tended to increase when total phosphorus (TP) concentration exceeded 0.02 mg/L. This study employed
mass load and river water quality analyses coupled with water runoff analyses to examine ways of mitigating TP
load in river water. In this study, it was revealed following things. (1) TP mass load could be reduced by
approximately half if the industrial drainage volume standards defined in the Water Pollution Control Law were
more stringent. (2) TP concentration could be decreased by 41% in response to TP mass load reduction and by 5%
in response to an increase in river flow rate. (3) TP mass load reduction combined with an increase in river flow
rate could reduce TP concentration to less than 0.015 mg/L and prevent increases in 2-MIB in tap water.