초록
Batch and continuous anaerobic tests were used to study the effect of cleaning additives on the methane production from brewery effluents. The detergents studied were based on fatty acids esters or on ethoxilated alcohols and presented EC<SUB>50</SUB> values in Vibrio fischeri of 4.3 and 14.1g/L respectively. However, these detergents were toxic to the granular sludge even at lower concentrations indicating that some of the microorganisms presented in the granular sludge were more sensitive than the Vibrio fischeri. Comparing batch and continuous tests, it was observed that under continuous conditions the toxicity was lower than under batch conditions, indicating the capability of the microorganisms to get acclimatised, in the long term, to the surfactants. In the case of the detergent based on ethoxilated alcohols, the microorganisms were capable to acclimatise even at concentrations of 1000mg/L, however in the case of the detergents based on fatty acids esters, concentrations higher than 500mg/L caused toxicity. This toxic effect reduced the methane production significantly, reducing the energy recovery from the wastewater to about a 35% of the original value. From the results it was concluded that the detergents based on ethoxilated alcohols were more adequate than the detergent based on fatty acids esters because of its toxic effect towards granular sludge.