Feasibility of nanofiltration process for high efficient recovery and concentrations of food waste-derived volatile fatty acids

Various methods exist for the recovery of volatile fatty acids from organic mixed waste effluents, and among them, the membrane filtration process holds a great promise over other recovery methods due to their simplicity, sustainability and high efficiency. Hence, in this study, nanofiltration experiments were carried out using two commercial nanofiltration membranes of 200-300 Da and 300-500 Da under various pH (4, 5.4, 7 and 9) at constant pressure (15 bar) and temperature of 20-21 degrees C in order to achieve a higher amount of volatile fatty acids from the real mixed food waste-based effluent. Results showed that solution pH plays an important role in the physicochemical parameters such as total solids removal rate was above 80 % at pH 4, chemical oxygen demand, ammonia and phosphorus removed to some extent at pH 9. Subsequently, the concentration and recovery percentages of volatile fatty acids increased with solution pH 9; in particular, lower molecular weight cut-off membrane, i.e., 200-100 Da, appeared to be more effective with an increased concentration of total volatile fatty acids (16.94 g L-1) and recovery percentage above 90 % at pH 9. Membrane performance was also evaluated and correlated with recovery performance in terms of permeate flux reduction at lower pH. An important finding of this study was the concentration and recovery percentages of volatile fatty acids reached around 96 % after 3rd cycle by conducting a repeated sequencing nanofiltration process, which was identified as a promising option to enhance the recovery percentages of volatile fatty acids.

Automated summary

This study investigated the recovery of volatile fatty acids from mixed food waste effluent using nanofiltration. The results showed that solution pH played a crucial role in the physicochemical parameters and recovery percentages of volatile fatty acids. Lower molecular weight cut-off membranes were found to be more effective, especially at higher pH. Additionally, conducting a repeated sequencing nanofiltration process significantly enhanced the recovery percentages of volatile fatty acids.