Impact of primary treatment methods on sludge characteristics and digestibility, and wastewater treatment plant-wide economics

Amr Mustafa Abdelrahman*, Sadiye Kosar, Hazal Gulhan, Busra Cicekalan, Gulin Ucas, Ezgi Atli, Huseyin Guven, Hale Ozgun, Izzet Ozturk, Ismail Koyuncu, Jules B. van Lier, Eveline I.P. Volcke, Mustafa Evren Ersahin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Biogas production from anaerobic sludge digestion plays a central role for wastewater treatment plants to become more energy-efficient or even energy-neutral. Dedicated configurations have been developed to maximize the diversion of soluble and suspended organic matter to sludge streams for energy production through anaerobic digestion, such as A-stage treatment or chemically enhanced primary treatment (CEPT) instead of primary clarifiers. Still, it remains to be investigated to what extent these different treatment steps affect the sludge characteristics and digestibility, which may also impact the economic feasibility of the integrated systems. In this study, a detailed characterization has been performed for sludge obtained from primary clarification (primary sludge), A-stage treatment (A-sludge) and CEPT. The characteristics of all sludges differed significantly from each other. The organic compounds in primary sludge consisted mainly of 40% of carbohydrates, 23% of lipids, and 21% of proteins. A-sludge was characterized by a high amount of proteins (40%) and a moderate amount of carbohydrates (23%), and lipids (16%), while in CEPT sludge, organic compounds were mainly 26% of proteins, 18% of carbohydrates, 18% of lignin, and 12% of lipids. The highest methane yield was obtained from anaerobic digestion of primary sludge (347 ± 16 mL CH4/g VS) and A-sludge (333 ± 6 mL CH4/g VS), while it was lower for CEPT sludge (245 ± 5 mL CH4/g VS). Furthermore, an economic evaluation has been carried out for the three systems, considering energy consumption and recovery, as well as effluent quality and chemical costs. Energy consumption of A-stage was the highest among the three configurations due to aeration energy demand, while CEPT had the highest operational costs due to chemical use. Energy surplus was the highest by the use of CEPT, resulting from the highest fraction of recovered organic matter. By considering the effluent quality of the three systems, CEPT had the highest benefits, followed by A-stage. Integration of CEPT or A-stage, instead of primary clarification in existing wastewater treatment plants, would potentially improve the effluent quality and energy recovery.

Original languageEnglish
Article number119920
JournalWater Research
Volume235
DOIs
Publication statusPublished - 15 May 2023

Bibliographical note

Publisher Copyright:
© 2023 Elsevier Ltd

Funding

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 PhD Fellowship awards provided by the Turkish Academy of Sciences (TUBA) to Amr Mustafa Abdelrahman. The authors would like to express their gratitude for the support by the Istanbul Technical University, Turkey, Scientific Research Projects: Amr Mustafa Abdelrahman [Project No: MDK-2021-42990]. 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 PhD Fellowship awards provided by the Turkish Academy of Sciences (TUBA) to Amr Mustafa Abdelrahman. The authors would like to express their gratitude for the support by the Istanbul Technical University, Turkey, Scientific Research Projects: Amr Mustafa Abdelrahman [Project No: MDK-2021-42990 ].

FundersFunder number
Amr Mustafa AbdelrahmanMDK-2021-42990
ISKI
Istanbul Water and Sewerage Administration
Maximum Energy Recovery
TUBA
Türkiye Bilimler Akademisi
Istanbul Teknik Üniversitesi

    Keywords

    • A-stage
    • Biochemical methane potential
    • Chemically enhanced primary treatment
    • Economic evaluation
    • Physicochemical characteristics
    • Primary clarification

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