In drinking water treatment process including ozonation and biological activated carbon (BAC) filtration, the treatment capability of BAC filter was compared with that of biological filter with a carrier having no adsorption capacity, to clarify the effect of adsorption and biodegradation activity on the mechanism in BAC filtration. Trihalomethane formation potential (THMFP) and E260 were highly removed by the combination of ozonation and BAC filtration. On the other hand, the biological filter had generally lower removal potentiality compared with BAC filter. However it appeared that higher removal potentiality close to that of BAC filter was achieved by the combination of ozonation and biological filter at high water temperature. Number of bacteria on BAC was little different from that on the medium for biological filter.
The removal potentiality of THMFP and E260 in the combination of ozonation and BAC filtration was little different from that in BAC filtration without ozonation. However the adsorption load for BAC was decreased by oxidation and improvement of biodegradability at preozonation.

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Treatment process have been developed for wastewater from polyvinyl chloride(PVC) manufacturing plant, combining several technologies. The wastewater was ultra-filtrated to remove suspended solids of PVC and cellulose which was added as a dispersing agent. The wastewater, passing through the filter, which contains chemically and biologically refractory substances, was electrochemically oxidized to convert them into biodegradable substances, followed by being treated biologically with submerged biological bed. The process performance was obtained as overall removal of 98% in TOC, 95% in COD and 99% in BOD.

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Experiments using six outdoor experimental ponds equipped with a continuous flow-through system of the same influx nitrogen and phosphorus concentrations and with different fish (goldfish) densities were conducted from Aug., 1993 to Sep., 1994 to investigate the factors influencing the dominance of blue-green algae in summer. In general, blue-green algae predominated in fish ponds, in contrast to green algae in fishless ponds. Blue-green algae started to flourish after the latter half of August, when the PO₄-P concentrations decreased to less than 10 μg·l^-1. The difference in dominated phytoplankton between fish and fishless ponds could be explained by the reduction of total phosphorus and subsequently the depletion of PO₄-P in pond water due to the feces of fish and their growth, the condition of which is advantageous for blue-green algae than others.

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The relationship between salinity and the algal growth was investigated by algal assay procedure and by field survey in Lake Koyama-ike, Lake Togo-ike and Nakaumi which are located in Tottori prefecture.
From the field investigation the following results were obtained. Water bloom of Microcystis spp. and Anabaena spp. were observed at less than 1200mg·l^-1 of Cl^- concentration and at more than 23°C and 18°C of water temperature, respectively. Red tide of Prorocentrum minimum occured at levels higher than 3500mg·l^-1 of Cl^- concentration and was observed between 5°C and 27°C.
From the flask experiment significant negative correlation was observed between Microcystis aeruginosa or Anabaena affinis growth and Cl^- concentration. M. aeruginosa growth was hindered at levels above 2300mg·l^-1 of Cl^- concentration and Anabaena affinis growth at levels above 2700mg·l^-1.
The yields for both species were halved at 1500mg·l^-1 of Cl^- concentration. A good positive correlation was observed between growth of both species and water temperature. Positive correlation was observed between P. minimum growth and Cl^- concentration.
It seemed that Cl^- concentration and water temperature were very important factors to controlling the algal succession. There is a posibility that water bloom and red tide are hindered by controlling the Cl^- concentration of brackish lakes.

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Concentrations of Sb in the commercially bottled drinking water were determined by ICP-MS with liner calibration method. Concentration of Sb of the mineral water samples (10 samples) and the natural mineral water samples (24 samples) were higher than the natural water samples (21 samples). The mineral water of No. 13 was 4.40 ng·ml^-1 of Sb (the maximum), and the minimum concentration was under detection limit.

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Sapropel is natural aqueous lake-deposit and covers a great variety of bottom lacustrine deposit which contains not less than 15% of organic substances in the dry residue. One of the organic substances is a humic acid. The mineral compounds of sapropel in lakes participate in biological process, and transform during oxidizing and reductive reactions.
Basic characteristics of humic acid extracted from sapropel (Belarussian) and peats (Indonesian tropical peat and Canadian peat moss) were compared. Humic acid extracted from sapropel contains much aromatics in the structure and high ash content. As for the functional group, humic acid from sapropel has higher quantity of phenolic hydroxyl group. Sapropel also contains high quantity of K,P and N and is the most prospective for using as fertilizer for poor land. As the results of greening test at UAE desert, sapropel showed a high performance as a fertilizer than blank.
Authors are planning to evaluate a lake-deposit in Japan with sapropel and to study the possibility of using it as a fertilizer.

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