Predicting Algal Stimulatory Properties of Wastewater

The growth response of the green alga, Selenastrum capricornutum to varying additions of either sewage or reconstituted water containing equivalent levels of inorganic nitrogen and phosphorus, was compared to algal growth levels calculated from the inorganic nutrient concentrations of these additions using the algal yield factor of the test alga. The additions resulted in a linear increase in algal growth with percent of sewage or chemical equivalent solution addition which was in close agreement to the values predicted from the total soluble inorganic nitrogen concentration in the algal cultures alone. Thus, the Algal Assay: Bottle Test (AA:BT) did not permit sufficient organic mineralization during incubation, owing to the exclusion of heterotrophic bacteria and protozoa by the test procedure. This occurrence could result in an underestimation by the AA:BT of the algal growth potential occurring from the entry of a wastewater containing inorganic and organic nitrogen and phosphorus compounds into the aquatic environment.