Biochemical potential of methane of wastewater ultrafiltration in the processing of unriped green acerola (Malpighia emarginata).

Ultrafiltration clarifies fruit juices, in the food industry, but generates retentive, recalcitrant wastewater, which, by its organic nature, may present a potential for biodegradation and methane production. This study aimed to evaluate the biochemical methane potential (BMP) in wastewater from the processing of unripe green acerola, obtaining the mass balance and the speed of organic load removal in COD terms. The BMP assays followed the German Guidelines VDI 4630, by applying three COD loads per liter of reactor vial (0.86 g CODappliedL −1 R, 1.5 g CODappliedL−1R, and 2.0 g CODappliedL−1R), in batches, inoculated with the anaerobics ludge from reactors treating domestic sewage, at 30 ◦C. The pH, COD, and methane production were evaluated every 48 hours. The biodegradability and the decay rate constant of the COD (Kd) were determined, thus obtaining the methanized COD, the COD for the formation of new cells, and the COD present in the wastewater, in the form of volatile acids. The best BMP was 0.100 L CH4 g −1 CODremoved, the percentages of methanization were above 62 %, and the highest Kd occurred for the lowest load applied. The anaerobic digestion of the wastewater proved viable for in full-scale, with its application being suggested at a pilot scale