Significant production of nitric oxide by aerobic nitrite reduction at acidic pH

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Xi Lu
  • Zhiyao Wang
  • Haoran Duan
  • Ziping Wu
  • Shihu Hu
  • Liu Ye
  • Min Zheng

Detail(s)

Original languageEnglish
Article number119542
Journal / PublicationWater Research
Volume230
Online published29 Dec 2022
Publication statusPublished - 15 Feb 2023
Externally publishedYes

Abstract

The acidic (i.e., pH ∼5) activated sludge process is attracting attention because it enables stable nitrite accumulation and enhances sludge reduction and stabilization, compared to the conventional process at neutral pH. Here, this study examined the production and potential pathways of nitric oxide (NO) and nitrous oxide (N2O) during acidic sludge digestion. With continuous operation of a laboratory-scale aerobic digester at high dissolved oxygen concentration (DO>4 mg O2 L−1) and low pH (4.7±0.6), a significant amount of total nitrogen (TN) loss (i.e., 18.6±1.5% of TN in feed sludge) was detected. Notably, ∼40% of the removed TN was emitted as NO, with ∼8% as N2O. A series of batch assays were then designed to explain the observed TN loss under aerobic conditions. All assays were conducted with a low concentration of volatile solids (VS), i.e., VS<4.5 g L−1. This VS concentration is commensurate with the values commonly found in the aeration tanks of full-scale wastewater treatment systems, and thus no significant nitrogen loss should be expected when DO is controlled above 4 mg O2 L−1. However, nitrite disappeared at a significant rate (with the chemical decomposition of nitrite excluded), leading to NO production in the batch assays at pH 5. The nitrite reduction could be associated with endogenous microbial activities, e.g., nitrite detoxification. The significant NO production illustrates the importance of aerobic nitrite reduction during acidic aerobic sludge digestion, suggesting this process cannot be neglected in developing acidic activated sludge technology. © 2022 Elsevier Ltd

Research Area(s)

  • Acidic activated sludge processes, Biological NO production, Microbial detoxification, Nitrogen loss, Sludge digestion

Citation Format(s)

Significant production of nitric oxide by aerobic nitrite reduction at acidic pH. / Lu, Xi; Wang, Zhiyao; Duan, Haoran et al.
In: Water Research, Vol. 230, 119542, 15.02.2023.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review