Changes of water quality indicators caused by algal blooms in the recreational ponds in Osaka city were investigated. The results of investigations showed that all ponds were eutrophic and concentrations of chlorophyll-a closely related to that of total phosphorus (T-P) . It was suggested that T-P concentration controlled the density of algal blooms in all ponds. Appearance of algal blooms in 1997 delayed from that in 1996, probably because the rainy season began later and continued longer than 1996.
In a pond where dense algal blooms was observed, dissolved oxygen in the surface water was supersaturated in the daytime, but whole water became anaerobic at night, because of the oxygen consumption by algal respiration. It was suggested that oxygen consumption by dense populations of algae causes bad influence on the ecosystem when temperature of pond water kept over 24°C all night.

View full abstract

Laboratory-scale experiments on the effectiveness of restoration measures for highly eutrophic ponds have been conducted. In these experiments, we used small or large size tanks in which the bottom sediments were installed. We investigated some restoration measures which were assumed to be effective to treat polluted pond water. And then, we have evaluated the effectiveness of biological filter treatment system and phosphorus removal system to reduce the growth of algae. The major results obtained are as follows;
1) Application of slaked lime on the surface of the sediment as a phosphorus inactivant is effective to depress the phosphorus release flux from the bottom sediment but not effective to reduce external phosphorus loading.
2) The efficiency of the rock or sand filter treatment system to remove the algal bloom in eutrophic ponds is uncertain.
3) Biological filter treatment system using ringlace is very effective to remove the algal bloom but not always effective to give better nutrients removal efficiency.
4) Phosphorus removal systems using contact media such as slaked lime are effective to depress the out-break of algal bloom, but have some problems to treat polluted pond water in which algal bloom had already covered the water surface.

View full abstract

In a treatment of night soil, we measured the sumber of microanimals (protozoa and rotifer) in an activated sludge for ten months, and analyzed of the relation between the result and physical chemistry data (pH, DO, temp, MLSS, ORP, DO), and then the treatment water quality (COD, NH₄-N) by double revolution.
As the result, the formula of double revolution model was carried into the number of microanimals both the physical chemistry data and the treatment water quality.
It was suggested that the treatment water guality was improved positively in view of a biology, by the regulation of physical chemistry data following the formula of double revolution model.

View full abstract

In wastewater treatment by polyurethane foam (PUF) fluidized-bed Bioreactor, it was clarified experi-mentally what responses to stepwise substrate loading for TOC, NH⁺₄-N and NO ^-_x-N concentrations in the effluent are observed. The substrate consumption processes were also simulated numerically by introducing the biochemical reaction models in which the effects of biological predator-prey and symbiosis are taken into consideration.
The simulation results were found to predict fairly well the practical changes with day passage in the TOC, NH ⁺₄-N and NO ^-_x-N concentrations in the effluent. The TOC and NH ^+d-N concentrations show the characteristic peaks and decrease thereafter to go to steady state lower values during about ten days. The NO ^-_x-N concentration increases smoothly after stepwise substrate loading and approaches a steady state value.

View full abstract