pH measurements taken from anaerobic digestion (AD) processes show fluctuations with an apparent random behavior that is usually associated to noise. However, it is well-known that the AD process is carried out on the basis of electron interchange from donors to acceptors. Therefore, such a random behavior could be associated to the current conditions governing the process behavior and then, a suitable analysis can provide important insights into the dynamical behavior and operational stability of AD processes. In this work, fractal scaling properties of pH signals from different continuous anaerobic bioreactors (applied to the treatment of tequila vinasses) are analyzed by using R/S analysis. Results indicated that fractal dimension is directly related to key process variables (influent COD, VFA and biogas production). This findings are helpful to achieve better insight into the operational aspects of continuous anaerobic digesters.