SULFIDE INHIBITION OF METHANOGENIC ACTIVITY AT VARIOUS PH LEVELS AT 55-DEGREES-C

The purpose of this study was to evaluate the toxic effect of sulphide on thermophilic methanogenic bacteria, pre-cultivated in UASB-reactor s fed with and without sulphate, at 55-degrees-C and different pH leve ls. For granular sludge, pre-cultivated in the presence of sulphate, t he inhibition caused by hydrogen sulphide was dependent on the pH impo sed. At alkaline pH the inhibitory effect of hydrogen sulphide was hig her than at neutral or acidic pH. The effect of sulphide could not be described in terms of free hydrogen sulphide level only. For dispersed sludge, pre-cultivated in the absence of sulphate, the inhibition cau sed by free hydrogen sulphide was independent of the pH, and the toxic effect of sulphide could be described in terms of free hydrogen sulph ide.