Semicontinuous Outdoor Cultivation of Scenedesmus acutus in Waste Water

The algae were cultivated in an outdoor cultivation unit in waste water from sewage treatment plant processing city sewage and largescale hoggery effluent. The cultivation area (2m²) had a slant of 3% and the suspension layer thickness was about 5 cm. The total suspension volume in the cultivation device was 150 I. Mass balance served us for derivation of formulas for the average rate of algal biomass production and for the extent of nutrient removal from waste water. Experiments showed a considerable effect of dilution rate on individual parameters in these formulas. The removal of nitrogen and phosphorus is optimal at a dilution rate of 0.3 day^?1 whereas optimum biomass production lies at about 0.1 day^?1. The nitrogen and phosphorus yield coefficient Y (g biomass/g element) are practically identical, both of them depending on dilution rate. The effect of the dilution rate on other characteristics of the effluent water has not yet been unambiguously proved. The results are shown of bacteriological and mycological examinations, in addition, of the chemical analysis of resulting algal biomass.