The removal of refractory dissolved organic carbon (R-DOC) in secondary treated water from a rural sewage treatment plant was studied using a hybrid-type constructed wetland system with a zeolite substratum from Jun. 2006 to Dec. 2008. Secondary treated water from a rural sewage treatment plant was supplied to this system. Average removal rates (%) of COD, DOC and E260 were 52, 43 and 22, respectively, during the experimental period by this system. R-DOC predominated in the secondary treated water and the ratio of R-DOC to total-DOC fluctuated from 53 to 84%. R-DOC was removed 38-66% after passing through the system in 2006. Result of DOM fractionation, hydrophilic acids (HiA) and hydrophobic acid (AHS) accounted for 30-40% of the total-DOM. The bases (BaS) was 19-27% and the hydrophobic neutrals ( HoN) and the hydrophilic neutrals (HiN) were present at only trace amount. The component ratio in R-DOM was similar to the total-DOM. No special removed fraction was observed in this study.

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The hydrous oxides of metallic elements are known to adsorb some ion species in aqueous media. In this study, ten Si-Al-Mg mixed hydrous oxide samples were synthesized using various Si, Al and Mg molar ratios, and the adsorption properties of these samples were evaluated in terms of ion adsorption rate. The adsorption equilibrium was attained only within 8 hours and completed at 24 hours for most of the prepared adsorbents. In particular, adsorbent No. 10, for which the molar ratio of Si-Al-Mg = 0.1:0.1:0.8, the greatest Mg ratio in the 10 adsorbents, was found to uptake large amounts of arsenite and phosphate ions. The Freundlich equation could be successfully applied to the isotherms for fluorine, boron, arsenate, arsenite, phosphate, selenate and selenite ions. The Freundlich parameter of 1/n ranged 0.1 – 0.5 for adsorbent No. 10 indicating that harmful ions could be easily removed from aqueous solution in broad concentration range.

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Japanese rose bitterling, Rhodeus ocellatus kurumeus, is an endangered freshwater fish in Japan. Both the expansion of the habitat of an alien subspecies, R. o. ocellatus, and the increased chances of hybridization between the two subspecies have threatened the genetic identity of R. o. kurumeus. To conserve R. o. kurumeus in Kagawa Prefecture, 17 populations were genetically monitored in 2006. Two individuals in a pond were found to harbor R. o. ocellatus type mitochondrial DNA through PCR-RFLP analysis. Then the contaminated population was transplanted to a closed Bio-top water system to prevent contamination in other ponds. Three-day pond drying was found to be insufficient to eradicate R. ocellatus.

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