Abstract
A new process is proposed for carbon and nitrogen removal from wastewater. The effects of pH and various concentrations of butyric acid and NH 4 +N on the aerobic growth of Candida utilis growth at 30°C were determined in batch cultures. Butyric acid stimulated growth at low concentrations (lower than 5 g litre −1) but was inhibitory at higher concentrations. Growth was also inhibited by free ammonia at pHs greater than 8·0 but concentrations of this inhibitor decreased in the reactor as a result of stripping. Limiting conditions for growth were 0·81 g litre −1 of undissociated butyric acid and 0·08 g litre −1 of ammonium-nitrogen. The growth rate was optimal at pH 7·0 while maximal removal of nitrogen was obtained at pH 7·5. A general expression for specific growth rate was developed, tested and validated to model C. utilis growth with inhibition by NH 3 and undissociated butyric acid.
Published Version
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