Abstract
A countermeasure of preventing the eutrophication of lakes and marshes is to use filamentous algae to remove dissolved phosphorus and nitrogen from the waters of rivers flowing into them. In order to establish a procedure for harvesting filamentous algae growing in artificial waterways and a effective use of the harvested algae, it is necessary to clarify the quantity which can be harvested.
In the waterways, the quantity of algae separated from the substratum which are discharged outside the waterway or which accumulate in the interior of the waterways varies for each harvest. Cosequently, it is possible to predict the harvesting yield of algae which is separated from the substratum as the function of the phosphorus content, phosphorus absorbing ability, and the constant of non-harvesting algae.
The results of calculations based on field experiments with filamentous algae have confirmed that the harvesting yield is dependent upon the water temperature, concentration of nutrient in the raw water, and the stream regime. Typical harvesting yield values were obtained. When we treated raw water of dissolved orthophosphate concentration of 30μg·l-1 at water temperature of 20°C using a gentle-sloped waterway, we found that the harvesting yield was roughly 20g dry weight·m-2·d-1.
