Influence of phenylacetic acid pulses on anaerobic digestion performance and archaeal community structure in WWTP sewage sludge digesters

Abstract

The effect of phenylacetic acid (PAA) pulses on anaerobic digestion (AD) performance and archaeal community structure was evaluated in anaerobic digesters treating sewage sludge from a wastewater treatment plant (WWTP). Four pilot-scale continuous stirred tank reactors were set up at a full-scale municipal WWTP in Santiago de Chile, and fed with either primary or mixed sewage sludge. AD performance was evaluated by volatile fatty acid (VFA) and biogas production monitoring. Archaeal community structure was characterized by 16S rRNA denaturing gradient gel electrophoresis and band sequencing. In the primary sludge digester, a single PAA pulse at 200 mg L(-1) was sufficient to affect AD performance and archaeal community structure, resulting in long-term VFA accumulation, reduced biogas production and community shift from dominant acetoclastic (Methanosaeta concilii) to hydrogenotrophic (Methanospirillum hungatei) methanogens. By contrast, AD performance and archaeal community structure in the mixed sludge digester were stable and resistant to repeated PAA pulses at 200 and 600 mg L(-1). This work demonstrated that the effect of PAA pulses on methanogenic activity and archaeal community structure differed according to AD substrate, and suggests that better insights of the correlations between archaeal population dynamics and functional performance could help to better face toxic shocks in AD.

Microbial and Phenyl Acid Dynamics during the Start-up Phase of Anaerobic Straw Degradation in Meso- and Thermophilic Batch Reactors

“…Aromatic compounds like benzoate [12], p-cresol [5], or phenylacetate (PAA) [13,14] are associated with process instability and disturbances [9]. One major source for aromatic compounds are lignocellulosic materials often found in municipal and agricultural waste materials [15].…”

“…PAA, for example, was the focus of several studies concerning aromatic compound formation and their effects on anaerobic degradation [5,8,9,13,14]. However, information on the effects of PAA on the microbial community in general and on methanogenic Archaea, in particular, is still inconclusive due to the variety of aromatic compound sources, anaerobic digestion (AD) temperature regimes, and the inocula investigated.…”

“…They considered PAA to be an appropriate indicator of impending process failures because of its low limit of detection [9]. Others found that hydrolytic and methanogenic activities, especially acetoclastic methanogenesis, can be restricted when PAA is present [14]. In another study, overload conditions caused the formation of PAA and phenylpropionate (PPA) but did not generally restrict methanogenic performance [22].…”

Microbial community dynamics in mesophilic and thermophilic batch reactors under methanogenic, phenyl acid-forming conditions

“…interactions between various microorganisms that interdependently degrade complex substrates to methane and carbon dioxide [3]. However, an increased use of waste products can be challenging due to undesirable compounds entering biogas plants [4][5][6][7]. Protein-rich waste products like slaughterhouse waste, thin stillage, or pig manure have indeed a high theoretical methane yield [8][9][10] and the resulting residues are considered desirable fertilisers [11].…”

“…The anaerobic degradation of aromatic compoundsalbeit considered distinctly slower than the aerobic approach-plays an important role in biogeochemical cycles as aromatic compounds are present in abundance in various anoxic habitats [23,24]. The phenyl acids phenylacetate (PAA) and phenylpropionate (PPA), two monocyclic aromatic acids, are relevant aromatic intermediates in the anaerobic degradation of benzenes [4,7,25]; however, these two compounds received little attention so far [15]. Anaerobic Tyr and Phe degradation by fermenting bacteria was shown to lead to the formation of PAA and 4-hydroxyphenylacetate, respectively [23].…”