Kinetics of Batch Anaerobic Digestion of Vegetable Oil Wastewater

Abstract

The treatment of vegetable oil industrial wastewater by anaerobic digestion was studied. A hydraulic retention time (HRT) of 35 days was used for the digestion process. The maximum volume of biogas production by downward displacement of water was 150ml. After digestion, the following parameters (chloride, total dissolved solids, total suspended solids, total solids total nitrogen, chemical oxygen demand, biological oxygen demand) fell within the limits prescribed by WHO (World Health Organization). The kinetic parameters such as maximum rate of substrate utilization (K), half velocity or saturation constant (Ks), endogenous decay coefficient (Kd), biomass or microbial growth yield (Y) and maximum specific microorganism growth rate (μmax) were determined as 0.8215 day 1, 163.31mg/l, 0.0838 day 1, 0.2813mg/mg and 0.231 day 1 respectively. The kinetics of anaerobic digestion of the wastewater was described by first order kinetic model. The net specific growth rates (μnet) for the wastewater also was observed to reduce with time. These values indicated that inoculation of the feed with microorganism would be required to increase the rate of digestion and therefore will require a large digester.