Polycyclic Aromatic Hydrocarbon Affects Acetic Acid Production during Anaerobic Fermentation of Waste Activated Sludge by Altering Activity and Viability of Acetogen

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.

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Novel stepwise pH control strategy to improve short chain fatty acid production from sludge anaerobic fermentation

“…Waste activated sludge (WAS), the main byproduct of the wastewater treatment plant (WWTP), is produced with substantial quantities daily. Studies reported recently that annual output of sludge in China was up to 34 million metric tonnes (80% water content), and with continuous development of urbanization process, the annual output of WAS will be greater in the future (Wang et al, 2015;Luo et al, 2016;Zhao et al, 2015a).…”

“…), so consequently WAS is also a valuable renewable resource. However, around 80% of WAS is squandered in many WWTPs via incineration or landfill (Luo et al, 2016). Therefore, how to effectively recover energy from WAS and achieve the reduction and harmless of WAS simultaneously have attracted growing scientific interest (Zhao et al, 2015b;Yang et al, 2015).…”

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