Bioassay techniques for testing treated waste water (sewage effluent) and toxic chemicals in seawater by monitoring the growth of seaweed were reviewed in this paper. Waste waters have been tested by seaweeds were classified into indusrial waste water, sewage effluent, night-soil effluent, antifouling chemicals in sea-water and other toxic chemicals in seawater. Porphyra tenera or yezoensis (nori) in Japan and Macrocystis pyrifera (giant kelp) have mostly been used for biological testing in past researches. P. tenera or yezoensis and M. pyrifera were chosen for toxicity bioassays of treated sewage effluent due to their biological and socio-economic effectiveness and significances. Bioassay techniques such as the life stages of specimens and test periods required, methods of detecting adverse effects of effluent on specimens, culture methods, culture conditions, culture media and effluent sampling times were described. Chemical substances which promote or hinder the growth of seaweeds are contained in the treated sewage effluent and chemical substances and their concentrations change daily and weekly. Lower salinity intensify the adverse effects of effluent on growth of seaweeds. Therfore, variables such as effluent concentration, salinity of culture media and dayly and weekly changes of effluent must taken into account. It was clarified by the proposed bioassay techniques that the strongest toxic substance on the growth of P. yezoensis was monochloramine resulting from chlorinated sewage effluent. P. yezoensis is considered to be the appropriate seaweed for toxicity bioassay of treated sewage effluent for the biological and socio-economic effectiveness and significances in Japan.

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Recently reported virus contamination in natural waters is considered to be closely dependent upon insufficient virus removal in the sewage treatment process. Therefore, it is necessary to clarify the behavior of viruses in the treatment process.
This research was undertaken to elucidate the factors effecting virus behavior in an aeration tank in the activated sludge process. This process is at present the most popular biological sewage treatment method. The effects of MLSS concentration, temperature and pH on virus reduction were investigated in batch experiments using a vaccine strain of attenuated poliovirus type 1 (LSc, 2ab) as a model virus. The infectivity of virus was determined by the plaque assay using BGM cells.
The results indicated that the virus infectivity in a mixed liquor of activated sludge decreased exponentially with time. Regardless of MLSS concentration, temperature and pH, the time course of virus infectivity reduction could be expressed as two consecutive stages. The first stage decreased more rapidly than the second one while both were characterized by first-order kinetics. The reduction of virus infectivity was found to be proportional to MLSS concentration and effective for the condition of low pH and high temperature in the aeration tank.

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Sorption and desorption of trichloroethylene (TCE) on various soils were investigated. The sorption and desorption of TCE on soils could be described by the Freundlich equation. The sorption and desorption Freundlich parameter, (n) were nearly equal to unity and linear isotherms were observed at low concentration levels (ex. Andosol : < about 20 μg·l^-1). The equilibrium of sorption and the first equilibrium of desorption of TCE were achieved in one day. The sorption and desorption of TCE was strongly dependent on the organic carbon content in soils. About one tenth of adsorbed TCE on soils was not desorbed by repeats of water extracts. The sorption coefficient (K_s) was less than the desorption coefficient (K_d).

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Micro-structure in sediments of a tidal river, which is composed of microsites of various ranges of Eh level, is experimentally investigated. At first, the cytochrome oxidase activity in the sediments is measured to study the distribution of aerobic microorganisms. Sediments with a high ignition loss are high in the activity and dense in aerobic microsites down to 5mm from the water-sediment interface. On the other hand, those with a low ignition loss are low in the activity and rather disperse in aerobic microsites down to 4cm from the interface. Secondly, the reduction of tetrazolium salts in the sediments is examined to obtain distributions of reduced microsites. The results indicate that they exist patchy in the oxic and anoxic parts of the sediments and their spacial ratio increases with depth. Finally, Eh in the sediments is measured with handmade micro-electrodes with 17μm in tip diameter and 500μm in length, whose dimension is the same size or smaller than the average size of the microsites. The values of Eh measured in vertical and horizontal planes of the sediments range from positive to negative values.

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The long-term and seasonal variations of anionic surfactants in rivers of Kinki Region were statistically evaluated by using MBAS (methylene blue active substances) monitoring data during 1972-1988.
High concentrations over 1 mg·l^-1 as the average for the observation period were found in 18% of the 440 monitoring stations, and 30% of the total stations indicated significant long-term variations of MBAS concentration which was charaterized by the decrease at high concentration points. The relation between the ratio of the population served by public sewerage and MBAS concentration suggests that the diffusion above 80% is necessary in decreasing to MBAS level below 0.5 mg·l^-1 in urban rivers.
In many cases, MBAS correlated positively with BOD and negatively with water temperature at different stations and in different prefectures, and the contributions over 0.5 were obtained in multiple regression analysis with MBAS as criterion variable and BOD and water temperature as explanatory variables. These suggest that the two paramerers explain predominantly the variations of MBAS concentration in river waters.

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