The results showed that photosynthetic and respiration rates observed in the algal biofilms were influenced by biofilm composition, culturing conditions, orientation to the light, and nutrient availability. Nutrient removal capacity was highest during the exponential growth phase of the biofilm. A slight increase in lipid production was observed as a result of nitrogen stress and a combination of nitrogen stress with bicarbonate addition. Presence of bacteria positively influenced microalgae growth in the mixed cultures but the reverse was not true.