Abstract
Effect of NH4-N in dilution water on BOD concentration of water treated by johkasou, which has some high concentration of nitrogen, was investigated. Three kinds of dilution water, that is distilled water, standard dilution water without adding NH4Cl and standard dilution water were used for BOD measurement.
BOD of such water that was in the tank for biological treatment in which nitrification reaction progressed and that contained some sludge showed a high weight of N-BOD. NH4-N in dilution water contributed greatly to N-BOD when the dilution factor was large. It was found that nitrification of NH4Cl added in the standard dilution water processed in the early stage of BOD decomposition.
Concentration of (NH4+NOx)-N resulting from water in the BOD bottles was calculated based on data obtained in the previous surveys. It seems that no inorganic nitrogen was needed to add into the standard dilution water, because nitrogen concentration of water measured in this study was found to be higher than that in the standard dilution water.
