Long term experiences in a pilot-scale high-rate activated sludge system with lamella clarifier: Effluent quality and carbon capture

Hazal Gulhan*, Muhammed Nimet Hamidi, Amr Mustafa Abdelrahman, Malhun Fakioglu, Beyda Mese, Mustafa Yoruk, Ece Sagir Kurt, Ismail Koyuncu, Huseyin Guven, Hale Ozgun, Mustafa Evren Ersahin, Izzet Ozturk

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


The limited available area for treatment plants in population-dense settlements increases the need for technologies with smaller footprints. The high-rate activated sludge (HRAS) process aims to capture carbon from wastewater by limiting biological assimilation with a high loading rate which enables occupying a smaller footprint. The footprint of the HRAS system can be further reduced by using lamella clarifiers instead of conventional ones. Conventional clarifiers were used in previous studies on the operational parameters of the HRAS system. This study aims to determine the optimum operational conditions in terms of hydraulic retention time (HRT) (75 and 50 min) and dissolved oxygen (DO) concentration (0.2, 0.5, and 0.8 mg/L) of a HRAS system including a lamella clarifier using 124 days data. The best effluent quality and carbon capture were observed at HRT of 75 min and DO concentration of 0.5 mg/L, which was considered the optimum condition with the highest extracellular polymeric substances (EPS) production in the reactor. The high EPS production helped flocs come together and settle faster with the highest carbon capture compared to other operational conditions. Based on the mass balance, 41.7 % of chemical oxygen demand (COD), 34 % of total nitrogen (TN), and 60 % of total phosphorus (TP) in the influent were captured into the sludge stream at the optimum condition. Lower HRT and DO concentration decreased EPS production and led to particulate COD loss through effluent and hampered carbon capture. Furthermore, higher DO concentration caused more carbon loss through oxidation.

Original languageEnglish
Article number103138
JournalJournal of Water Process Engineering
Publication statusPublished - Oct 2022

Bibliographical note

Publisher Copyright:
© 2022 Elsevier Ltd


This research was funded by Istanbul Water and Sewerage Administration (ISKI) with the project titled as “Integration of High-rate Activated Sludge Process and Anaerobic Membrane Bioreactor Process for Energy Efficient Wastewater Treatment in Istanbul: Maximum Energy Recovery (MEGA2 Project)”. The authors would like to express their gratitude for the support by the Istanbul Technical University , Turkey, Scientific Research Projects: Hazal Gulhan (Project No: 42469 ) and Muhammed Nimet Hamidi (Project No: 42690 ).

FundersFunder number
Hazal Gulhan42469
Istanbul Water and Sewerage Administration
Maximum Energy Recovery
Muhammed Nimet Hamidi42690
Istanbul Teknik Üniversitesi


    • Carbon capture
    • Dissolved oxygen
    • Extracellular polymeric substances
    • High-rate activated sludge
    • Hydraulic retention time
    • Lamella clarifier


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