EFFECT OF GLUCOSE LOADING ON THE GROWTH-BEHAVIOR OF CHLORELLA-VULGARIS AND HETEROTROPHIC BACTERIA IN MIXED CULTURE

The effect of glucose concentration on the growth of Chlorella vulgari s and heterotrophic bacteria in mixed culture was studied. Granular gl ucose was fed daily as a source of organic carbon to provide an input concentration ranging from 25-700 mg/l. Growth rates of heterotrophic bacteria and algae increased with glucose loading rate but excessive l oading rates were detrimental to the survival of the algae and bacteri a. The maximum specific growth rates for the algae and bacteria were 1 .58 and 1.70 d(-1), respectively. However, the saturation constants we re significantly different with values of 27 and 174 mg/l for bacteria and algae, respectively. Under anaerobic conditions, bacterial densit y and algae growth were significantly affected by accumulation of vola tile fatty acids (VFA). Although in low glucose loaded reactors, pH re ached as high as 10.6, no significant effect of pH was observed on the survival of Chlorella vulgaris and heterotrophic bacteria. Inorganic carbon production increased with increasing glucose loading rate. When volatile fatty acids accumulated in anaerobic reactors, pH dropped re sulting in a shift of equilibrium between H2CO3, HCO3- and CO32- in fa vor of H2CO3 production, most of which was released as CO2(g) to the a tmosphere.