Effects of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part II : oleic acid toxicity and biodegradability

摘要

Oleic acid toxicity and biodegradability were followed during long-term operation of twosimilar anaerobic fixed-bed units. When treating an oleate based effluent, the sludge from the bioreactorthat was acclimated with lipids during the first operation period, showed a higher tolerance to oleicacid toxicity (IC50=137 mg/l) compared with the sludge fed with a non-fat substrate (IC50=80 mg/l).This sludge showed also the highest biodegradation capacity of oleic acid, achieving maximum methaneproduction rates between 33 and 46 mlCH4_(STP)/gVS.day and maximum percentages of methanizationbetween 85 and 98% for the range of concentrations between 500 and 900 mg oleate/l. When oleatewas the sole carbon source fed to both digesters, the biomass became encapsulated with organic matter,possibly oleate or an intermediate of its degradation, e.g. stearate that was degraded at a maximumrate of 99 mlCH4_(STP)/gVS.day. This suggests the possibility of using adsorption-degradation cycles forthe treatment of LCFA based effluents. Both tolerance to toxicity and biodegradability of oleic acidwere improved by acclimatization with lipids or oleate below a threshold concentration.