Anaerobic acidification of sugar-beet processing wastes: Effect of operational parameters

The objective of this study was to maximize the hydrolysis and acidification of sugar-beet processing wastewater and beet pulp for volatile fatty acid (VFA) production through acidogenic anaerobic metabolism. Experiments were conducted to determine the optimum operational conditions (HRT, waste-mixing ratio and pH) for effective acidification in daily-fed, continuously mixed anaerobic reactors. For this purpose, reactors were operated at 35 ± 1 °C with different combinations of HRT (2–4 days), wastewater-pulp mixing ratios (1:0–1:1, in terms of COD) and pH ranges (5.7–7.5). Increased OLRs, resulting from pulp addition, increased the amount of acidification products (VFAs) which led to relatively low operational pH values (5.7–6.8). In this pH range, methanogenic activity was successfully inhibited and the lowest methane percentages (5.6–16.3%) were observed in the produced biogas. The optimum operational conditions were determined to be 2-day HRT and 1:1 waste mixing ratio (in terms of COD) without external alkalinity addition. These operational conditions led to the highest tVFA concentration (3635 ± 209 mg/L as H-Ac) with the acidification degree of 46.9 ± 2.1%.