The inhibition of sulfide, nitrite, and recalcitrant carbon on anammox process was studied. Maximum specific anammox activity (MSAA) based on N₂ production rates was determined for NO₂-N from 50 - 600 mg N/L, sulfide from 1 – 15 mg S/L, and thermal hydrolysis process filtrate from 0 – 100% (with dissolved organic carbon of 600 mg/L at 100%). MSAA increased with the increasing nitrite concentrations from 50 to 150 mg N/L at which the highest MSAA at 50.6 mg N₂/h●g VSS was recorded. At 200 mg N/L of nitrite and above, MSAA decreased as nitrite concentration increased and at 600 mg N/L, MSAA dropped 70% from its highest. Nitrite inhibition coefficient was calculated using Edward model with K_IE was 435 mg N/L. The presence of sulfide had an immense impact on MSAA, which markedly dropped as sulfide concentration increased. At 15 mg S/L of sulfide, Anammox activity was almost completely inhibited, as MSAA dropped 80% compared to control (without sulfide). Sulfide inhibition was fitted using first-order reaction model with a coefficient K of -0.1 L/mg S. THP filtrate at 100% had minimal effect on MSAA with only 12% reduction compared to control (0% filtrate). Anammox activity could be recovered entirely after repeated and prolonged exposures to nitrite up to 400 mg N/L, and filtrate at 100%, while 32% and 10% were recovered for sulfide at 2.5 and 5 mg S/L. The hzsB gene, anammox biomarker, expressions were increased when incubated with nitrite at 50, 200 and 400 mg N/L, filtrate at 100% and sulfide at 2.5 mg S/L; except at 5 mg S/L of sulfide. Results from this study improve our understandings of anammox inhibition by NO₂^-, S^2- and recalcitrant carbon at the gene level. These understandings help for troubleshooting as well as improving the efficiency of the anammox reactor.

Soklida Hong

University of Utah

Appearances