When we used seawater effluent from the seaweed processing plants (No. 1–4), the initial numbers of bacteria in the effluent samples were 7.5 · 105 (No. 1), 5.6 · 106 (No. 2), 3.0 · 105 (No. 3) and 2.4 · 105 (No.4) cfu/ml. When we treated for a short duration, the samples flowed into the reactor vessel but did not circulate. Each 1 l sample was allowed to react for 10 min.The bacteria populations in samples of No. 1 and 3 quickly decreased but remained at more than 103 cfu/ml (Fig. 4a). However, the bacterial numbers in samples No. 2 and 4 slowly decreased to less than 102 cfu/ml(Fig. 4a). Although concentration of protein and salts in the initial samples were compared, there were no notable differences. The differences in the effect among the samples may be due to the various individual components in the samples. The effluent samples were discolored
(Fig. 4b). The phycoerythrin and phycocyanin that
causes this color in the samples were bleached by the
photo-catalytic reaction. In experiments using ultraviolet
light alone without the TiO2 catalyst (data not
shown), we found culture cell numbers decreased rapidly.
However, no oxidation of the organic material in
the effluent occurred. These results suggested that
photo-catalytic is possible to sanitize industrial bio-effluent.
In this study, disappearance of the whole cells with
the reactor was not observed under microscope. However
the outline of most cells was blurred at 30 min after
TiO2 reaction (data not shown). Cells might disappear
by more reaction.