EVALUATION OF THE TOXICITY REDUCTION FOR TAMAGAWA NEUTRALIZATION TREATMENT FACILITY USING WET METHODS

Abstract

 A strongly acidic spring with a pH 1.2 that gushes out from the large spout of Tamagawa hot spring in Akita Prefecture flows into Lake Tazawa, aquatic organisms became extinct, including the endemic species of Oncorhynchus kawamurae. As a countermeasure, the Tamagawa Neutralization Treatment facility is in operation, but pH value of Lake Tazawa are lower than the water environmental standards, and the aquatic organisms of the past has not returned. Therefore, in this study, we used the WET methods to evaluate the toxicity reduction effect on aquatic organisms in four stages: before and after neutralization at the Tamagawa Neutralization Treatment facility, and when the neutralized water was raised to pH 6.7 and pH 8.5.

 As a result, a reduction in toxicity was observed for all three types of aquatic organisms as the pH increased, but the current neutralization treatment was insufficient to reduce toxicity to aquatic organisms. In addition, the concentrations of F, B, Al, As, and Zn were measured to clarify the behavior of toxic substances groups as a result of pH changes. The current neutralization process does not remove toxic substances, and it has been revealed that increasing the pH will remove them by precipitation, reducing their toxicity to aquatic organisms.