Abstract
To prevent the elution of lead from water pipes, the adjustment of the pH of purified water is effective. However, substantial data on the effect of pH adjustment on purified water are not yet available. Thus, to examine the effect of the pH adjustment performed by the Ushikubi Filtration Plant, the relationship between pH and lead concentration was analyzed from past data. As a result, the lead elution rate was found to decrease with pH adjustment; however, the rate also decreased year by year. Thus, the pH adjustment effect is still unclear. It was considered that faucets that elute a very small amount of lead in the same manner were distributed in Japan and that pH influenced such lead elution. Then, using the nationwide water supply statistics of 2003, the data of purified water quality were sorted into ten groups by pH, and mean lead concentration and lead detection rate were calculated for each group. As a result, relational formulae relating pH, lead concentration and lead detection rate were obtained. These equations will be useful for assessing the effects of decreases in lead concentration and lead detection rate induced by pH adjustment.
