Journal
JOURNAL OF HAZARDOUS MATERIALS
Volume 459, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.jhazmat.2023.132284
Keywords
Sewer; Free nitrous acid (FNA); Ferric hydrolysis; Enzymes and genes; Microbial metabolic behavior; Greenhouse gas
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This study reveals the feasibility of using ferric chloride combined with nitrite for generating free nitrous acid (FNA) to control sulfide and methane. The use of FeCl3 as an alternative acid source can reduce chemical costs and N2O emissions while affecting the activity of the complex syntrophic consortium.
Ferric chloride (FeCl3) served as a solid acid has attracted attention recently. However, the feasibility of FeCl3 combined with nitrite for free nitrous acid (FNA) generation in controlling sulfide and methane as well as the triggering mechanisms in the complex syntrophic consortium (i.e., sewer biofilm) remain largely unknown. This work disclosed FeCl3 as an alternative acid source could obtain comparable sulfide and methane mitigations at a low FNA dose (i.e., 0.26 mg N/L), compared to that of HCl acid source. Whereas, a faster recovery rate of sulfide production was observed using FeCl3 under a higher FNA dose (i.e., 0.81 mg N/L) despite the methane control still being comparable. The toxicological mechanisms revealed FNA reacted with proteins amide I in extracellular polymeric substances and destroyed protein hydrogen bond. Enzymatic and genic analysis unveiled the overall suppression of hydrolysis, acidogenesis, acetogenesis, sulfidogenesis and methanogenesis steps due to the inactivation of viable cells by reactive nitrogen species. Economic and environmental assessments demonstrated that the ferric-based FNA strategy reduced chemical costs and N2O emission (ca. 26.5% decrease) compared to the traditional HCl-based FNA method. This work broadens the application of iron salt-based technology in urban water system, together with understanding the biological mechanisms of FNA-based technology.
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