Significant increase of assimilable organic carbon (AOC) levels in MBR effluents followed by coagulation, ozonation and
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RESEARCH ARTICLE
Significant increase of assimilable organic carbon (AOC) levels in MBR effluents followed by coagulation, ozonation and combined treatments: Implications for biostability control of reclaimed water Xiaojie Shi1, Zhuo Chen (✉)1, Yun Lu1, Qi Shi1, Yinhu Wu1, Hong-Ying Hu1,2 1 Environmental Simulation and Pollution Control State Key Joint Laboratory, State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (SMARC), School of Environment, Tsinghua University, Beijing 100084, China 2 Shenzhen Environmental Science and New Energy Technology Engineering Laboratory, Tsinghua-Berkeley Shenzhen Institute, Shenzhen 518055, China
HIGHLIGHTS
GRAPHIC ABSTRACT
• Annual AOCs in MBR effluents were stable with small increase in warmer seasons. • Significant increase in AOC levels of tertiary effluents were observed. • Coagulation in prior to ozonation can reduce AOC formation in tertiary treatment. • ΔUV254 and SUVA can be surrogates to predict the AOC changes during ozonation.
ARTICLE INFO Article history:
Received 20 June 2020 Revised 4 September 2020 Accepted 15 September 2020 Available online 22 October 2020 Keywords: Assimilable organic carbon (AOC) MBR effluents Tertiary treatments Coagulation Ozonation
ABSTRACT As water reuse development has increased, biological stability issues associated with reclaimed water have gained attention. This study evaluated assimilable organic carbon (AOC) in effluents from a fullscale membrane biological reactor (MBR) plant and found that they were generally stable over one year (125–216 µg/L), with slight increases in warmer seasons. After additional tertiary treatments, the largest increases in absolute and specific AOCs were detected during ozonation, followed by coagulation-ozonation and coagulation. Moreover, UV254 absorbance is known to be an effective surrogate to predict the AOC changes during ozonation. Applying coagulation prior to ozonation of MBR effluents for removal of large molecules was found to reduce the AOC formation compared with ozonation treatment alone. Finally, the results revealed that attention should be paid to seasonal variations in influent and organic fraction changes during treatment to enable sustainable water reuse. © Higher Education Press 2020
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Introduction
Water scarcity and contamination have affected many countries, especially in hot and arid regions, and together they pose one of the greatest risks to urban sustainable
✉ Corresponding author E-mail: [email protected] (Z. Chen)
development for the next few decades (UNDESA, 2015; Sinharoy and Caruso 2019). As such, reclaimed water has been increasingly applied as an important alternative water resource to complement water supply and alleviate environmental pollution (Rock et al., 2015). Currently, reclaimed water is used not only for non-potable purposes (e.g., irrigation, industrial and domestic uses), but also for indirect and direct potable water purposes (Lazarova et al., 2013; Chen et al., 2018a; Radcliffe and Page, 2020). With
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