Positive impact of a reducing agent on autotrophic nitrogen removal process and nexus of nitrous oxide emission in an anaerobic downflow hanging sponge reactor. (October 2020)

• Record Type: Journal Article
• Authors: Tran P., Thao; Hatamoto, Masashi; Tsuba, Daisuke; Watari, Takahiro; Yamaguchi, Takashi
• Is Part Of: Chemosphere. Volume 256(2020)
• Publication Date: 2020-10
• Subjects: DAMO -- DHS reactor -- Titanium(III) nitrilotriacetate -- N2O emission -- Autotrophic denitrification; Anammox anaerobic ammonium oxidation -- AOB ammonium-oxidizing bacteria -- DAMO denitrification coupled to anaerobic methane oxidation -- DHS downflow hanging sponge -- DIN dissolved inorganic nitrogenous -- DO dissolved oxygen -- HRT hydraulic retention time -- NOB nitrite-oxidizing bacteria -- NOx− NO2− and NO3− -- Nr reactive nitrogen -- NTA nitrilotriacetic acid -- PN partial nitrification -- SBR sequencing batch reactor -- Tg tera gram (1012 g) -- Ti(III)-NTA titanium(III) nitrilotriacetate; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2020.126952
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The adjustment of hydraulic retention time (HRT) and the supplement of titanium(III) nitrilotriacetate (Ti(III)-NTA) as a reducing agent were implemented in an anaerobic downflow hanging sponge (DHS) reactor with the aims to (i) improve nitrogen removal performance and to (ii) eliminate N2 O emission. A laboratory-scale DHS reactor was operated at 35 °C, under autotrophic denitrification conditions with methane gas (14.2 L d −1 ) as the main carbon source, NaNO3 and NaNO2 (20 mg N L −1 per compound) as nitrogen sources. The sufficient HRT for simultaneously removing nitrate and nitrite in this reactor was found at 12 h when HRT was reduced from 24 to 6 h. Then at the HRT of 12 h, the addition of Ti(III)-NTA at a final concentration of 25 μM Ti(III) boosted the reactor's nitrogen removal rates from 1.4 ± 0.6 to 4.1 ± 1.9 g NO3 − -N m −3 d −1 and 3.2 ± 2.8 to 6.6 ± 3.3 g NO2 − -N m −3 d −1 . Furthermore, this study is the first to consider the N2 O emission in a continuous reactor applying denitrification coupled to anaerobic methane oxidation (DAMO) process. Produced N2 O in this DHS reactor was from 10.6 × 10 −4 % to 89.0 × 10 −4 % of removed NOx − without Ti(III)-NTA and from 0.7 × 10 −4 % to 61.4 × 10 −4 % of removed NOx − with Ti(III)-NTA. Overall, these findings suggested the advantage of Ti(III)-NTA as an oxygen scavenger for denitrification processes and the potential of the anaerobic DHS reactor for facilitating the DAMO processes and mitigating N2 O gas. Highlights: The closed-type DHS reactor emitted only a trace amount of N2 O. Shorten HRT caused an increase in NO2 − loading rate to a toxic level. Ti(III)-NTA solution is an effective oxygen scavenger without any inhibition. N2 O emission was irrelevant to NOx − removal in the DAMO processes.