The purpose of this research is to evaluate the removal efficiencies of CODCr and color for the dyeing wastewater by the different dosages of ferrous solution and H2O2 in Fenton process. In the case of H2O2 divided dosage for the Fenton's reagent 7:3 of H2O2 was more effective than 3:7 to remove CODCr and color. The results showed that CODCr was mainly removed by Fenton coagulation, where the ferric ions are formed in the initial step of Fenton reaction. On the other hand color was removed by Fenton oxidation rather than Fenton coagulation.
The removal mechanism of CODCr and color was mainly coagulation by ferrous ion, ferric ion and Fenton oxidation. The removal efficiencies were dependent on the ferric ion amount at the beginning of the reaction. However, the final removal efficiency of CODCr and color was in the order of Fenton oxidation, ferric ion coagulation and ferrous ion coagulation. The reason of the highest removal efficiency by Fenton oxidation can be explained by the chain reactions with ferrous solution, ferric ion and hydrogen peroxide.
As an effort to clarify the ecosystem of Osaka Bay, a semi-enclosed coastal area under the influence of stratification, a three-dimensional water quality model with combination of the baroclinic flow model and primitive eco-system model was constructed. The proposed model succeeded in simulating the time-depending flow and density structure and the baroclinic residual currents in Osaka Bay. In present study, we tried to improve the model by taking account of the benthic-pelagic interaction and exchange of nutrients between sea bottom sediments and overlaying water. On vertical structure, the model consists of 13 layers of water and eight layers of sediments.
Long-term prediction of water quality was conducted from 1964 to 1985. This period is characterized by rapid water pollution and its decrease by the cutoff reduction of COD and P flowed into Osaka Bay. By combining the sediment model into original model, the numerical model was confirmed to shows more reasonable results in simulating the water quality in Osaka Bay.
The rapid industrialization and urbanization in Osaka Bay have produced many serious water pollution problems since the 1960s. A symbolic phenomenon is algae bloom (red tide), which occurred 53 times in 1976. The special law was enacted in 1973 and a number of administrative steps were taken, such as cutting COD loading, reductions in phosphorus (P) and restriction of land reclamation. As a result, the pollution of Osaka Bay has gradually been reduced, and the environment has been improved to some extent. In this study, to analyze the relations between water qualities as well as a social, economic activity by the coastal zone, the water quality data in Osaka Bay of 70 years past since 1921 were collected. Data such as population, livestock, fertilizer, industrial product etc. were also collected for estimating nutrients flowing into bay from land. It was found that the water quality was changed of a similar trend of estimated nutrients load, with delay of about four or five years.