Fig. 3From: Potential of acetic acid to restore methane production in anaerobic reactors critically intoxicated by ammonia as evidenced by metabolic and microbial monitoringProgress over time of the biogas concentrations in CH4, CO2, H2 and H2S for: a, b the LNR reference reactor, c, d the free ammonia intoxicated reactor, HNR1, e, f HNR2 and g, h HNR3. CH4 and CO2 concentrations are expressed in volume/volume percents (%v/v). H2 and H2S concentrations are expressed in parts per million by volume (ppmv). Measurements could not be performed from week 1 to week 3 due to the interruption of the biogas production (hatched grey area). “Process reconditioning I, II, III”, “Process recovery” and “Process stability test” refer to the stages and phases described in Table 1Back to article page