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An efficient oxic-anoxic process for treating low COD/N tropical wastewater: Startup, optimization and nitrifying community structure

Lookup NU author(s): Professor Thomas CurtisORCiD



This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


© 2020 Elsevier LtdIn this study, we assessed and optimized a low-dissolved-oxygen oxic-anoxic (low-DO OA) process to achieve a low-cost and sustainable solution for wastewater treatment systems in the developing tropical countries treating low chemical oxygen demand-to-nitrogen ratio (COD/N) wastewater. The low-DO OA process attained complete ammonia removal and the effluent nitrate nitrogen (NO3–N) was below 0.3 mg/L. The recommended hydraulic retention time and sludge retention time (SRT) were 16 h and 20 days, respectively. The 16S rRNA sequencing data revealed that long SRT (20 days) encouraged the growth of nitrite-oxidizing bacteria (NOB) affiliated with “Candidatus Nitrospira defluvii”. Comammox made up 10–20% of the Nitrospira community. NOB and comammox related to Nitrospira were enriched at long SRT (20 days) to achieve good low-DO nitrification performance. The low-DO OA process was efficient and has simpler design than conventional processes, which are keys for sustainable wastewater treatment systems in the developing countries treating low COD/N wastewater.

Publication metadata

Author(s): How SW, Nittami T, Ngoh GC, Curtis TP, Chua ASM

Publication type: Article

Publication status: Published

Journal: Chemosphere

Year: 2020

Volume: 259

Print publication date: 01/11/2020

Online publication date: 19/06/2020

Acceptance date: 15/06/2020

Date deposited: 24/08/2020

ISSN (print): 0045-6535

ISSN (electronic): 1879-1298

Publisher: Elsevier Ltd


DOI: 10.1016/j.chemosphere.2020.127444


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Funder referenceFunder name
NA150341Royal Society