Pilot-Scale Study of the Anaerobic Membrane Bioreactor Process for Treatment of a Salad Dressing Wastewater

A pilot-scale anaerobic membrane bioreactor (AnMBR) system was operated at a salad dressings and barbeque sauce production facility for six months to investigate the suitability of the ADIAnMBR process for upgrading the existing wastewater treatment system to treat additional flow and load. Lack of space and superior economics made converting the existing anaerobic process to AnMBR an attractive option. The AnMBR pilot operated under three operating conditions at mesophilic temperature. Two operating conditions involved treating the existing anaerobic reactor supernatant recycle stream at organic loading and membrane flux rates of 4.5 – 6.5 kg COD/m3-d and 0.10 – 0.133 m3/m2·d, respectively. The third operating condition involved treating raw wastewater directly in the AnMBR pilot at the same design organic loading (2.0 kg COD/m3-d) and membrane flux rates (0.10 m3/m2·d) as the proposed AnMBR system. The AnMBR pilot system consistently provided BOD removals over 99 percent when directly treating raw wastewater, and in combination with the existing anaerobic reactor when treating the anaerobic reactor supernatant recycle. Over the 24 weeks of AnMBR piloting, the AnMBR effluent BOD and TSS concentrations were consistently less than 100 mg/l and 1 mg/l, respectively. The pilot exhibited negligible fouling (with no citric acid cleaning) over an operating period of 162 days and successfully operated at a sustained peak flux rate of 0.133 m3/m2·d.