EFFECT OF PHOSPHORUS ADDITION ON NUTRIENT REMOVAL FROM WASTE-WATER WITH THE CYANOBACTERIUM PHORMIDIUM-BOHNERI

The growth and inorganic nutrient removal capacity of the cyanobacteri um Phormidium bohneri on domestic wastewater were investigated in outd oor 24-l triangular bioreactors with or without the presence of added inorganic phosphate. While the addition of monopotassium phosphate did result in lap to 56% more biomass production and had an influence on the kinetics of the removal of inorganic nutrients, it did not signifi cantly affect the total rime taken for complete removal of these nutri ents. In all cases, nitrogen (ammonium and nitrate) and phosphate were removed after 50 and 75 h of growth, respectively. Biomass pro ductiv ities of 23-57 mg d.m. l(-1) day, combined with rates of ammonium and phosphate removal lip to 20 mg l(-1) day(-1) indicated that P. bohneri has a good potential for. wastewater treatment. In the presence of ad ded phosphate, after 40 h of growth, rates of phosphate removal became erratic, with peaks of phosphate appearing at the beginning of the da ylight. These results were interpreted in relation to the complex dyna mic equilibrium existing between different forms of phosphate. (C) 199 7 Elsevier Science Ltd.