Utilization of cyanobacteria in photobioreactors for orthophosphate removal from water

The effectiveness of photosynthetic free-living and polyurethane foam (PU) immobilized Anabaena variabilis cells for removal of orthophosphate (P) fro m water in batch cultures and in a photobioreactor was studied. Immobilizat ion in PU foams was found to have a positive effect on P uptake by cyanobac teria in batch cultures. The efficiency of P uptake by immobilized cells wa s higher than by free-living cells. A laboratory scale photobioreactor was constructed for removal of P from water by the immobilized cyanobacteria. T he photobioreactor was designed so that the growth medium (water) from a re servoir was pumped through a photobioreactor column with immobilized cyanob acteria and back to the reservoir. This created a closed system in which it was possible to measure P uptake. No leakage of cells into the photobiorea ctor medium reservoir was observed during the operation. The immobilized ce lls incorporated into a photobioreactor column removed P continuously for a bout 15 d. No measurable uptake was demonstrated after this period. Orthoph osphate uptake efficiency of 88-92% was achieved by the photobioreactor.