The seasonal and long-term changes of MBAS in rivers and coastal waters in Hyogo Pref. were statistically analyzed with the monitoring data in the last 15 years.
In the river water, high concentrations (1 mg·l^-1≤) of MBAS were observed at least once in 58% of overall monitoring stations. Many smaller rivers in Hanshin District, where the population and the industry were intense, were always polluted with anionic surfactants. However, gradual decreases in MBAS were observed by the degree greater than those of BOD in over 70% of the stations during the monitoring period. As to the seasonal changes, MBAS concentrations were higher in the cold season (Jan.-Mar. and Oct.-Dec.) and lower in the warm season (Apr.-Sep.) in 60% of the stations.
The causes of the long-term change and the seasonal change are presumed to be the diffusion of sewerage system in various areas and the active biodegradation of MBAS under higher water temperature, respectively.
In the coastal waters, long-term changes of MBAS were similar to those of the river water, while seasonal changes observed were different.

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Biodegradation of linear alkylbenzensulfonate (LAS) in Tama River sediment was studied using two model test systems.
LAS consentration in the sediment decreased gradually at initial stage of the experiment, followed by linearly decreasing. Michaelis-Menten model was applied to the linear portion of the biodegradation curve and the maximum rates, V_max, for the degradation of total LAS and LAS constituents were estimated.
V_max values of total LAS were 0.689 and 0.792 mg·kg^-1·d^-1 for two model tests. V_max of LAS constituent became greater as the number of alkyl carbon in LAS decreased.

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Laboratory scale reactors were used to investigate the phosphorus behavior in microorganisms responsible for the operational conditions in performance in order to develop the process for the removal as well as the enriched phosphorus recovery from wastewater by using the immobilized biofilm under cyclic anaerobic and aerobic conditions. Operational parameters varied include the ratios of anaerobic and aerobic periods, operating and feeding patterns, and consideration of organic carbon and phosphorus loading conditions. To achive the proposed process successfully, the results obtained from the experiments are as follows : feed is required to supply continuously at the aerobic period and instantaneously at the anaerobic period. Organic carbon loading at the aerobic stages is required of a low loading. The amounts of phosphorus uptake under aerobic conditions are strongly correlated to those of its release under anaerobic conditions.

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A fluidized bed reactor with Amberlite IRA-938 as a support medium was employed for accomplishing the high efficient biological nitrification. Effects of the hydraulic retention time (HRT) and the influent glucose concentration on the efficiency of the biological nitrification were investigated.
More than 90% of influent NH₄-N was nitrified even at a HRT of 0.5h. The maximum nitrification rate in this study was 1300mg-N·l^-1·d^-1, which was much greater than that obtained in activated sludge process. This high nitrification rate was attributed to the macroporus characteristics of Amberlite because Amberlite could maintain a large number of nitrifying bacteria in its inside. Results of batch experiments on the nitrification rate indicated that the oxidation of NH₄-N proceeded in the outer region of the Amberlite and that of NO₂-N did in the inner region.
In both experiments with influent glucose concentrations of 10mg·l^-1 at a HRT of 0.5h and 20mg·l^-1 at a HRT of 2h, more than 90% of influent NH₄-N was nitrified. Therefore, this type of fluidized bed reactor could be applied to the advanced treatment of sewage.

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