Vol. 25, No. 2 (2026), IA26745 https://doi.org/10.24275/rmiq/IA26745

Sodium bicarbonate as an acid–base modulator in anaerobic digestion of acidic candy wastewater

 

Authors

J.M. Montes-González, R. Beristain-Cardoso, G. González-Blanco

Abstract

This study investigates the role of sodium bicarbonate as an acid–base modulator during the anaerobic digestion of real wastewater from the candy industry (pH 4.2). Although pH correction is necessary for activating methanogenic pathways, quantitative guidance on bicarbonate requirements for highly acidic effluents remains limited. Batch assays were therefore conducted using metabolically stable UASB sludge to evaluate the effects of increasing NaHCO3 concentrations (3–6 g/L) on COD removal, biochemical methane potential (BMP), buffering capacity (α-factor), and lag phase duration. In the absence of pH adjustment, COD removal was negligible, confirming the strong inhibition imposed by extreme acidity. The addition of 3 gNaHCO3/L raised the initial pH to 6.54 and enabled 32.9% COD removal, while higher concentrations (4–6 g NaHCO3/L) achieved 79.3–85.0% removal. Methane production declined with increasing alkalinity: BMP decreased from 68.8 to 36.0–43.9 mL CH4/g COD consumed at 5–6 g NaHCO3/L, likely due to elevated sodium levels (up to 1.64 g Na⁺/L). The α-factor increased from 0.49 to 0.64, indicating enhanced buffering and process stability, while the lag phase shortened, suggesting sodium-stimulated metabolic activity. Overall, excessive buffering suppresses methanogenesis, underscoring the need for optimized neutralization to balance methane production and organic matter removal.

Keywords

buffering-capacity, sodium bicarbonate, acidic water, methane, inhibition.

References
  • Alvarado-Reyna, P.M., Albalate-Ramírez, A., García-Balandrán, E.E., Escamilla-Alvarado, C., Galván-Arzola, U., Miramontes-Martínez, L.R. and Rivas-García, P. (2024). Evaluation of the reaction capacity of early warning indicators to failures in biogas production systems. Revista Mexicana de Ingeniería Química 23(3), 1–19. https://doi.org/10.24275/rmiq/Bio24313
  • APHA, 2005. Standard Methods of Water and Wastewater. 21st Edn., American Public Health Association, Washington, DC., ISBN: 0875530478, pp: 2-61.
  • Beschkov, V.N. and Angelov, I.K. (2025). Volatile fatty acid production vs. methane and hydrogen in anaerobic digestion. Fermentation 11(4), 172. https://doi.org/10.3390/fermentation11040172
  • Cisneros de la Cueva, S., Veana Hernández, F., Arjona López, M.A., Alvarez Guzmán, C. L. and Pérez Vega, S.B. (2021). Optimización de las variables del proceso de digestión anaerobia de lactosuero en la producción de biogás. Revista Internacional de Contaminación Ambiental 37, 307-318. https://doi.org/10.20937/RICA.53879
  • Filer, J., Ding, H.H. and Chang, S. (2019). Biochemical methane potential (BMP) assay method for anaerobic digestion research. Water 11(5), 921. https://doi.org/10.3390/w11050921
  • Henriquez, T., Wirtz, L., Su, D. and Jung, H. (2021). Prokaryotic solute/sodium symporters: versatile functions and mechanisms of a transporter family. International Journal of Molecular Sciences 22(4), 1880. https://doi.org/10.3390/ijms22041880
  • Gómez-Paredes, M.D., Hernández-Rodríguez, I.A., López-Ortega, J., González-Blanco, G. and Beristain-Cardoso, R. (2020). Industrial wastewater treatment by anaerobic digestion using a solar heater as renewable energy for temperature-control. Revista Mexicana de Ingeniería Química 19(1), 9–16. https://doi.org/10.24275/rmiq/IA1853
  • Jenkins, S.R., Morgan, J.M. and Sawyer, C.L. (1983). Monitoring anaerobic sludge digestion and growth by simple alkalimetric titration. Water Pollution Control Federation 55(5), 448–453. https://www.jstor.org/stable/25041903
  • Latif, M.A., Mehta, C.M. and Batstone, D.J. (2017). Influence of low pH on continuous anaerobic digestion of waste activated sludge. Water Research 113 (15), 42–49. https://doi.org/10.1016/j.watres.2017.02.002
  • Lefebvre, O., Vasudevan, N., Torrijos, M., Thanasekaran, K. and Moletta, R. (2005). Halophilic biological treatment of tannery soak liquor in a sequencing batch reactor. Water Res 39(8), 1471–1480. https://doi.org/10.1016/j.watres.2004.12.038
  • Loreto-Muñoz, C.D., López-Avilés, G., De la Cruz-Leyva, M.C., Martin-García, A.R. and Almendariz-Tapia, F.J. (2024). Sulfidogenic activity related to microbial diversity in a biological system employed for sulfate-rich wastewater treatment. Revista Mexicana de Ingeniería Química 23(1), 1-11. https://doi.org/10.24275/rmiq/IA24167
  • Mao, C., Feng, Y., Wang, X. and Ren, G. (2015). Review on research achievements of biogas from anaerobic digestion. Renewable and Sustainable Energy Reviews 45, 540–555. https://doi.org/10.1016/j.rser.2015.02.032
  • Mei, W., Li, L., Zhao, Q., Li, X., Wang, Z., Gao, Q., Wei, L., Wang, K. and Jiang, J. (2025). A critical review of effects, action mechanisms and mitigation strategies of salinity in anaerobic digestion. Renewable and Sustainable Energy Reviews 208, 115095. https://doi.org/10.1016/j.rser.2024.115095
  • Pérez, A. and Torres, P. (2008). Índices de alcalinidad para el control del tratamiento anaerobio de aguas residuales fácilmente acidificables. Ingeniería y Competitividad 10(2), 41–52. https://doi.org/10.25100/iyc.v10i2.2473
  • Serrano-Meza, A., Garzón-Zúñiga, M. A., Barragán-Huerta, B. E., Estrada-Arriaga, E. E., Almaraz-Abarca, N. and García-Olivares, J. G. (2020). Anaerobic digestion inhibition indicators and control strategies in processes treating industrial wastewater and wastes. Revista Mexicana de Ingeniería Química 19(1), 29–44. https://doi.org/10.24275/rmiq/IA1221 
  • Qiu, S., Zhang, X., Xia, W., Li, Z., Wang, L., Chen, Z. and Ge, S. (2023). Effect of extreme pH conditions on methanogenesis: Methanogen metabolism and community structure. Science of Total Environment 877(15), 162702. https://doi.org/10.1016/j.scitotenv.2023.162702
  • Rabii, A., Aldin, S., Dahman, Y. and Elbeshbishy, E. (2019). A review on anaerobic co-digestion with a focus on the microbial populations and the effect of multi-stage digester configuration. Energies 12(6), 1106. https://doi.org/10.3390/en12061106
  • Silva, A.J., Pozzi, E., Foresti, E. and Zaiat, M. (2015). The influence of the buffering capacity on the production of organic acids and alcohols from wastewater in anaerobic reactor. Applied Biochemistry and Biotechnology 175, 2258–2265. https://doi.org/10.1007/s12010-014-1424-y
  • Xiao, K., Maspolim, Y., Zhou, Y., Guo, C. and Ng, W.J. (2022). Effect of sodium on methanogens in a two-stage anaerobic system. Applied Sciences 12(3), 956. https://doi.org/10.3390/app12030956