The removal efficiency of nutrient salts from a reservoir by water hyacinth cultivation was studied based on kinetic models of growth and phosphate uptake. Specific uptake rate of phosphate as a function of the phosphorus content in water hyacinth could be expressed by kinetic model originated from Michaelis-Menten equation.
Simulation results from the proposed kinetic model agreed approximately with the experimental data of growth and phosphate concentration in the effluent from a test culture.
Computer simulation study based on the models suggested that an evident decrease of phosphorus concentration in the reservoir might be possible under a natural environment and that almost all the area of the reservoir would be covered with water hyacinth. The removal efficiency of phosphorus and nitrogen in the case of periodical harvest of water hyacinth was less compared with that of without harvesting the crop. However, since the phosphorus concentration in the reservoir could decrease up to 80-90% of the initial value, it was concluded that a high efficiency of phosphorus removal might be achieved by means of periodical harvest of the water hyacinth biomass.

View full abstract

The pore-water quality in river bottom sediments and water quality are compared and evaluated by gel-chromatography tecnic. In water area polluted for a short time, easily bio-degradable substances exist in both of water and bottom sediments. And, soluble high molecular metabolic substances exist only in sludge, and can be removed by coagulation with PAC. On the other hand, in water area polluted for a long period of time, water has the same pattern of gel-chromatography as that of bottom sediments. And the effects of bottom sediments on water quality are confirmed.

View full abstract

Degradation of three kinds of crude oils such as Arabian light, Berni and Murban crude oil by a pure bacterial strain, Caulobacter sp., and by mixed culture integrated from the sea water sampled at Kawasaki Harbor was studied experimentally in the enriched seawater (ESW) medium.
The degradation of oils were determined in total residual oil and in four fractions of saturated, aromatics, asphaltene and column residue by use of column chromatography.
The saturated fraction was most biodegradable and the aromatics followed for all three crude oils in both pure and mixed cultures. The asphaltene and the column residue were not degraded apparently by microorganisms in 30 days incubation. Crude oils in pure culture were degraded from 30 to 36 percent and 45 to 55 percent in mixed culture. Activities of oil degradation were higher in mixed culture. Average degradation rates of crude oil for the duration of rapid disappearance of oil were calculated to be in a range from 4.92 to 5.83 mg-oil l^-1h^-1 for pure culture and from 15.1 to 19.4 mg-oil l^-1h^-1 for mixed culture. Relative degradation of n-paraffin of different carbon numbers in saturated fraction was similar in both cultures.

View full abstract

[in Japanese]

View full abstract