Effects of Free Nitrous Acid Combined with Alkyl Polyglucoside on Short-Chain Fatty Acids Production from Waste Activated Sludge Anaerobic Fermentation and Polyhydroxyalkanoates Synthesis

Abstract

Free nitrous acid (FNA) pretreatment and alkyl polyglucoside (APG) addition are environmental-friendly methods to enhance waste activated sludge (WAS) anaerobic fermentation (AF) performances. In the current study, FNA pretreatment combined with APG addition was applied to recover short-chain fatty acids (SCFAs) from sludge AF. Experimental results indicated that 0.653 mg/L FNA+0.075 g/g VSS APG treatment could synergistically achieve the maximum total SCFAs yield of 324.94 mg COD/g VSS at day 5 of AF, which was much more than those of sole FNA or sole APG treatment. Mechanisms analysis indicated that FNA+APG treatment could promote WAS solulibization, hydrolysis and acidogenesis, while inhibit methanogenesis severely. Microbial community analysis results demonstrated that SCFAs producer, including Enterococcus and Clostridium, became the dominant genus in the FNA+APG reactor. Finally, alkali-thermal pretreated AF liquor was applied for batch-mode polyhydroxyalkanoates (PHAs) synthesis, and the PHAs yield increased to a maximum 44.44% of biomass after five periods.

Keywords: Waste activated sludge, anaerobic fermentation, Free nitrous acid, Alkyl polyglucoside, polyhydroxyalkanoates