In recent years, physiological active substances (e.g., pharmaceuticals) detected in water environments have become an emerging public concern. However, limited study of their occurrence in river water in sewered and unsewered areas exists. In this paper, we describe the occurrence of pharmaceuticals in five rivers whose basins have different wastewater treatment conditions. We found 56 substances (e.g., antifebriles, anti-inflammatory agents, antihypertensives, antibiotics, etc.) in river water. The concentrations of these substances differed according to the basin conditions, that is, a higher concentration was observed in the basins with a lower sewerage ratio. In addition, we conducted an environmental risk assessment of existing pharmaceuticals of high concentration in river water. The MEC/PNEC values of carbamazepine, acetaminophen and triclosan were 0.36, 0.39 and 106, respectively. More information on the effects of pharmaceuticals (e.g., carbamazepine, acetaminophen, triclosan) on aquatic organisms, and data monitoring are necessary.

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The relationship between the formation of river water quality and the land use of river watershed at Lake Kasumigaura (Ls. Nishiura and Kitaura) was investigated in this study using measured in situ data and data calculated using a geographic information system (GIS). NO₃-N concentrations in river water were high, particularly in L. Kitaura watershed. The NO₃-N concentrations increased at a low-water-temperature period and decreased with dilution after rainfall. The relationship between river water quality and land use characteristics in river watershed was examined by principal component analysis. The nitrogen concentrations in river water were correlated with the number of livestock, upland field and forest area in their watershed at ordinary flow. A high correlation was confirmed particularly between the number of pigs and NO₃-N concentration. Paddy field and urban area were correlated with phosphorus, organic matter and particulate matter concentrations. During flood due to rainfall, the nitrogen concentrations in small-scale rivers showed a high correlation with only the number of pigs.

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An experimental study was conducted to establish the control strategy of an anoxic-oxic sequencing batch reactor system (AOSBR) using a specific feature of N₂O generated during the anoxic and oxic phases. Since NH₄⁺-N, NO₂^--N and gaseous N₂O (GN₂O) were found to disappear simultaneously in the oxic phase, the end point of nitrification may be detected from the GN₂O profile. It was suggested that the stagflation of nitrification and denitrification could be detected by abnormal GN₂O emission in the oxic and anoxic phases. Compared with the conventional indexes of AOSBR, GN₂O has several advantages. First, the regulation of GN₂O emission could be conducted directly, and second maintenance is easier than conventional indexes because the GN₂O monitoring system is more durable than the monitoring system for water quality.

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Decolorization using the purification capacity of soil is used as a cheap method in wastewater treatment. The problem of this method is its ease of clogging. The use of pumice soil is expected to induce no clogging since it is granular. In this study, the effect of heated pumice soil on the decolorization of secondary effluent from a swine livestock barn is examined, and the mechanism of decolorization using heated pumice soil is discussed. Furthermore, the improvement of the regeneration effect is examined by adding a thermal regeneration step to the handling of the soil used. As a result, the best decolorization rate is achieved at 300 degrees C, because this is the level at which adsorptive water which hinders to absorb pigments disappears mostly, the noncrystalline quality which induces the absorption of the main mineral ingredient of pumice soil i.e., allophone, is maintained at this temperature. Concerning the regeneration of the soil used, the color degree was successfully reduced below the desired value (100 color degrees); it was improved to 37 color degrees at the maximum by adding a thermal regeneration step at 400 degrees C heating. Moreover, it was clarified that with thermal regeneration, the soil can be repeatedly used for a maximum of 4 times, by which processed water can be pressed down below to the desired value.

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