The application of seawater desalination technology using a reverse osmosis (RO) membrane has been expanding because it requires less energy compared with other distillation methods. Even in Middle Eastern countries where energy costs are lower such as Saudi Arabia, UAE, Qatar, and Kuwait, almost all desalination plants where only water production is required have adopted the RO method. However, large plants in excess of half mega-ton size are required, and Seawater Reverse Osmosis (SWRO) operation lacks reliability due to heavy biofouling and large amounts of briny discharge contaminated with chemicals. For reliable desalination systems with lower environmental impact, membrane-processing technology, including biotechnology (such as marine bacteria), has been examined as national research in Japan in the “Mega-ton Water System” project. We examined the influence of chlorination on marine bacteria using the fluorescence microscopic observation method and found that the effect of chlorination is limited. Chlorination sterilization triggers biofouling and sodium bisulfate (SBS) addition as a de-chlorinating agent also triggers biofouling, so a process with no chlorine or SBS addition would reduce biofouling. As polyamide SWRO membranes have low chlorine resistivity, such a process would enable longer membrane life in real plants. We used a biofouling monitoring technology, the Membrane Biofilm Formation Rate (mBFR), to design a process that involves no chlorine or SBS addition and verified it in the Arabian Gulf Sea, of Saudi Arabia, which is one of the most difficult and challenging seawaters in which to control biofouling. Furthermore, by minimizing the addition of a sterilizer, the desalination system became more environmentally friendly.

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Two different mixed cultures, which degrade terephthalate at 50 degrees C and pH 8, were isolated from a wastewater treatment plant. These were useful for the treatment of wastewater containing a high concentration of terephthalic acid (TPA). Each mixed culture included a TPA-degrading bacterium, strain K1 or Pseudomonas sp. C4S, and another bacterium unable to degrade TPA, the as-yet unclassified strain K3 or Bacillus sp. C4B. In axenic culture, K1 and C4S showed poor growth even in a medium supplemented with yeast extract and tryptone. On the other hand, when co-cultured with the co-isolate from the mixed culture which is unable to degrade TPA, the growth was enhanced. Moreover, several bacterial strains in our stock culture collection showed the ability to improve the growth of both TPA-degrading bacteria. A mixed culture of strains K1 and K3 exhibited rapid growth and TPA degradation in a chemically defined medium, suggesting that the mixed culture system would be applicable to the treatment of wastewater containing TPA.

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