2023 Volume 79 Issue 25 Article ID: 23-25040
We studied the effects of discarged sewage water during the seasonal management operation of sewage treatment on the growth condition and quality of Nori laver, by investigating water qulity and the content of nitrogen and phosphorus, quality (color tone, L* value) in Nori laver around the sewage discharge outlet and Nori cultivation grounds located in Hakata Bay.
As a result, we found that the L* value, which is indicated of the quality of Nori laver, was significantly correlated with nitrogen and phosphorus content of Nori laver, and estimated that Nori laver was of the excellent quality with nitrogen and phosphorus content of 5, 0.2 wt%-dry or higher, respectively. Although there remained the problem in quatifying the concentration of inorganic phosphorus required for Nori laver, we suggested that even if the concentration was lower than 0.0124 mg/L, which was the index required for the growth of laver according to Fukuoka Prefecture, it was sufficient for the growth of Nori laver. Fuerhermore, we found that discharged sewage water during seasonally sewage treatment operation was caused the delay in the time when the discoloration of Nori laver was caused, and the suppression of quality degradation at the location near the sewage discharge outlet and the effect was likely to occur in the Myoken cultivation grounds located on the west side of the discharge outlet. In addition, we suggested that increasing the supply of inorganic phosphorus by seasonally management operation was one of the factors of the effects.
