Photosynthetic purification of the liquid phase of animal slurry
Abstract A strain of Chlorella vulgaris has been selected from amongst 18 species of freshwater algae which were screened for their ability to grow in, and remove phosphorus from, the liquid phase of slurry. In a laboratory batch culture system phosphorus is first solubilised by the developing endogenous bacterial community, then accumulated by the algal cells. Little of the nitrogen lost from the system can be attributed to algal assimilation. The algae produce sufficient oxygen to oxidise the effluent in the absence of supplementary aeration but an aeration treatment prior to inoculation is required to raise the redox potential to 330 mV and minimise the lag phase of algal growth. The harvested algal cells contain 42% true protein and substantial amounts of phosphorus, leaving a final effluent with a BOD = 4 mg/l, SS = 130 mg/l and total phosphorus concentration = 2·5 mg/l.