Distribution of sulfate-reducing bacteria (SRB) along with the depth, and correlation between sulfur and heavy metal in the layer of an open-dumping landfill site (95 m depth), Nanjido, Seoul, Korea, were investigated. It was found that SRB were widely distributed in all layers of the Nanjido landfill site with range 10³ to 10⁶ MPN/ml. Sulfur values were highly correlated with heavy metals concentrations of the landfill site in accordance with depth. Number of SRB, quantities of sulfur and total metals in suspended solids (SS), were 10⁶-10⁹ MPN/ml, 2.71% and 3.15%, respectively. Moreover, values of those in sediment from the bottom of leachate catchment basin were recorded as 10⁵-10⁸MPN/ml, 2.60% and 3.29%, respectively. Therefore, it was assumed that heavy metals move as SS (floc) form from upper layer to the bottom. From these results it is deducible that formation of metal sulfide by SRB in presence of higher sulfur, may play an important role in insolubilization of heavy metals in Nanjido landfill site.

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We developed an effective biological treatment process for ammonia-rich inorganic industrial wastewater such as wastewater discharged from demineralizer regenerating process in the power plant. In continuous nitrification experiment with completely mixed three-phase fluidized bed reactor filled with cement ball as carriers, 50 μm thick biofilms composed of nitrifying bacteria were obtained. In addition, nitrification rate was successfully improved mainly due to acclimation of nitrifying bacteria to higher loading by gradual reduction of hydraulic retention time. Final nitrification rate reached 0.33 kg-N/m³/day. In denitrification batch test, the optimum amount of methanol as carbon source for denitrification process was determined to be the C/N ratio of 1.7. Total nitrogen removal performances in the aerobic-anaerobic configuration and the anaerobic-aerobic circulation configuration were compared. As a result, the aerobic-anaerobic configuration showed better nitrogen removal performance, which achieved the effluent T-N below 10g/m³. Finally, 13 kinds of nitrifying bacterial colonies were isolated from the aerobic reactor of aerobic-anaerobic configuration, two of which showed higher nitrification ability.

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Astep-feed anoxic-oxic activated sludge process is one of the most practical methods for the up-grading of existing conventional ones to enhance nitrogen removal efficiency, eliminating internal water recirculation and supplement of external carbon source for denitrification. In this study, effect of step-feed ratio on the biological nitrogen removal of the process was investigated by a kinetic model in pilot-scale experiments. The results showed that the optimal step-feed ratio for nitrogen removal depended on water temperature in the tanks. There was little effect of the step-feed ratio on T-N removal at relatively low temperatures around 17°C. As the water temperature became lower, the nitrification efficiency seriously decreased, and then the effect of the step-feed on denitrification would be canceled. On the other hand, the optimal step-feed ratio for T-N removal was around 0.4 at 20 to 30°C. At higher temperatures, denitrification process seemed to be rate limited at the lower step-feed ratios, while the nitrification process would be rate limited at higher step-feed ratios.

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A new reactor equipped with the string-type media twined with yeasts was developed in order to treat kitchen wastewater from restaurants and discharge it into sewerage system. The first treatment facility seeded with the mixture of the isolated mycelial yeasts, was installed at a restaurant in 1995. After three years, the treatment performance of this facility was investigated for a year. The yeast reactor was able to remove more than 90% of BOD and hexane extracts in spite of a large load variation. A part of the twined yeasts with media were separated by periodic excessive aeration and washed out. The separation of the twined yeasts resulted in 55-125mg/l of SS concentrations in the effluent. This yeast process could meet the discharge limits completely with no sludge disposal.

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p-Nitrophenol (PNP) is a toxic compound which enters the environment through various industrial sources. For its biological degradation, cultivation and acclimation of p-Nitrophenol degrading microorganisms is essential. During the initial cultivation of p-Nitrophenol degrading biomass from activated sludge in this study, the mixed liquor suspended solids (MLSS) concentration dropped steadily requiring the need of a second easy-to-degrade carbon source for biomass growth. Five second carbon sources namely glucose, phenol, urea, aniline and yeast extract were examined for their utilization as a co-sutbstrate in p-Nitrophenol degradation. p-Nitrophenol degradation, total organic carbon (TOC) disappearance and biomass growth were investigated. Glucose and yeast extract were found to be suitable co-substrates, however, from the points of view of cost, specific p-Nitrophenol degradation rates and self degradation, glucose was preferred over yeast extract. Thus, use of glucose is recommended as a second carbon source in the acclimation and growth of p-Nitrophenol degrading biomass. A glucose concentration range of 100 to 1000 mg/l can be used depending upon the desired rate of biomass growth.

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The purpose of the paper is to develop new synthetic indexes of water qualities of rivers and to clear their significance in the evaluation of water pollution of Japanese rivers. The synthetic indexes were produced from their data of physical and chemical water qualities as well as flow-rates, including also the estimation of the Saprobic levels from those physical and chemical data. The principal component analysis (PCA) was applied to 119 rivers of class “A”in Japan whose seven years data were selected from 1975 to 1993. The first main component F₁ represents the factor of loading of water pollution. The second one F₂ represents the factor of its level.
Two patterns of river pollution can be found by plotting pairs of F₁ and F₂ values of each river on the graph of the F₁, F₂-axis. Correlation between the synthetic indexes and watershed factors of 33 “A”rivers in Japan was investigated. Each synthetic index, F₁ as well as F₂, can be expressed by multiple regression formula with some watershed factors.
It's concluded that F₁ and F₂ values can be used as the synthetic indexes of water qualities of rivers in Japan in evaluating their water pollution synthetically.

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