Optimization of alkalinity supplementation in the AnSBBR using acidified cassava starch wastewater

Abstract

In aiming to enhance performance and minimize costs, it is important to conduct research centered on the significance of alkalinity supplementation in anaerobic reactors. This study evaluated the impacts of alkalinity supplementation in the methane production, in a second-stage anaerobic sequencing batch biofilm reactor (AnSBBR) fed by acidified cassava wastewater. The AnSBBR was operated at 30 °C, cycle time (CT) of 8 and 6 h and sodium bicarbonate (gNaHCO3.gCOD[chemical oxygen demand]−1. L−1) of 1, 0.66, 0.33 and 0. The organic loading rate (OLR) were 17.1 and 22.8 gCOD.L−1d−1 for the CT of 8 and 6 h, in that order. The results showed that the reactor has been able to supply the alkalinity demand in the system, presenting removal of COD higher than 70%, even without alkalinity supplementation in the influent. The methane production rates (MPR) reached 3.42 ± 0.21 LCH4 L−1d−1 in the condition with 1 gNaHCO3.gCOD−1. L−1, with CT of 6 h. The main soluble metabolite was acetic acid and butyric acid. There was a decrease in methane production and greater instability in the reactor monitoring parameters without NaHCO3 supply. However, the degree of acidification was low, compared to the conversion of organic matter in all conditions. Thus, the AnSBBR maintained stable up to the ratio of 0.66 gNaHCO3.gCOD−1. L−1. Conditions with 1 gNaHCO3.gCOD−1. L−1. (CT 8 and 6 h) exhibited notable energy potential (≥90.2 KJ.d−1), underscoring their capacity for energy generation, even within shorter CT (6 h), thus rendering them suitable for application in industrial facilities.