Optimization of Dissolved Silica Removal from Reverse Osmosis Concentrate by Gedaniella flavovirens for Enhanced Water Recovery

Han Gao, Shinya Sato, Hitoshi Kodamatani, Takahiro Fujioka, Kenneth P. Ishida and Keisuke Ikehata ()
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Han Gao: Ingram School of Engineering, Texas State University, San Marcos, TX 78666, USA
Shinya Sato: Department of Marine Science and Technology, Fukui Prefectural University, Fukui 917-0003, Japan
Hitoshi Kodamatani: Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-8544, Japan
Takahiro Fujioka: Graduate School of Engineering, Nagasaki University, Nagasaki 852-8521, Japan
Kenneth P. Ishida: Orange County Water District, Fountain Valley, CA 92708, USA
Keisuke Ikehata: Ingram School of Engineering, Texas State University, San Marcos, TX 78666, USA

Sustainability, 2024, vol. 16, issue 10, 1-14

Abstract: Photobiological treatment of reverse osmosis concentrate (ROC) using brackish diatoms is a green and sustainable technology that can enhance water recovery by removing dissolved silica from ROC while producing beneficial biomass. This study aimed to determine the optimum conditions for the photobiological treatment of ROC obtained from a full-scale advanced water purification facility using Gedaniella flavovirens Psetr3. While light color presented minor impacts on the silica uptake rate, the impact of color intensity was significant. The uptake rate improved from 28 ± 1 to 48 ± 7 mg/L/day by increasing photosynthetically active radiation (PAR) from 50 to 310 µmol m −2 s −1 . Increasing the PAR further did not improve the performance. The optimum temperature was around 23–30 °C. While the silica uptake was slower at 10 °C, G. flavovirens Psetr3 was unable to survive at 40 °C. Experiments using sunlight as a light source verified the impact of temperature on the silica uptake and the detrimental effect of ultraviolet radiation on this diatom. The sunlight-based treatment effectively removed N -nitrosodimethylamine. The results of this study are being used in subsequent pilot-scale investigations and full-scale technoeconomic analysis and will contribute to the further development of this sustainable water technology.

Keywords: concentrate management; desalination; diatoms; green technology; nitrosamines; photobiological treatment; potable reuse; reverse osmosis; sustainable water resources (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2024
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