University of Oulu

Koivuranta, E., Suopajärvi, T., Hattuniemi, J., Stoor, T., Illikainen, M. (2017) The effect of seasonal variations on floc morphology in the activated sludge process. Environmental Technology, 38 (24), 3209-3215. doi:10.1080/09593330.2017.1291760

The effect of seasonal variations on floc morphology in the activated sludge process

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Author: Koivuranta, Elisa1; Suopajärvi, Terhi1; Hattuniemi, Joni2;
Organizations: 1Fibre and Particle Engineering Research Unit, University of Oulu, Oulu, Finland
2Valmet, Kajaani, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 2 MB)
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Language: English
Published: Informa, 2017
Publish Date: 2018-02-22


The effect of seasonal variations on floc formation in the activated sludge process (ASP) was studied in a municipal wastewater treatment plant in Finland nearly 16 months. Floc formation was measured with an online optical monitoring device, and results were correlated with the temperature of the upcoming wastewater and the treatment efficiency of the ASP. Results showed that floc formation has a clear, seasonal pattern, with flocs in summer being larger and rounder and having fewer filaments and small particles. In addition, treatment efficiency increased in summer. The study correlated the results of image analysis with the composition (chemical oxygen demand and suspended solids content) and temperature of the wastewater before and after the ASP. Results showed that the composition of upcoming wastewater has no clear correlation with floc morphological parameters. However, the wastewater temperature clearly correlated with floc formation. Results indicated that cold winter conditions enhanced the growth of filamentous bacteria in wastewater, decreasing treatment efficiency. Furthermore, these results confirmed that floc formation has seasonal variations.

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Series: Environmental technology
ISSN: 0959-3330
ISSN-E: 1479-487X
ISSN-L: 0959-3330
Volume: 38
Issue: 24
Pages: 3209 - 3215
DOI: 10.1080/09593330.2017.1291760
Type of Publication: A1 Journal article – refereed
Field of Science: 215 Chemical engineering
218 Environmental engineering
Copyright information: © 2017 Informa UK Limited, trading as Taylor & Francis Group. This is an Accepted Manuscript of an article published by Taylor & Francis in Environmental technology on 22 Feb 2017, available online: