This paper proposes cultivation of algae in urban wastewaters as a sustainable approach for removing the nutrients from the wastewaters and generating energy from the biomass. The theoretical rationale of this proposal is that, the algal systems can produce nearly double the biomass per unit nutrient intake than bacterial systems and can generate nearly 20% more net energy. Preliminary experimental results are presented to demonstrate that a thermotolerant and acidophilic algal strain evaluated in this study-Galdieria sulphuraria, can grow well in primary settled urban wastewaters and can reduce nutrient levels to regulatory discharge levels at reasonable rates. Nutrient removal rates found in this study (4.70 to 5.0 mg L-1 d-1 of nitrogen and 1.5 to 1.7 mg L-1 d-1 of phosphate) are comparable to those by traditional methods.
1. Attention is drawn to the remarkable dissimilarity between the cacao and the grapefruit tree in their nutrient requirements, indicating that grapefruit is calcicolous in physiological habit. This conclusion is mainly based on a consideration of the results of chemical analysis of representative leaf material produced by trees grown on soil of known chemical and physical characteristics, under the same climatic conditions in Trinidad.2. The nutrient relationships that obtain between the cacao and the grapefruit tree respectively and the soil in which they are growing have been gauged by means of chemical analysis of representative leaf material.3. For this purpose, leaf material was obtained from trees growing on the differently manured plots of two large-scale field experiments in Trinidad.
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