Comparative toxicity of long-chain fatty acid to anaerobic sludges from various origins

Abstract

Seven anaerobic sludges were screened in order to obtain the most suitable methanogenic inoculum for the anaerobic treatment of wastewaters containing long-chain fatty acids (LCFA). The selection was made on the basis of the toxicity of a model compound, oleate, to acetoclastic methanogens in different sludges. The effects of three biological factors, sludge origin, specific acetoclastic methanogenic activity and sludge adaptation to lipids, and a physical factor, specific surface area of sludge, on the degree of toxicity were investigated and compared. Values of the fifty percent inhibition concentration (IC50) of oleate obtained from 40°C batch toxicity tests ranged from 0.26 to 3.34 mM for the various sludges examined. It was found that the toxicity of oleate to anaerobic sludges was not dependent upon the three biological factors. Instead, it was closely correlated to the specific surface area of sludge. Suspended and flocculent sludges, which have higher specific surface area, suffered much greater inhibition than did granular sludges. This paper suggests the use of granular sludges as appropriate inocula for reactors treating lipids (fats, oils and greases) wastewaters, to decrease the toxic impact from their hydrolysis products-LCFA.

Low strength ultrasonication positively affects the methanogenic granules toward higher AD performance. Part I: Physico-chemical characteristics

“…It appears that the propagated ultrasonic wave generated the numerous craters on the surface of the methanogenic granules; the greater amount of produced biogas resulted in much bigger and deeper cracks than the control granules. As a result of a rougher and more uneven surface, 2.3 times higher specific surface area was observed from the ultrasonicated granules (0.5337 ± 0.0036 m 2 /g TS) than the control granules (0.1624± 0.0025 m 2 /g TS), which were in a range of previously reported values (0.02-0.074 m 2 /g TS) (Hwu et al, 1996). Higher specific surface area, implying an increase of the contact frequency between the substrate and microorganism, appears to be a more favorable condition for the microbial reactions.…”

Assessment of sediment toxicity during anaerobic biodegradation of vegetable oil using Microtox® and Hyalella azteca bioassays

“…1(b)]. Although it is biodegradable, anaerobic metabolism of vegetable oil may produce intermediates that are inhibitory to aceticlastic methanogens and hydrogen-producing acetogens (Hanaki et al, 1981;Koster and Cramer, 1987;Hwu et al, 1996;Lalman and Bagley, 2001). Such inhibition was observed during anaerobic degradation of vegetable oil in freshwater sediments (Li et al, 2001(Li et al, , 2005.…”

“…Free long-chain fatty acids have been reported to be toxic to a wide variety of microorganisms in anaerobic digestion systems (Hanaki et al, 1981;Koster and Cramer, 1987;Rinzema et al, 1994;Hwu et al, 1996;Lalman and Bagley, 2001;Pereira et al, 2001Pereira et al, , 2003a. Transient sediment toxicity was also observed during the anaerobic biodegradation of vegetable oil in freshwater sediments (Li and Wrenn, 2004).…”

Mississippi State Biodiesel Production Project

“…Although some information was known about modeling of MWWTFs, the demand for a more complete operational picture called for increased model complexity. For example, it was found that long-chain fatty acids produce various toxic effects during anaerobic digestion [6,7]. Anaerobic digestion refers to the reduction of sludge mass through bacterial metabolism in the absence of oxygen.…”