都市下水の養殖ノリの生育に及ぼす影響に関する研究 ＩＶ 養殖ノリの生育に及ぼす塩素殺菌都市下水処理水の影響

Abstract

The effects of chlorinated effluent of activated sludge treatment on the growth of Porphyra yezoensis were investigated with different chlorinated effluent-dosed culture media and different chlorine-dosed, diluted Provasoli's Enriched Seawater (PES) culture media as a control, by means of a shaking culture. To clarify the effect of the chlorinated effluent on the Porphyra thalli, the length of thalli were measured every two days, and the number of dead cells in a thallus were counted under a microscope 4-10 days after the start of the culture followed by an erythrosine staining. Initial chlorine concentrations which manifested a 50% growth effect and 50% dead cell in chlorinated effluent-dosed culture and chlorine-dosed diluted PES culture were 0.025-0.035mg Cl2/l and 0.06mg Cl2/l, and 0.75-0.95mg Cl2/l and 1.5-3mg Cl2/l, respectively. The growth effect and dead cells manifestation were dependent on the initial chlorine concentrations in both cultures. It was found by the amperometric method that chlorine was free chlorine in the diluted PES culture and combined chlorine in the chlorinated effluent-dosed culture. Although both residual chlorines disappeared with the passage of time, the removal rate of combined chlorine was slower than that of free chlorine. The above mentioned results suggest that the strong toxicity may be caused by the reaction products of chlorine with organic substances in the effluent.