Effects of organic loading rate on palm oil mill effluent treatment in an up-flow anaerobic sludge fixed film bioreactor

The effect of OLR provided by hydraulic retention time (HRT) and influent chemical oxygen demand (CODin) on the performance of an up-flow anaerobic sludge fixed film (UASFF) bioreactor treating palm oil mill effluent (POME) was studied. Anaerobic digestion of POME was modeled and analyzed with two variables i.e. HRT and CODin. Experiments were conducted based on a general factorial design and analyzed using response surface methodology (RSM). The region of exploration for digestion of POME was taken as the area enclosed by HRT (1 to 6 days) and CODin (5260 to 34725 mg/L) boundaries. Eight dependent parameters were either directly measured or calculated as response. These parameters were total COD (TCOD) removal, TCOD removal rate,
volatile fatty acids to alkalinity ratio (VFA/Alk.), CO2 fraction in biogas, solid retention time (SRT), sludge retention factor (SRF), methane production rate per volume of the reactor and feed. A simultaneous increase of the variables determined a decrease of COD removal efficiency, SRT and SRF and an increase of COD removal rate, VFA/Alk., CO2 fraction in biogas, methane production rate. The present study provides valuable information about interrelations of quality and process parameters at different values of the operating variables.