Low-temperature anaerobic treatment of low-strength pentachlorophenol-bearing wastewater

•Anaerobic reactors for the treatment of low-strength wastewaters at low temperature.•PCP decreases the COD removal and caused an irreversible inhibition on methanogenesis.•Inhibitory effect was modelled by modified pseudo-Monod and Roediger models.•EGSB reactor. A solution for PCP-containing wastewaters treatment at low temperature. The anaerobic treatment of low-strength wastewater bearing pentachlorophenol (PCP) at psychro-mesophilic temperatures has been investigated in an expanded granular sludge bed reactor. Using an upward flow rate of 4mh−1, a complete removal of PCP, as well as COD removal and methanization efficiencies higher than 75% and 50%, respectively, were achieved. Methanogenesis and COD consumption were slightly affected by changes in loading rate, temperature (17–28°C) and inlet concentrations of urea and oils. Pentachlorophenol caused an irreversible inhibitory effect over both acetoclastic and hydrogenotrophic methanogens, being the later more resistant to the toxic effect of pentachlorophenol. An auto-inhibition phenomenon was observed at PCP concentrations higher than 10mgL−1, which was accurately predicted by a Haldane-like model. The inhibitory effect of PCP over the COD consumption and methane production was modelled by modified pseudo-Monod and Roediger models, respectively.