Performance of an AnMBR pilot plant treating high-strength lipid wastewater: biological and filtration processes.

The performance of an anaerobic membrane bioreactor (AnMBR) treating wastewater with high levels of oil and grease content from a snacks factory is studied and its effectiveness is demonstrated. The relation between the reversible and the irreversible fouling rate and the fouling propensity of the fatty matter were evaluated under a subcritical flux of 7.9 and 8.3 L/m(2) h. Low Oil and Grease (O&G) concentrations of 500 mg/L produced an irreversible fouling rate of only 0.09 mbar/d, while the fouling rate was between 0.96 and 3.95 mbar/d for an average O&G concentration of 6 g/L. In spite of the significant increase in filtration resistance from 0.31 to 6.08 × 10(12) m(-1) after 40 days of continuous operation, the critical flux level hardly decreased from 11.1 to 9.7 L/(m(2) h). With regard to the biological process, after a start-up period with an organic loading rate (OLR) of below 2 kg COD/(m(3) d), the system was able to treat wastewater between 4.6 and 36 g O&G/L and the system remained stable for OLR at around 17 kg COD/(m(3) d) for 2.8 d, without inhibitory signals. Acclimated sludge quickly reached maximum methane production and digested substrate with high oil and grease content, observing an increase in palmitic acid the first days and constant levels of propionic acid while fatty acids were in the medium.