Cleaning of Ultrafiltration Unit Fouled by Mungbean Protein

An ultrafiltration unit, the ES-30 membrane (molecular weight cut-off 30,000) was used to recover the proteins from the wastewater produced during mungbean starch processing. During ultrafiltration, the permeate flux of the unit decreased from 108.5 to 4.0 l/m2/h due to fouling and concentration polarization. The flux could be restored to 10.8, 40.7, 50.0, and 82.4 l/m2/h by washing individually with tap water, 0.5% NaOH, 0.2N HCl, and 0.75% Terg-A-enzyme, respectively. The cleaning effect was significantly affected by the cleaning agents and their concentrations. The cleaning effect of NaOH was enhanced by mixing with 0.1% Triton X-100 (a surfactant). After ultrafiltration, continuous circulation with tap water for 10 min, followed by 0.3% NaOH mixed with 0.1% Triton X-100 for 10 min, 0.2 N HCl for 10 min, and by 0.75% Terg-A-enzyme at 50°C for 30 min nearly restored the original flux of the unit. Circulation with water was immediately required after each washing with cleaning agents, especially with acid or basic solution. One and a half hours was sufficient to complete the washing process.