Analysis of the origin of soluble COD in Lake Sanaru

This study intends to investigate the origin of Sol-COD by analyzing the water quality data and the amount of detergent consumption in the Lake Sanaru region,located at Hamamatsu City in Japan. It was found that there is a correlation between the total COD in the lake and the sewer coverage in the upstream region of Lake Sanaru. This fact implies that the water quality of upstream rivers receiving untreated wastewater from homes would greatly affect the water quality of the lake. Since the value of Sol-COD in the rivers is close to that of Lake Sanaru, the main origin of the Sol-COD was supposed to be the organic components in the river water especially those of detergents, because the Sol-CODof detergent didn’t decompose completely.Thus, the amount of detergent emitted in the upstreamlakeregion was determined using the public data of the pollution from the sewer system and the national average of detergent consumption. The calculated value of the detergent concentration agreed very well with the one measured in the upstream rivers, meaning that detergents strongly affected water quality in upstream rivers and also the majority of Sol-COD in Lake Sanaru.