Effect of acidic deposition caused by the combustion of fossil fuel on surface waters has become significant in the United States and European countries since 1960s. On the other hand, the surface water acidification due to atmospheric pollutants has not yet been observed in Japan. For the long-term prediction of acidic deposition effect in Japan, an appropriate predictive method is neccessary. Comparison of acidified rivers and lakes in the United States and Europe, and surface waters in Japan, shows that the pH level of precipitation is higher and the acid neutralizing capacity (ANC) of watershed soil is larger in Japan than in these countries. Therefore, the acidic deposition effect in Japan should be predicted using a numerical model which takes into account the ANC of the watershed reasonably. From a viewpoint of reliability and applicability, four previous models: ETD, MAGIC, Birkenes and ILWAS are noted. However, these models may need verifications or modifications on their runoff components and mineral weathering submodels in their applications to Japanese watersheds, where geomorphological and geological conditions are different from those in the United States and Europe.

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The research and development is concerned with shortening the UASB startup period in the case of seeding digested sewage sludge. The method is to make Methanosarcina nuclear of granules and to promote granulation by adding methanol to wastewater of which dominant carbon source is acetic acid.
Methanosarcina forms pellets easily and settles rapidly.
An nuclear affects the granulation more effectively than loading rate, up-flow velocity and so on. It was confirmed that granulation was progressed by the addition of methanol. When the dosage of methanol is 500mg·l^-1, the methanogenic activity of the sludge in the UASB gets 1.4 times higher than that of the sludge without methanol. This means that the addition of methanol contributes to shorten the UASB startup period.
However, were the methanol-sludge load not under 1.5g-methanol.(g-VSS)^-1·d^-1, acetic acid removal capacity of the sludge would regress.

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In order to verify the simultaneous removal of nitrogen, phosphorus, and BOD in domestic wastewater, the experimental fullscale plant test has been developed. The experimental plant consisted of anaerobic-aerobic sequencing batch activated sludge reactor (SBR), a compact sludge thickening equipment and filtration tank. Through one year verification test by leading the wastewater discharged from apartment houses into experimental plant, following results were obtained. The average values of treated water for BOD, COD, SS, T-N and T-P were 5.0, 8.2, 3.8, 7.7 and 0.7mg·l^-1, respectively, and the removal rates of them were 97.9, 91.8, 98.2, 81.0 and 82.5%, respectively. Excellent BOD, nitrogen and phosphorus removal was simultaneously achieved without any addition of carbon source for denitrification and pH conditioner such as NaOH.

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The inhibitory effects of six kinds of aromatic compounds (benzoate, phenol catachol, resorcinol, hydroquinone, phloroglucinol) on the acetotrophic methanogenesis were investigated by batch anaerobic toxicity assays. The relative methanogenic activity remaining after addition of aromatic compounds decreased with an increase in the concentration of all aromatic compounds tested. The concentrations (IC₅₀) of benzoic acid, phenol, catechol, resorcinol, hydroquinone and phloroglucinol resulting in 50% inhibition of methanogenic activity were 49.2, 18.6, 22.7, 27.7, 40.0, and 51.6 mmol·l^-1, respectively. The inhibitory effect caused by aromatic compounds varied with the kind of substituent, as well as the number and position of the substituent in the benzene ring. The toxicity of phenol with OH substituent was greatly higher than that of benzoic acid with COOH substituent. The toxicity of hydroxyl group compounds was found to decrease with increase of the number of OH substituent. For dihydroxy-benzenes, the relative toxicity of isomer decreased in the order of ortho>meta>para. For all the phenolic compounds tested, a good correlationship between their inhibition effect and hydrophobicity was observed, and the logarithm of the octanol/water partition coefficient (log P), an indicator of hydrophobicity, was found to be correlated with the inhibition of methanogenic activity, according to the following eqution : logIC₅₀=-0.283logP+1.68 (n=5, r²=0.953).

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