Removal of metals related to radionuclides (Sr, U) and heavy metals (Co, Cu, Hg, Cr and As) present in aqueous solutions using photosynthetic bacteria immobilized porous ceramic, which can be recovered with an electromagnet, were carried out under aerobic dark condition. Among the photosynthetic bacteria tested, Rhodobacter sphaeroides SSI showed the highest removal activity for such metals with immobilized ceramic. The percentage of removal of 20 mg/l of Sr, Co and U were as high as 82%, 58 and 95, respectively after 6 days of treatment. The COD and phosphate present in the aqueous solution were simultaneously removed at high efficiency of over 90%. With a pure culture system, strain SSI can adsorb 98% of U on and/or in the cells from culture liquid during 6 days of aerobic growth. These pieces of immobilized porous ceramic could also remove Cu, Hg, Cr and As in the same system.

Removal of cooking oil from the domestic wastewater was carried out by immobilized photosynthetic bacteria, Rhodobacter shaeroide S (S) and R. shaeroides NR-3 (NR-3). The microorganisms were immobilized in sodium alginate (2%) or agar (2%). We treated 50 g of cooking oil suspended in artificial sewage wastewater under anaerobic dark conditions in a 15 l acrylic vessel. Results show that after 6 days of batch treatment, 74.2, 58.2 and 15.8% of oil was removed with the alginate-immobilized S, NR-3, and control, respectively. Relatively larger accumulations of volatile fatty acids such as propionic and acetic acids were observed in the control experiment compared with that in the immobilized cell (alginate and agar) experiment. In addition, continuous treatment of oilcontaining wastewater was carried out with agar-immobilized S at a fixed dilution rate of 0.4/day. These results indicate that 96% of the oil was removed from the wastewater, and the maximum removal rate of oil reached approximately 3.83 kg oil/m 3 /d.

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