Masayuki Fukagawa

A model for membrane bioreactor process based on the concept of formation and degradation of soluble microbial products.

A mathematical model of soluble microbial products (SMPs) formation-degradation was established based on the activated sludge model no. 1 and was applied to the membrane bioreactor process with high concentration of activated sludge under intermittent aerobic operational condition. The simulation results were in good agreement with the experimental data which indicated that the coefficients used in the model could successfully describe the treatment performance. The most advantage of this modified model over the conventional one was that the significant importance of SMP existence was demonstrated and the model provided an reasonable comprehension for SMP concept. The present study demonstrated that SMPs contributed most to the organic matter in the effluent, and the results coincided well with the observations of many other researchers.

Fermentation Wastewater Treatment in a Membrane Bioreactor

Performance of highly concentrated activated sludge in high strength fermentation wastewater treatment coupled with rotary disk type UF membrane is reported. The maximum MLSS and MLVSS concentrations obtained in this study were 15.2 g l−1 and 13.0 g l−1, respectively. The performances of TOC and NH4-N removals were quite well. Most of the soluble organic matters in fermentation wastewater were readily biodegradable. Nitrification increased quickly and varied between 60%–100%. However, denitrification was around 20% throughout the experiment. A series of batch culture tests showed that the maximum specific nitrification rates (SNR) slightly decreased, on the contrary, the maximum specific denitrification rates (SDNR) slightly increased. The actual SNR were between 0.5 and 1.0 mgN gMLVSS−1 hr−1 and the actual SDNR were lower than 0.5 mgN gMLVSS−1 hr−1 as this process was operated under continuous aeration condition. In addition, specific activities of sludge estimated by INT-dehydrogenase activity were almo...

Application of ORP Control for Nitrogen Removal in Highly Concentrated Activated Sludge Process

A laboratory-scale experiment was carried out for fermentation wastewater treatment by intermittent aeration process using oxidation reduction potential (ORP) as a control parameter. A high concentration of activated sludge was retained in the reactor by ultrafiltration (UF) membrane during the experimental period. For simultaneous carbon and nitrogen removals, the lower and upper ORP limits should be −50 mV and +175 mV respectively. The lower total organic carbon (TOC) and total nitrogen (T-N) concentrations in the effluent was observed, which demonstrated that ORP control method was suitable for high strength fermentation wastewater treatment in a single bioreactor by intermittent aeration process.

Eutrophication control in the Seto Inland Sea

The Seto Inland Sea, surrounded by the four large islands of Honshu, Shikoku and Kyushu, is famous for its scenic beauty and coastal fishery. However, the beauty of this area has been threatened by a high concentration of human population and industry which contribute to water pollution and eutrophication problems. In this study, we examine the present water pollution problems of this area; we have studied the history of water pollution in the Seto Inland Sea, the influx of nutrients into all sections of this area and the relationship between eutrophic levels and fishery productions in each section of the Seto Inland Sea. We have also analyzed the secondary organic pollution which is a result of the primary photosynthesis production and the comprehensive eutrophic situation of the sea and each of its sections, in comparison with other coastal seas in Japan. From the results of this evaluation, we propose the following four strategies for eutrophication control in the Seto Inland Sea: (1) Elimination of nitrogen (N) and phosphorus (P) discharging loads by means of controlled chemical fertilizer consumption and recycling of human and livestock excreta as fertilizer (as a conclusion of the budget of N and P in Japan); (2) Consolidation of treatment facilities for the point sources of pollutants such as domestic sewage and industrial waste water; (3) Diversion of the discharging N and P loads from the Seto Inland Sea into the adjacent open sea areas of Japan which have a larger carrying capacity through the exclusion system such as a sewer system (through comparison with each adjacent sea area of Japan); (4) Dredging of sediments over the polluted zones.