Prevention of Lipid Inhibition in Anaerobic Processes by Introducing a Two-Phase System

Abstract

The inhibitory effect of lipids and prevention of this inhibition in a two-phase anaerobic process were examined using laboratory-scale reactors and batch experiments. Lipids were satisfactorily degraded in a two-phase anaerobic filter while in a single-phase system, inhibition resulted in poor lipid degradation. Unsaturated long-chain fatty acids (LFAs) had a greater inhibitory effect than saturated LFAs. Methane production as well as beta-oxidation (degradation of saturated LFAs) were inhibited by unsaturated LFAs. The saturation of unsaturated LFAs was not inhibited, and palmitate (C16:0) was accumulated in the degradation of oleate (C18:l) or linoleate (C18:2). Greater inhibition was observed at low pH values. Continuous operation of a suspended-growth acidogenic reactor showed that hydraulic retention times (HRTs) of no less than 8 hours were necessary to mitigate the inhibition in a two-phase process. The fact that saturation of oleate occurred at HRTs no less than 8 hours suggests that the saturation of unsaturated LFAs in an acidogenic reactor is essential in the prevention of lipid inhibition in two-phase anaerobic processes.

Enhanced Lipid Degradation in an Upflow Anaerobic Sludge Blanket Reactor by Integration with an Acidogenic Reactor

“…The maximum lipids removal efficiency, 23.9±2.5%, was found at Period 4, while the maximum double-bond saturation, 25.2±2.9%, was found at Period 2. The maximum values were comparable to the reported values for synthetic wastewater (Komatsu et al, 1991;Kim et al, 2004a). At Period 6 and 7, both parameters decreased considerably.…”

“…A pH range of 4.0-6.5 has been reported as optimal for acidogenesis in a general two-phase system (Fox and Pohland, 1994). But, Komatsu et al (1991) reported that a low pH (6.0) hindered acidogenesis because the acidic pH changed LCFAs to an insoluble non-ionized form. It seemed that the pH values did not cause significant adverse effects on reactor performance in the whole Periods, although optimum pH for acidogenesis of lipids-containing wastewaters is still controversial.…”

“…It was reported that more double-bonded and longer LCFA was more toxic (Alosta et al, 2004). Some researchers found saturation of double-bonds in acidogenesis, and then suggested the phase separation as an alternative for the treatment of lipids-containing wastewaters (Komatsu et al, 1991). Kim et al (2004a) operated a two-phase system composed of a continuously stirred tank reactor (CSTR) and an upflow anaerobic sludge blanket (UASB) reactor as well as a single phase system of a UASB reactor, which were fed with a synthetic wastewater containing major LCFAs and glucose.…”

Early warning indicators for process failure due to organic overloading by rapeseed oil in one-stage continuously stirred tank reactor, sewage sludge and waste digesters

“…The sewage sludge consisted of excess and primary sludge from a wastewater management plant applying EBPR (enhanced biological phosphorus removal). Rapeseed oil was chosen as a co-substrate due to its high LCFA contents, such as oleic acid (52-67 %), linoleic acid (16-25 %) and linolenic acid (6-15 %), and because LCFAs are frequently found in actual wastewaters (Komatsu et al 1991). The OLR depended on the state of each experiment.…”

Anaerobic Treatments for Dairy Waste Disposal – Ponder for making it Efficient

“…This inhibition is due to the presence of long chain fatty acids formed during the hydrolysis of lipids, which causes retardation in methane production (Hanaki et al, 1981). Long chain fatty acids were reported to be inhibitory to methanogenic bacteria (Koster, 1987) but lipids do not cause serious problems in aerobic processes (Komatsu et al, 1991).…”