Continuous Process Design Model Simulation for the Anaerobic Digestion of Vegetable Oil Wastewater

Abstract

Simulation of a mathematical model for the design of steady-state continuous reactors required for the anaerobic digestion of wastewaters was carried out. This was obtained so as to make the design of continuous stirred tank reactor (CSTR) that would be used for the anaerobic digestion of vegetable oil wastewater (VOW) possible. The model considered the kinetics of the process which has been previously determined during the batch digestion of the wastewater. The hydraulic retention time (HRT) and solid retention time (SRT) which are important parameters required for the design were estimated by varying different model parameters such as efficiency of reactor, influent substrate concentration (So) and biomass concentration (X) at various food-microorganism ratios (F/M). The HRT was calculated for different reactor efficiency (E) varying in the range of 70-95% at a constant influent substrate concentration. It was observed that the HRT increased with increase in efficiency ranging between 1.10 to 7.06 days. HRT also increased as the biomass concentration increased. SRT at constant influent substrate concentration and biomass concentration were observed to increase as the reactor efficiency increased. The effect of different substrate concentration on HRT to attain a targeted efficiency in the CSTR under steady state condition was also studied. It was observed that HRT linearly increased with increase in influent substrate concentration at constant reactor efficiency and biomass concentration. HRT also increased with decrease in biomass concentration and constant reactor efficiency for a particular substrate concentration. There was also an increase in HRT as reactor efficiency increased at constant biomass and influent substrate concentrations. SRT calculated at E1 (70%) and E2 (80%) efficiencies were observed to decrease with increase in influent substrate concentration. As the efficiencies of the reactor increased, SRT was also observed to increase. With the information obtained from the model simulation, a continuous stirred tank reactor that would treat VOW by anaerobic digestion could be designed.