Abstract
Influences of human excrement (night-soil) on water quality in Minami-Asakawa River were studied during July 26-27, 1979, using coprostanol as an index of fecal pollution.
Concentrations of coprostanol were 0.0-2.7μg·l-1 (mean 1.6μg·l-1) at MA-3 (midstream) and 0.03-12.2μg·l-1 (mean 4.0 μg·l-1) at MA-5 (downstream). Higher concentrations were observed in sewage water flowing into the river between MA-3 and MA-5 : 4.3-61.21μg·l-1 (mean 22.9 μg·l-1) at Sw-1 and 2.2-43.4 μg·l-1 (mean 11.8 μg·l-1) at Sw-2. Coprostanol seemed to be derived from waste water mainly from septic tanks.
It was found by budgets between MA-3 and MA-5 that coprostanol tends to change from particulate to dissolved form during river flow. However, apparent decrease of the total amount was not observed, and therefore coprostanol is considered to be fairly resistant to bacterial attack and behaves as a conservative substance in the river.
It was suggested that organic loadings of night-soil origin were only 2% of the daily loadings of total organic carbon at MA-5, and great parts of remaining loadings were due to untreated domestic waste water.
