Highly efficient carbon assimilation and nitrogen/phosphorus removal facilitated by photosynthetic O2 from algal-bacterial aerobic granular sludge under controlled DO/pH operation

• Published in: Water research (Oxford) Vol. 238; p. 120025
• Main Authors: Li, Zejiao, Wang, Jixiang, Liu, Jialin, Chen, Xingyu, Lei, Zhongfang, Yuan, Tian, Shimizu, Kazuya, Zhang, Zhenya, Lee, Duu-Jong, Lin, Yuemei, Adachi, Yasuhisa, van Loosdrecht, Mark C.M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 30.06.2023
• Subjects: Algal-bacterial aerobic granular sludge; Carbon fixation; Nitrogen assimilation; Photosynthetic oxygen; Simultaneous nitrogen and phosphorus removal; Photosynthetic oxygen; Algal-bacterial aerobic granular sludge; Simultaneous nitrogen and phosphorus removal; Carbon fixation; Nitrogen assimilation
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2023.120025

•Algal-bacterial AGS biomass assimilated 52% of influent dissolved total C.•Photosynthetic O2 is enough for highly efficient N/P removal by algal-bacterial AGS.•Simultaneous nitrification/denitrification is one of major N removal pathways.•92–98% P removal is mainly contributed by PAOs in the proposed granule system. Reducing CO2 emission and energy consumption is crucial for the sustainable management of wastewater treatment plants (WWTPs). In this study, an algal-bacterial aerobic granular sludge (AGS) system was developed for efficient carbon (C) assimilation and nitrogen (N)/phosphorus (P) removal without the need for mechanical aeration. The photosynthetic O2 production by phototrophic organisms maintained the dissolved oxygen (DO) level at 3-4 mg/L in the bulk liquid, and an LED light control system reduced 10–30% of light energy consumption. Results showed that the biomass assimilated 52% of input dissolved total carbon (DTC), and the produced O2 simultaneously facilitated aerobic nitrification and P uptake with the coexisting phototrophs serving as a C fixer and O2 supplier. This resulted in a stably high total N removal of 81 ± 7% and an N assimilation rate of 7.55 mg/(g-MLVSS∙d) with enhanced microbial assimilation and simultaneous nitrification/denitrification. Good P removal of 92–98% was maintained during the test period at a molar ∆P/∆C ratio of 0.36 ± 0.03 and high P release and uptake rates of 10.84 ± 0.41 and 7.18 ± 0.24 mg/(g- MLVSS∙h), respectively. Photosynthetic O2 was more advantageous for N and P removal than mechanical aeration. This proposed system can contribute to a better design and sustainable operation of WWTPs using algal-bacterial AGS. [Display omitted]