Abstract
In the first report of this paper, we confirmed that ammonium ion (NH4+) was concentrated into the product water if the seawater distillation was carried out by using the seawater polluted with ammonia. Besides this evil influence, the existence of NH4+in seawater was supposed to accelerate the corrosion of the plant and the dissolution of the metallic constituent materials into the product water. By adding ammonium chloride to the make-up line of a 3,000 m3/day multistage flash evaporator, we examined the change in time of the metallic ion concentrations in the product water and in the effluent brine of the plant (Figs.-1, 2 and 8).
Iron, copper, and zinc ion concentrations in the product water decreased with an increase in NH4+concentration when NH4+concentration was comparatively small (Fig.-1). This might be due to a decrease in the corrosive power of the product water caused by its pH elevation. When NH4+ concentration increased more, the concentration of copper ion distinctly increased; total ion concentration continued to decrease; and the data of zinc ion became to show much fluctuation (Fig.-2). These data were analyzed by plotting them against the pH and NH4+ concentration (Figs.-4-8).
Iron and copper ion concentrations in the effluent brine increased in line with an increase in the concentration of NH4+ (Fig.-9). Main reason for this increase was supposed to be the lowering of the pH value of the circulating brine, but the phenomenon was too complicated to do a precise analysis.
