Polycyclic
Aromatic Hydrocarbon Affects Acetic Acid
Production during Anaerobic Fermentation of Waste Activated Sludge
by Altering Activity and Viability of Acetogen
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Abstract
Till
now, almost all the studies on anaerobic fermentation of waste
activated sludge (WAS) for bioproducts generation focused on the influences
of operating conditions, pretreatment methods and sludge characteristics,
and few considered those of widespread persistent organic pollutants
(POPs) in sludge, for example, polycyclic aromatic hydrocarbons (PAHs).
Herein, phenanthrene, which was a typical PAH and widespread in WAS,
was selected as a model compound to investigate its effect on WAS
anaerobic fermentation for short-chain fatty acids (SCFAs) accumulation.
Experimental results showed that the concentration of SCFAs derived
from WAS was increased in the presence of phenanthrene during anaerobic
fermentation. The yield of acetic acid which was the predominant SCFA
in the fermentation reactor with the concentration of 100 mg/kg dry
sludge was 1.8 fold of that in the control. Mechanism exploration
revealed that the present phenanthrene mainly affected the acidification
process of anaerobic fermentation and caused the shift of the microbial
community to benefit the accumulation of acetic acid. Further investigation
showed that both the activities of key enzymes (phosphotransacetylase
and acetate kinase) involved in acetic acid production and the quantities
of their corresponding encoding genes were enhanced in the presence
of phenanthrene. Viability tests by determining the adenosine 5′-triphosphate
content and membrane potential confirmed that the acetogens were more
viable in anaerobic fermentation systems with phenanthrene, which
resulted in the increased production of acetic acid