A filamentous bacterium capable of utilizing 4-methylpyridine and 4-ethylpyridine as the sole source of carbon, nitrogen and energy was isolated from sludge. The organism, designated as strain M43, clustered most closely with members of the genus Pseudonocardia by 16S rRNA gene sequence analysis. During the degradation of 4-methylpyridine and 4-ethylpyridine, c. 60% of nitrogen in the pyridine ring was released as ammonia. Metabolite analyses showed that 2-hydroxy-4-methylpyridine and 2-hydroxy-4-ethylpyridine were transiently accumulated during the degradation of 4-methylpyridine and 4-ethylpyridine, respectively. Strain M43 was also able to degrade pyridine, 3,4-dimethylpyridine, 4-carboxypyridine and 2-hydroxy-4-methylpyridine. The results indicate that degradation of 4-methylpyridine and 4-ethylpyridine by strain M43 proceeded via initial hydroxylation.

Effect of the effluent of the sewage and wastewater plants on the algal growth was investigated from the 19 plants located in the Nakdong river basin. Most of the samples showed high values of the algal growth potential (AGP) when they were mixed with natural river water at 20% of final concentration. At 20% of the mixing ratio, the mixed effluents of sewage and wastewater showed 3.5 and 1.8 times higher AGP than those of the natural river water. The higher AGP values are attributable to the high contents of phosphorus and ammonium in the effluent. The mixing ratio of effluents of the discharge/river flow was highest in the Kumho River (42.8%) followed by the middle of Nakdong River (22.7%), Kam Stream (13.9%), Byungsung Stream (13.3%), Yangsan Stream (7.9%), and Young River (5.4%). Comparison of the trophic state of the effluents with natural river water indicated that the effluents showed higher trophic values than natural water. Concentrations of total phosphorus, total nitrogen and conductivity in the effluents were 12.3, 4.9 and 5.3 times higher than the those found in natural river water respectively. The AGP values were highly related with the trophicity of the water especially on the concentrations of phosphate and ammonium. Toxicities of the treated sewage water, wastewater and livestock waste water tested by the luminescent bacteria, Vibrio fischerii were generally low.

A seasonal variation of phytoplankton community in the Naktong River was studied in seven sampling stations at monthly intervals from April 2000 to March 2001. Environmental factors such as conductivity, total phosphorus, total nitrogen and BOD were much higher at a lower reaches than the upper reaches. Especially, they rapidly increased at the st. 4 located near the discharge of the Kumho River. Total 239 taxa observed in the study were classified into 201 species, 22 varieties, 2 forma, 1 morphotype and 13 unidentified species belonging to 102 genera, 39 families, 17 orders and 8 classes. The phytoplankton standing crops were recorded a maximum of 33,389 cells • ml -1 at the st. 7 in June and a minimum of 139 cells • ml -1 at the st. 1 in September. The correlations between averages of the phytoplankton standing crops and some of environmental factors were investigated at each sampling station. The coefficients of correlation between average of the phytoplankton standing crops and BOD, T-N and T-P were 0.61, 0.45 and 0.47, respectively. In general the dominant species were Achnanthes minutissima Kütz, Nitzschia fonticola Grun., Navicula cryptotenella Lange-B in the upper reaches, Microcystis aeruginosa (Kütz.) Kütz. and Stephanodiscus hantzschii Grun. in the lower reaches.

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