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Loh WH, Cai QQ, Li R, Jothinathan L, Lee BCY, Ng OH, Guo J, Ong SL, Hu JY. Reverse osmosis concentrate treatment by microbubble ozonation-biological activated carbon process: Organics removal performance and environmental impact assessment. Sci Total Environ 2021; 798:149289. [PMID: 34340085 DOI: 10.1016/j.scitotenv.2021.149289] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Revised: 07/22/2021] [Accepted: 07/23/2021] [Indexed: 06/13/2023]
Abstract
Reverse osmosis (RO) is being used in many water reclamation facilities to produce high quality water that can be reused for different purposes. As a part of the RO process, a reject stream is produced as the reverse osmosis concentrate (ROC), which contains elevated levels of contaminants compared to the source water. Effective treatment and safe disposal of ROC via cost-effective means is very challenging. This study aims to develop a robust microbubble ozonation-biological process for industrial ROC treatment with a target effluent chemical oxygen demand (COD) lower than 60 mg/L. As compared to macrobubble ozonation, microbubble ozonation exhibited better ozone dissolution and 29% higher COD removal efficiency with the same ozone dosage. Under the optimum operating conditions with ozone dosage of 30 mg/L, ROC natural pH of 8.67 and ozonation duration of 1 h, microbubble ozonation achieved 42% COD removal efficiency while increasing the BOD5/COD ratio (ratio of biological oxygen demand over 5 days to the corresponding chemical oxygen demand) in ROC from 0.042 to 0.216. A biological activated carbon (BAC) column with an empty bed contact time (EBCT) of 120 min was combined with microbubble ozonation for continuous ROC treatment. Over the 100-day operation, the combined system performed consistent organics removal with an average effluent COD of 45 mg/L. Both LC-OCD data and fluorescence EEM spectra confirmed humic substances were the dominant organic species in ROC. Ozone pre-treatment could achieve significant removal of humic substances in raw ROC. ATP analysis found that ozone pre-treatment enhanced BAC biofilm activity by around 5 folds. 5 min acute toxicity assessment with Aliivibrio fischeri showed 4 times reduction of bioluminescence inhibition in ozone treated ROC. From the environmental point of view, Life cycle assessment (LCA) results demonstrated that Ozone-BAC system had significant environmental burdens on climate change and human toxicity due to the electricity production process. These environmental impacts can be mitigated by optimizing the ozonation process with reduced ozone dosage or utilizing renewable energy sources for electricity generation.
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Affiliation(s)
- W H Loh
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore; Department of Civil & Environmental Engineering, Faculty of Engineering, National University of Singapore, Block E1A, #07-01, 1 Engineering Drive 2, 117576, Singapore
| | - Q Q Cai
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore; Department of Civil & Environmental Engineering, Faculty of Engineering, National University of Singapore, Block E1A, #07-01, 1 Engineering Drive 2, 117576, Singapore
| | - R Li
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore; Department of Civil & Environmental Engineering, Faculty of Engineering, National University of Singapore, Block E1A, #07-01, 1 Engineering Drive 2, 117576, Singapore
| | - L Jothinathan
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore; Department of Civil & Environmental Engineering, Faculty of Engineering, National University of Singapore, Block E1A, #07-01, 1 Engineering Drive 2, 117576, Singapore
| | - B C Y Lee
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore; Department of Civil & Environmental Engineering, Faculty of Engineering, National University of Singapore, Block E1A, #07-01, 1 Engineering Drive 2, 117576, Singapore
| | - O H Ng
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore
| | - J Guo
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore
| | - S L Ong
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore; Department of Civil & Environmental Engineering, Faculty of Engineering, National University of Singapore, Block E1A, #07-01, 1 Engineering Drive 2, 117576, Singapore
| | - J Y Hu
- National University of Singapore, Sembcorp-NUS Corporate Laboratory c/o FoE, Block E1A, #04-01, 1 Engineering Drive 2, 117576, Singapore; Department of Civil & Environmental Engineering, Faculty of Engineering, National University of Singapore, Block E1A, #07-01, 1 Engineering Drive 2, 117576, Singapore.
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Allam J, Sajjad MT, Sutton R, Litvinenko K, Wang Z, Siddique S, Yang QH, Loh WH, Brown T. Measurement of a reaction-diffusion crossover in exciton-exciton recombination inside carbon nanotubes using femtosecond optical absorption. Phys Rev Lett 2013; 111:197401. [PMID: 24266488 DOI: 10.1103/physrevlett.111.197401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 10/02/2013] [Indexed: 06/02/2023]
Abstract
Exciton-exciton recombination in isolated semiconducting single-walled carbon nanotubes was studied using femtosecond transient absorption. Under sufficient excitation to saturate the optical absorption, we observed an abrupt transition between reaction- and diffusion-limited kinetics, arising from reactions between incoherent localized excitons with a finite probability of ~0.2 per encounter. This represents the first experimental observation of a crossover between classical and critical kinetics in a 1D coalescing random walk, which is a paradigm for the study of nonequilibrium systems.
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Affiliation(s)
- J Allam
- Advanced Technology Institute and Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom
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Abstract
We propose and demonstrate hydrophobic photonic crystal fibers (PCFs). A chemical surface treatment for making PCFs hydrophobic is introduced. This repels water from the holes of PCFs, so that their optical properties remain unchanged even when they are immersed in water. The combination of a hollow core and a water-repellent inner surface of the hydrophobic PCF provides an ultracompact dissolved-gas sensor element, which is demonstrated for the sensing of dissolved ammonia gas.
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Affiliation(s)
- Limin Xiao
- Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK.
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Asimakis S, Petropoulos P, Poletti F, Leong JYY, Moore RC, Frampton KE, Feng X, Loh WH, Richardson DJ. Towards efficient and broadband four-wave-mixing using short-length dispersion tailored lead silicate holey fibers. Opt Express 2007; 15:596-601. [PMID: 19532280 DOI: 10.1364/oe.15.000596] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We demonstrate four-wave-mixing based wavelength conversion at 1.55 mum in a 2.2 m-long dispersion-shifted lead-silicate holey fiber. For a pump peak power of ~6 W, a conversion efficiency of -6 dB is achieved over a 3-dB bandwidth of ~30 nm. Numerical simulations are used to predict the performance of the fiber for different experimental conditions and to address the potential of dispersion-tailored lead silicate holey fibers in wavelength conversion applications utilizing four-wave-mixing. It is shown that highly efficient and broadband wavelength conversion, covering the entire C-band, can be achieved for such fibers at reasonable optical pump powers and for fiber lengths as short as ~2 m.
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Samson BN, Loh WH, de Sandro JP. Experimental evidence of differences in the absorption spectra of clustered and isolated ions in erbium-doped fibers. Opt Lett 1997; 22:1763-1765. [PMID: 18188358 DOI: 10.1364/ol.22.001763] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The absorption spectra of clustered and isolated ions in erbium-doped germanosilicate fibers have been experimentally studied. The ground-state absorption spectra broaden as the degree of erbium-ion clustering increases, indicating that the absorption spectrum of clustered ions is significantly different from that of the homogeneous ions. This fact is confirmed by comparison of the broadened absorption spectra with the fiber's unbleachable loss spectrum, a direct measurement of the clustered ions. This is the first experimental evidence to the authors' knowledge that indicates different absorption cross sections for the two species of ions in germanosilicate glass, an assumption that is used in the theoretical description of self-pulsing in erbium-doped fiber lasers but is in direct contradiction to the pair-induced quenching model widely used to characterize erbium-doped fiber amplifiers.
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Dong L, Loh WH, Caplen JE, Minelly JD, Hsu K, Reekie L. Efficient single-frequency fiber lasers with novel photosensitive Er/Yb optical fibers. Opt Lett 1997; 22:694-696. [PMID: 18185631 DOI: 10.1364/ol.22.000694] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Boron- and germanium-doped highly photosensitive cladding is used in a novel design to achieve photosensitive Er/Yb-doped fibers, permitting short, strong gratings (length approximately 1 cm, reflectivity >99%) to be written without hydrogenation. The high absorption at 980 nm in Er/Yb fibers permits efficient pump absorption over a short device length, which is ideal for achieving highly efficient single-frequency fiber lasers. Both single-frequency Bragg-grating reflector and distributed-feedback lasers with slope efficiencies of 25% with respect to launched pump power have been realized in such fibers.
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Affiliation(s)
- L Dong
- Optoelectronics Research Centre, The University of Southampton, Southampton SO17 1BJ, UK
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Kringlebotn JT, Loh WH, Laming RI. Polarimetric Er(3+)-doped fiber distributed-feedback laser sensor for differential pressure and force measurements. Opt Lett 1996; 21:1869-1871. [PMID: 19881829 DOI: 10.1364/ol.21.001869] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We propose and demonstrate a polarimetric Er(3+) -doped fiber distributed-feedback laser sensor in which a force applied transversely along the fiber laser induces a birefringence that gives rise to a change in the beat frequency between the two orthogonally polarized laser modes. We measure a sensitivity of ~9.6 GHzysNymmd, a wide dynamic range with stable two-mode operation for frequency separations up to 50 GHz, and high sensor resolution owing to the narrow beat frequency bandwidth of <10 kHz. The temperature sensitivity is dominated by the temperature dependence of the inherent birefringence, which was measured to be -130 kHz/ degrees C. The sensor permits independent pressure-force and temperature measurements.
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Cheng Y, Kringlebotn JT, Loh WH, Laming RI, Payne DN. Stable single-frequency traveling-wave fiber loop laser with integral saturable-absorber-based tracking narrow-band filter. Opt Lett 1995; 20:875-877. [PMID: 19859359 DOI: 10.1364/ol.20.000875] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We demonstrate stable single-frequency and polarization operation of a traveling-wave, Er(3+)-doped fiber loop laser by incorporating an unpumped Er(+3)-doped fiber section butted against a narrow-band feedback reflector. The saturable absorber acts as a narrow bandpass filter that automatically tracks the lasing wavelength, thus ensuring single-frequency operation. Output powers up to 6.2 mW at 1535 nm were obtained for launched pump powers of 175 mW at 1064 nm. At this output, the relative intensity noise was less than -112 dBy/Hz at frequencies above 200 kHz and a laser linewidth of less than 0.95 kHz, whereas the lasing frequency was observed to drift slowly (~170 MHz/h) because of environmental effects.
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Atkinson D, Loh WH, Afanasjev VV, Grudinin AB, Seeds AJ, Payne DN. Increased amplifier spacing in a soliton system with quantum-well saturable absorbers and spectral filtering. Opt Lett 1994; 19:1514-1516. [PMID: 19855568 DOI: 10.1364/ol.19.001514] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The spacing between optical amplifiers in a long-haul soliton system may be increased to 100 km by using only passive quantum-well saturable absorbers and narrow-band filters for soliton control. After transmission over 9000 km at 10 Gbits/s, the effects of soliton-soliton interaction and Gordon-Haus jitter in the proposed systemyield bit error rates of better than 10(-9).
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Abstract
Azospirillum brasilense Sp 7 grew rapidly in AZO medium containing reduced nitrogen and succinate as an energy source, with a doubling time of 43 min. No growth was measured with glucose as the sole carbon source. In contrast, Azospirillum lipoferum Sp 59b could grow in media containing either succinate or glucose with a doubling time of 69 min and 223 min, respectively. Warburg-Barcroft respirometry showed that the rate of oxygen consumption by A. brasilense Sp 7 on glucose medium (0.034 mumol of O2 min-1 mg-1 of cell protein) was only one-quarter of that on succinate medium (0.14 mumol of O2 min-1 mg-1). Radioisotopic labeling showed that very little glucose was assimilated by A. brasilense Sp 7 as compared to succinate. High respiration rates were measured on A. lipoferum Sp 59b with either succinate (0.15 mumol of O2 min-1 mg-1) or glucose (0.13 mumol of O2 min-1 mg-1) as the sole carbon source. The pattern of CO2 evolution from differentially labeled succinate indicated that A. brasilense Sp 7 had a complete tricarboxylic acid cycle. Assimilation of most of the radioactivity from labeled succinate, pyruvate, and acetate into lipids suggested a strong anabolic metabolism and the presence of an active malic enzyme of phosphoenolpyruvate carboxykinase. The distribution of radioactivity from differentially labeled pyruvate showed that gluconeogenesis competed with pyruvate dehydrogenase. Uptake and incorporation of labeled acetate also indicated the presence of a glyoxylate cycle in A. brasilense Sp 7.
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Hartsel SC, Loh WH, Robertson LW. Biotransformation of Cannabidiol to Cannabielsoin by Suspension Cultures of Cannabis sativa and Saccharum officinarum. Planta Med 1983; 48:17-9. [PMID: 17404934 DOI: 10.1055/s-2007-969870] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Suspension cultures of CANNABIS SATIVA L. and SACCHARUM OFFICINARUM L. have been shown to biotransform cannabidiol to Cannabielsoin under normal growth conditions. Both Cannabielsoin C-1 stereoisomers were produced. Mass spectral and chromatographic evidence were used in this identification. This is the first reported biologically catalyzed synthesis of Cannabielsoin as well as the first biotransformation of any cannabinoid by plant tissue culture systems. Possible mechanisms and significance of this conversion are discussed.
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Affiliation(s)
- S C Hartsel
- Department of Microbiology, The Ohio State University, Columbus, Ohio, U.S.A
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