Response of an anaerobic granular sludge to chlorinated aliphatic hydrocarbons in different conditions

In spite of its importance, little attention has been paid thus far to the toxicity of chlorinated aliphatic hydrocarbons under methanogenic conditions. The effect of several parameters which can affect the toxicity of CHCl₃, CCl₄, C₂H₂Cl₄ and trans-C₂H₂Cl₂ on the acetoclastic methanogenic activity of anaerobic sludge was studied. The following conclusions were derived: (i) The extend of inhibition produced is a function of the toxicant concentration, the type and the amount of the biomass. A lag-period was detected for the inhibition produced by CHCl₃ and trans-C₂H₂Cl₂, while for the other compounds the inhibitory effect was instant. (ii) The recovery time for an anaerobic granular sludge exposed to different toxicants was a function of the extent of inhibition and the exposure time, and seemed to be independent of the toxicants used. (iii) The possible acclimatization of an anaerobic sludge to continuous exposure to a toxicant was dependent on the nature of the toxicant. The time required to acquire an activity similar to that of untreated controls was dependent on the concentration of the toxicant used. In our case adaptation was only obtained for CCl₄.