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 tox icity of CHCl3, CCl4, C2H2Cl4 and trans-C2H2Cl2 on the acetoclastic me thanogenic activity of anaerobic sludge was studied. The following con clusions were derived: (i) The extend of inhibition produced is a func tion of the toxicant concentration, the type and the amount of the bio mass. A lag-period was detected for the inhibition produced by CHCl3 a nd trans-C2H2Cl2, while for the other compounds the inhibitory effect was instant. (ii) The recovery time for an anaerobic granular sludge e xposed to different toxicants was a function of the extent of inhibiti on and the exposure time, and seemed to be independent of the toxicant s used. (iii) The possible acclimatization of an anaerobic sludge to c ontinuous exposure to a toxicant was dependent on the nature of the to xicant. The time required to acquire an activity similar to that of un treated controls was dependent on the concentration of the toxicant us ed. In our case adaptation mas only obtained for CCl4.