Pattaraporn KunapongkitiTawan LimpiyakornPrinpida SonthiphandChaiwat RongsayamanontChulalongkorn UniversityMahidol UniversityPrince of Songkla UniversityResearch Network of NANOTEC-CU (RNN) on EnvironmentResearch Program: The Development of Management System for Reduction and Control of Water Contamination and Distribution in Songkhla Lake Basin and the Western Coastline of the South of Thailand2020-01-272020-01-272019-07-29Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering. Vol.54, No.9 (2019), 874-88315324117109345292-s2.0-85064611930https://repository.li.mahidol.ac.th/handle/123456789/50910© 2019, © 2019 Taylor & Francis Group, LLC. In this study, we investigated the effect of different cell-to-matrix ratios (1% and 4%) on the partial nitrification of phosphorylated polyvinyl alcohol-entrapped-cell-based reactors and evaluated the microenvironment, microbial community, and microbial localization within the gel matrices. The results indicated that the reactor with a 1% cell-to-matrix ratio required 184 days of operation to reach partial nitrification that produced anaerobic ammonium oxidation-suitable effluent. In contrast, partial nitrification was achieved from the beginning of the operation of the reactor with the 4% cell-to-matrix ratio. The oxygen-limiting zone (dissolved oxygen = 0.5–1.5 mg L−1), where nitrite-oxidizing activity has been suggested to be suppressed and ammonia-oxidizing activity was reported to be maintained, occurred at 10–230 µm from the gel matrices surface. In addition, the layer of ammonia-oxidizing bacteria observed in this zone is likely to have played a role in obstructing oxygen penetration into the inner region of the gel matrices. The next-generation sequencing results indicated that members of the family Nitrosomonadaceae accounted for 16.4–20.7% of the relative abundance of bacteria at the family level, while members of the family Bradyrhizobiaceae, to which the genus Nitrobacter belongs, accounted for approximately 10% of the relative abundance of bacteria at the genus level in the gel matrices.Mahidol UniversityEnvironmental ScienceArticleSCOPUS10.1080/10934529.2019.1604011