Long‐term effluent variability from an anaerobic fixed film reactor

Abstract

A laboratory anaerobic fixed film bioreactor was operated continuously for over a year at constant sucrose feed concentration and constant operating conditions. A nonvarying effluent in terms of chemical oxygen demand (COD) concentrations (soluble and total) and concentrations of volatile fatty acids (acetic and propionic) was difficult to obtain. Effluent variability was examined by frequency distribution and time series analysis. The data showed a tendency to the log‐normal distribution. Effluent soluble and total COD concentrations demonstrated low frequency variability and auto correlations at different time lags. Fatty acids showed cyclic trends and auto correlations at about the same lag. Variations in effluent quality are attributable to the basic nature of the anaerobic fixed film process.