Fig. 2b shows the behavior of pH and alkalinity in thereactor; due to the characteristics of the wastewater and itssymbiotic relationship with the biomass, self-generated alka-linity was enough for neutralizing the changes in pH. As aconsequence of methanogenesis process, CO2is produced andreacted with free ammonia and other compounds to generatebicarbonate (HCO3−), namely alkalinity. Bicarbonate concen-tration should be 3:1 against volatile fatty acids to neutralizethem; alkalinity is used as an indicator of the stability of anaer-obic processes (Ahring et al., 1995; Pullammanappallil et al.,2001; Boe et al., 2010).