Leftovers of feeds, which were fed to waterfowls by visitors to the park around a pond, are one of the causes of water pollution and eutrophication in the pond. We investigated why visitors have wanted to feed waterfowls. And, we estimated an influence of feeds residue on water quality of the pond. Most of the visitors, who are under the forty years old, thought, “I want to contact with waterfowls.” “I think feeding is good for children as environmental education.” and they wanted to feed waterfowls. These visitors occupied about 40% of the whole visitors. About 36% of COD existing in the pond originated from the leftovers of feeds. Then, we considered a new plan that the feeding action will be compatible with water quality preservation. Based on our simulation analysis, we explained that a feeding pond construction is the best plan for that.

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To clarify the role of waterfront vegetation for Chironomid midges and make it useful for control countermeasures, an investigation of the number of chironomid midges resting on each form of vegetation and how they use Phragmites australis was conducted on massively breeding Chironomus plumosus and Eifeldia dissidens. As a result, significant differences were observed in the number of resting chironomid midges according to the type of chironomid and vegetation. Chironomid midges rested on Melilotus alba with the highest density. As for C. plumosus, many chironomid midges tended to rest on plants which had many leaves per unit stem length. About 70% of chironomid midges which flew to P. australis stuck to the leaves. The difference in numbers was not significant for either side of the leaves. In light of the above, the fact that such varied forms of vegetation exist in the shoreline area would mean that the chironomid midges may avail themselves of all kinds of resting places of the kind. In addition, it was thought that were a larger vegetation area to be secured along a lake waterfront, these midges could effectively provide a buffer zone between human living space and their own habitats.

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Adsorption characteristics of Biological Activated Carbon (BAC) operated for 5 years and 3.5 years in a pilot plant were evaluated for simazine. The performances of both BACs on natural organic matter (NOM) removal were completely the same. Both BACs removed NOM with less than 500 daltons of the apparent molecular weight fraction by biodegradation, however, they can not remove NOM by adsorption at all. GAC saturated with NOM in a laboratory for short-term showed larger adsorption capacity for simazine than both BACs from the pilot plant. The BAC operated for 5 years showed smaller adsorption capacity for simazine than the BAC operated for 3.5 years, suggesting BAC is gradually saturating with simazine after saturation with NOM, even after 5 years operation. NOM with less than 500 daltons competed with simazine for adsorption site on BAC, however, NOM with more than 3,000 daltons did not affect on simazine adsorption on BAC which is long-term operated.

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Characteristics of pollutant loads and water quality, and the relation between water quality of the influent and the effluent were investigated for domestic wastewater treatment facilities, which were designed for 51 persons or more and have long inflow pipeline. It was found that average values of pollutant loads were 243l for water quantity, 37.9g for BOD, 8.1g for T-N, and 1.0g for T-P per capita per day, and non-excess probability 75% values of pollutant loads were 286l for water quantity, 44.2g for BOD, 9.1g for T-N, and 1.1g for T-P per capita per day. By the result of principal component analysis, the first component mainly characterized the total water quality, while the second component described the dissolved matters. It was also found that chlorine ion compensation was an effective method for analyzing water quality characteristics of domestic wastewater. On the other hand, the ratios of BOD to TOC and D-BOD to D-TOC in influent were both about 1.5, while the ratios of C-BOD to TOC and D-BOD to D-TOC in effluent were 0.61 and 0.34 respectively. These results indicated that there was a given quantity of organic matters, which dissolved in the effluent and were not detected in BOD analysis. When the effluent T-N was under 20mg · l^-1, the effluent D-COD and D-TOC were under 10mg · l^-1. It was suggested that D-COD and D-TOC may be utilized as organic carbon source in nitrogen removing.

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