A virus concentration method was developed utilizing the electrostatic interaction among viruses, multivalent cations and membranes. A negatively charged membrane was used to adsorb viruses from water samples through which diluted sulfuric acid (pH3.0-4.8) was then passed to remove cations from the membrane, followed by the elution of viruses with alkaline solution (pH10.5-12) or with beef extract solution (pH9.5). F-specific RNA phage Qβ and poliovirus type I were used as model viruses and pure water, tap water and artificial seawater were used as samples. The method using a negatively charged membrane with acid rinse followed by alkaline elution showed the highest recovery yields among those tested for polioviruses including the 1MDS positively charged membrane, especially when applied to seawater. This method also has a potential advantage over conventional methods of using inorganic eluant such that there will be no inhibition of the subsequent virus detection by PCR.

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Using milk casein and several kinds of surfactants as chemical agents, removal of suspended solids by coagulation and foam separation with dispersed air was examined. Casein functioned both as a collector and a frother, and coagulating flocs were almost perfectly recovered in foam generated from the liquid. Although oleic acid of anionic surfactant functioned as a collector, the removal efficiency of suspended solids was lower than that of casein. In contrast, cationic, amphoteric, and nonionic surfactants did not function act as collectors. It was clarified that casein had a much greater capacity for producing the hydrophobic interface of flocs than the surfactants used. However, all of the surfactants could also be utilized as frothers for recovering the hydrophobic flocs with casein.
For municipal wastewater treatment, a very high removal efficiency was obtained with a small amount of casein (3mg·l^-1), because detergent contained in the wastewater functioned as a frother. In this method using casein, detergent is one of the object substances in wastewater. It is utilized as a foaming agent and is removed with foam.

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Since most environmental pollutants are thought to finally accumulate in the ocean, it is important to develop a quick and convenient assay system for seawater pollution. In this study, we tested the possibility of using flagellar regeneration in a marine unicellular organism, Dunaliella sp., as an endpoint of bioassay. Dunaliella sp. has two flagella of equal length and swims by beating its flagella. When the flagella are amputated by mechanical treatment, they rapidly regenerate to their original lengths in 6-8 hr. We examined the effects of five pollutants {Cu²⁺, Cd²⁺, linear alkyl benzene sulfonate (LAS), 4-nonylphenol (NP), and bisphenol A (BPA)} on flagellar regeneration. Each chemical exhibited a characteristic inhibition pattern, with the inhibitory effect being stronger in the order of NP>Cu²⁺>LAS>BPA>Cd²⁺. The EC50 value of Cu²⁺ was 4-8 times lower than the effluent standard value in Japan. Flagellar regeneration occurred normally in 20-100% artificial seawater, showing that this endpoint can be used even in brackish water. We therefore collected coastal seawater samples in Toyama Bay and examined their effects on flagellar regeneration. Results showed that the seawater samples collected from some fishing ports and a coastal area inhibited flagellar regeneration, and flagella regrew only to 77-87% of the control length. Thus, the flagellar regeneration assay using Dunaliella sp. appears sensitive and can be a useful method for assessing seawater pollution.

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Methyl-tert-butyl ether (MTBE) has been used as an octane enhancer of automobile gasoline since the late 1970s' in the United States. MTBE has also been added to most high-octane gasoline in Japan. Since ground water is easily contaminated by MTBE due to gasoline leakage from underground tanks, MTBE may affect human health via drinking water. In this article, we have collected data concerning MTBE toxicity and information on MTBE risk assessment. MTBE induced hepatic and renal toxicity in rodents. The no observed adverse effect levels (NOAELs) of non-cancer endpoints for continuous long-term exposure were considered to be 259 mg·m^-3 for inhalation route and 100 mg·kg^-1·day^-1 for oral route. High dose MTBE exposure caused certain tumors (Leydig cell tumor, lymphoma and/or leukemia, renal cell tumor, hepatocellular adenoma) in rodents. However, there is some controversy regarding extrapolation of the rodents' carcinogenic effects by MTBE to humans. This issue has not yet been clearly resolved. The US EPA Drinking Water Advisory recommended a tolerable contamination range of 20 to 40 μg·l^-1 or below in drinking water based on the safety evaluation and organoleptic properties, and analyzed the margin of exposure (MOE) for the general population. For more accurate risk assessment of MTBE, it is necessary to conduct exposure surveys more widely and to examine the mechanism of carcinogenic effects.

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