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The exploration of monochromatic near-infrared LED improved anoxygenic photosynthetic bacteria Rhodopseudomonas sp. for wastewater treatment
Accepted Manuscript The exploration of monochromatic near-infrared LED improved anoxygenic photosynthetic bacteria Rhodopseudomonas sp. for wastewater treatment Xiang Qi, Yiwei Ren, Enling Tian, Xingzu Wang PII: DOI: Reference:
S0960-8524(17)30877-5 http://dx.doi.org/10.1016/j.biortech.2017.05.202 BITE 18228
To appear in:
Bioresource Technology
Received Date: Revised Date: Accepted Date:
23 April 2017 27 May 2017 30 May 2017
Please cite this article as: Qi, X., Ren, Y., Tian, E., Wang, X., The exploration of monochromatic near-infrared LED improved anoxygenic photosynthetic bacteria Rhodopseudomonas sp. for wastewater treatment, Bioresource Technology (2017), doi: http://dx.doi.org/10.1016/j.biortech.2017.05.202
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The exploration of monochromatic near-infrared LED improved anoxygenic photosynthetic bacteria Rhodopseudomonas sp. for wastewater treatment Xiang Qi a, b, Yiwei Ren a, c, Enling Tian a, Xingzu Wang a, * a
Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China b
College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 101407, China c
Chongqing Industrial Technology Innovation Institute of Environmental Protection Membrane Materials and Equipment Technology, Chongqing 408400, China
Abstract The future wastewater treatment requires high-efficiency and energy-saving technology. Anoxygenic photosynthetic bacteria (APB) is deemed as an eco-friendly microorganism, which could be employed in wastewater treatment. Here, monochromatic near-infrared (MNIR) light emitting diode (LED) was used, and three key factors (light quality, light intensity and photoperiod) of it were analyzed by a response surface methodology (RSM) in APB wastewater treatment. The results showed that light quality was the biggest impact factor in APB wastewater treatment, and nearly 58.07% of NH4+-N and 70.62% of chemical oxygen demand (COD) could be removed based on 46.4% of that theoretically possible. The light quality’s study revealed that APB had the highest NH4+-N and COD removal, biomass production, and bacteriochlorophyll a production with 850 nm IR LED. Moreover, the application of optimal MNIR LED could not only save energy, but also avoid algae bloom of photo-bioreactors (PBR). Keywords: Anoxygenic photosynthetic bacteria, Monochromatic near-infrared, LED, Wastewater treatment, Response surface methodology Highlights 1 / 20
· Different MNIR LEDs were used for APB wastewater treatment. · The highest nutrient removal was predicted by RSM. · Light quality was the biggest impact factor in APB wastewater treatment. · MNIR LED could not only save energy, but also avoid algae bloom of PBR.
1. Introduction Anoxygenic photosynthetic bacteria (APB) can live in different light environments, which include solar light, geothermal light, artificial light and so on. The direct reason is that APB can convert light energy into chemical energy to support their life cycle (Prachanurak et al., 2014). Purple nonsulfur bacteria is one of APB, which is metabolically diverse and can grow as photoheterotrophs, photoautotrophs or chemoheterotrophs-switching from one mode to another depending on conditions available (Larimer et al., 2004). The purple nonsulfur bacteria able to use light energy increases their organic matter utilization efficiency, which indicates a unique role of APB in the microbial degradation webs. Currently, APB have been widely used in many fields based on its characteristics, such as wastewater treatment, river bioremediation, new energy development, aquaculture production, medical fields and so on (Berman et al., 2014; Hallenbeck & Liu, 2016; Sasaki et al., 2005; Tamiaki et al., 2014). The treatment methods of high concentrated organic wastewater with APB, although widely studied, still present the challenges of inefficiency and energy-extensive consumption. Therefore, the treatment process of wastewater with APB need to be reformed from high-efficiency and energy-saving technology. Purple nonsulfur bacteria have two different pigment-protein complexes, and the core complex was consisted of one or two reaction centers, which include light-harvesting system and peripheral complex (Mascle-Allemand et al., 2010; Saikin et al., 2014). The reaction centers can promote the efficient conversion of light energy into ATP synthesis. Hence, the exploration of provocative light sources will become hotspot in APB wastewater treatment. The traditional incandescent lamp culture will be replaced by LED due to the short life time and high power consumption. The previous studies showed blue and red LED could promote the growth and wastewater treatment of APB effectively (Kuo et al., 2012; Qin et al., 2014b). The different LEDs improved APB wastewater treatment, although well studied, still present amounts of challenges. The main light-absorbing pigments of APB contain bacteriochlorophyll and carotenoid, which can absorb wide spectra from light resources. The absorption wavelength ranges of bacteriochlorophyll and carotenoid are 715nm-1050nm and 450nm-550nm, respectively (Beatty et al., 2005). Therefore, the electromagnetic wave, which is located in out of visible light, also can drive APB 2 / 20
photosynthesis based on that theoretically possible. Currently, some studies indicated that APB can carry out photosynthesis with monochromatic near-infrared (MNIR) (Glaeser & Overmann, 1999; Massé et al., 2002; Saikin et al., 2014). Although the studies had proved that MNIR could activate APB, the effects of optimal MNIR LED on APB wastewater treatment have not yet been reported. This study aimed to explore an optimal MNIR LED for APB wastewater treatment. Here, three key factors (light quality, light intensity and photoperiod) of IR LED were analyzed by a response surface methodology (RSM) in APB wastewater treatment. Moreover, the significance of this work could not only save energy, but also avoid algae bloom of photo-bioreactors (PBR). 2. Materials and analysis methods 2.1. Materials Rhodopseudomonas sp. strain was a strain obtained from the culture collection of the Key Laboratory of Reservoir Aquatic Environment, Chinese Academy of Sciences, China. The cells were cultured in a thermostat incubator (30°C) using the growth medium (RCVBN Medium) with an incandescent lamp of 40 W. After 72 h, the APB cells in exponential phase were used for wastewater treatment at a volume ratio of 1:50. The artificial wastewater was consisted of the improved medium, which (pH adjusted to 7.0–7.1) contained 3 g/L disodium succinate; 1 g/L NaHCO3; 1 g/L NH4Cl; 0.1 g/L yeast extract; 0.2 g/L KH2PO4; 0.1 g/L MgSO4; 1 mL/L microelement solution and 1 L distilled water. The microelement solution was comprised 0.2 g/L FeSO4·7H2O; 0.1 g/L MnCl2·4H2O; 0.1 g/L H3BO3; 0.1 g/L CoCl2·6H2O; 0.1 g/L ZnCl2; 0.02 g/L Na2MoO4·2H2O; 0.02 g/L NiCl2·6H2O; 0.01 g/L CuCl2·2H2O and 1 L distilled water. The artificial wastewater insured the initial nutrients with a chemical oxygen demand (COD) and NH4+-N of 4000 mg/L, 260 mg/L. 2.2. Methods The experiments were carried out in 100 mL serum bottles in this study, and 60 mL artificial wastewater was added to the anaerobic reactor. Light resources were provided by seventeen MNIR LED, which included four 760 nm MNIR LED, nine 850 nm MNIR LED and four 940 nm MNIR LED, respectively. The design of light quality was carried out based on the absorption wavelength of bacteriochlorophyll (Hartigan et al., 2002) and absorption spectra of intact cells of the purple non-sulfur bacterium (Stomp et al., 2007). The three key factors 3 / 20
(light quality, and light intensity and photoperiod) of IR LED were studied by RSM. The experimental design was displayed in Fig. 1. IR LED intensity was measured by IR power meter (LH-129A, China). The dissolved oxygen concentration (DO) could not exceed 0.5 mg/L. The absorption spectra of the whole cells were scanned by a UV-Vis spectrophotometer (Lambda 950, PerkinElmer, America) from 400 nm to 900 nm. 2.2.1. Analysis of water quality, biomass and bacteriochlorophyll a The analyzed parameters of water quality contained COD and NH4+-N, which were tested by APHA standard methods (Association & Washington, 1995). The biomass was obtained according to the traditional method (Jeswani & Mukherji, 2012). Bacteriochlorophyll a was extracted by acetone-methanol method (7:2 V/V). The supernatant of bacteria solution was removed by 9000 r/min for 10 min, and the precipitates were used to extract bacteriochlorophyll a by adding acetone-methanol solution. The samples would be measured with a UV-Vis spectrophotometer (UV-2550, Shimadzu, Japan) at a wavelength range of 400-900 nm, and the whole process was operated under a darkness condition. The contents of bacteriochlorophyll a were calculated by the Eqs. (1): Bacteriochlorophyll a content
(1)
Where was the absorbances of the extracts at 770 nm (bacteriochlorophyll a); was the extinction coefficient of bacteriochlorophyll a ( 0.076 Μm-1cm-1); was the path-length of the cuvette used in the spectrophotometer; and was the initial amount (g) of the cells divided by the final volume (mL) of extracts obtained (Qin et al., 2014b). All statistical analyses were performed using Origin 8.0® software, and three parallel results were conducted to ensure the accuracy of statistical analysis. Moreover, the thermal effect of IR was covered by thermostat incubator. 2.2.2. Optimization with RSM and energy cost assessment Design Expert 8.0® was used for a Box–Behnken experimental design, which was used to examine the key factors for the optimal IR LED and to analyze possible interactive effects of key parameters (Box & Behnken, 1960). The experimental design mainly analyzed the effects of light quality and intensity, light quality and photoperiod, and light intensity and photoperiod, on NH4+-N and COD removal. Box–Behnken design with three independent variables and two responses included 17 experimental runs in Table 1. Energy cost (EC) was defined as the energy usage charges per unit of 4 / 20
bacteria biomass in APB wastewater treatment, and it was calculated using Eqs. (2). The energy cost assessment (ECA) was proposed for a better comparison of energy usage charges with different light resources in APB wastewater treatment, as shown in the Eqs. (3). EC
(2)
ECA
(3)
Where was the power of light-emitter (W); was the operational time of light-emitter within a treatment cycle (h); was the corresponding charges per KWh; was the bacteria biomass production (mg/L); and were the energy-saving efficiency comparing with incandescent lamp (IL) in different study; and were the different light resources except for incandescent lamp (Aymerich et al., 2015). 3. Results and discussion 3.1. ANOVA analysis of NH4+-N and COD removal Box-Behnken experimental design with three independent variables (light intensity, light photoperiod and quality) and two responses (NH4+-N and COD removal). Light was necessary for the growth of APB and hence for NH4+-N and COD removal. ANOVA analysis revealed that the model for NH4+-N and COD removal were very significant (Table 2). The P-values of NH4+-N and COD removal were 0.0403 and 0.0033, which showed there were less chance of occurring due to noise. And the P-value less than 0.05 indicated model terms were significant. The DOE software predicted (light intensity)2, (light quality)2 to be significant model terms for NH4+-N removal, and light intensity, light quality, light photoperiod light quality, (light photoperiod)2, (light intensity)2, (light quality)2 to be significant model terms for COD removal. Moreover, non-significant lack of fit was good for NH4+-N and COD removal model, the results hoped that the model was fit. To sum up, the ANOVA values revealed that the experimental results were statistically significant. 3.2. Perturbation plot and response surface analysis of NH4+-N and COD removal The effect of key factors could be analyzed by perturbation plot, which showed the difference at one point in the design space. Thus the center point (light photoperiod: 20 min/10 min, light intensity: 4.25 W/m2, light quality: 850 nm) replicated 5 times, and 57±11% of NH4+-N and 70±7% of COD removal were 5 / 20
obtained. As Fig. 2 shows, NH4+-N and COD removal were most sensitive to the change of light quality (i.e. curve C is the steepest) away from the center point. The perturbation plot of COD removal (Fig. 2a) was more sensitive compare to NH4+-N removal (Fig. 2a). On the other hand, the NH4+-N and COD removal were least sensitive to the change of light intensity (curve B) and light photoperiod (curve A) away from the center point. Moreover, the perturbation plot of NH4+-N removal was different from COD removal for light intensity and light photoperiod, the possible explanation was that Rhodopseudomonas sp. consume nutrient substances with different rate at different conditions. In conclusion, this analysis showed that the actual removal optimum lay nearby 850 nm, with a predicted removal of 58.07% NH4+-N and 70.62% COD at 821 nm, 4.94 W/m2, 22 min/8 min. Response surface analysis aimed to analyze the possible interactive effects of key parameters on NH4+-N and COD removal. When light photoperiod and intensity vary at a medium light quality (850 nm), it can be observed that NH4+-N and COD removal are quite low at low light intensity and light photoperiod (Fig. 3a, d). NH4+-N and COD removal (nearby 60% and 70%) are the highest at the medium levels of light intensity and light photoperiod, which start to produce an interactive effect from the two-dimensional contour. Varying light quality and light photoperiod at a medium level of light intensity (4.25 W/m2) displayed amounts of interesting results for NH4+-N and COD removal (Fig. 3b, e). NH4+-N and COD removal are quite enhanced at high light photoperiod and intermediate level of light quality. The two-dimensional contour exhibited interaction between the two factors. In addition, somewhat effects (Fig. 3c, f), that are analogous to those aforementioned for light quality and light photoperiod, are observed when variations in light quality and light intensity at light photoperiod (20 min/10 min) are examined. NH4+-N and COD removal at high light quality are low unconsidered of the light intensity. The two-dimensional contour as well suggested that the factors interact for NH4+-N and COD removal. To sum up, the above results suggested that the actual removal optimum located in nearby 850 nm, with a predicted removal of 58.07% NH4+-N and 70.62% COD at 821 nm, 4.94 W/m2, 22 min/8 min. The pollution removal was significantly different from the previous studies (Qin et al., 2014a; Qin et al., 2014b; Yan et al., 2013), and the possible explanation was the use of different strains and wastewater. Moreover, this analysis also showed that NH4+-N and COD removal were particularly sensitive to the variation of light quality. Although it existed an interactive effect to the key parameters, the effects of light intensity and light photoperiod on NH4+-N and COD removal were frailer than light quality. At the same time, the study explored the effects of three parameters on NH4+-N and COD removal in one experimental model, it would provide a valuable reference for the future PBR design. Moreover, the study analyzed detailedly the 6 / 20
effects of light quality on NH4+-N and COD removal, biomass and bacteriochlorophyll a production in wastewater treatment based on the above results. 3.3. Effects of light quality on NH4+-N and COD removal, biomass and bacteriochlorophyll a production The NH4+-N and COD removal were influenced by the MNIR LED at a constant light intensity and light photoperiod, and an incandescent lamp (mixed wavelengths) and dark condition served as the control (Fig. 4a, b). The NH4+-N removal with 850 nm IR was obviously higher than that at other conditions from 24 to 120 h. The most significant difference was achieved at the 72nd h. But the gap between 850 nm IR and incandescent lamp started to disappear from 120 to 144 h, and the reason was that the growth of APB had arrived a period of saturation. The highest NH4+-N removal was achieved with 850nm IR at 144 h, and the corresponding removal efficiency was 57.24%. The NH4+-N removal efficiency was about 12% under darkness condition. The COD removal with 850nm IR was also higher than that at other conditions from 24 to 144 h, and the corresponding removal efficiency was 70.21%. However, the biggest gap at the 96th h was different from the NH4+-N removal. The possible explanation was that APB could consume different substances at different rate. The COD removal efficiency was approximately 24% under darkness condition. In conclusion, the COD and NH4+-N removal efficiency with 850nm IR were more obvious than 760, 940nm IR, and shorter hydraulic retention time (HRT) of wastewater treatment was needed for the 850 nm IR groups. The effects of light quality on biomass, bacteriochlorophyll a production were analyzed in APB wastewater treatment, and the results were displayed in Fig. 4c, d. The biomass production with 850 nm IR and incandescent lamp were far higher than the others (the groups with 760 nm, 940 nm, dark). The effects of light quality on biomass production greatest to least ranked in the following order: 850 nm IR > incandescent lamp > 760 nm IR > 940 nm IR > dark. The corresponding biomass production with 850 nm IR was 1625 mg/L, which was 42% higher than the biomass with 940 nm IR. Bacteriochlorophyll a is the main light-harvesting pigment of APB, which is crucial for capturing and transferring light energy into chemical energy for APB growth and metabolism. As Fig. 4d shows, bacteriochlorophyll a production with IR LED was higher than the incandescent lamp. The effects of light quality on bacteriochlorophyll a production greatest to least ranked in the following order: 850 nm IR > 760 nm IR > 940 nm IR > incandescent lamp > dark. The gaps of NH4+-N and COD removal, biomass production between 850 nm IR and incandescent lamp were weeny. However, 850 nm IR LED was 7 / 20
predominately considered as the optimal light quality in view of energy-saving and long-lasting. Life time would be extended when IR (1000 h) was design as IR LED (10,0000 h), which could save about 80% energy comparing with incandescent lamp. The effects of some light quality on APB had been studied in recent years, they included incandescent lamp, LED (red, yellow, blue, white, green), halogen lamp, and fluorescence lamp (Table 3). Lee et al. (2011) and Kuo et al. (2012) thought the optimum light source was blue LED by using different strains and culture medium. However, Qin et al. (2014b) indicated the optimum light source was red LED by using Rhodopseudomonas and sugar wastewater. The team considered that the difference might be caused by the cultivating conditions and the usage of different APB strains. The pollution removal, biomass and bacteriochlorophyll a production were lower than the previous studies in this study, and the main explanation was the different of APB strains and wastewater. Moreover, incandescent lamp as a key control also could explain the phenomenon. In addition, bacteriochlorophyll a production with NIR LED was far higher than incandescent lamp, the result was possibly related to the absorption spectrum of bacteriochlorophyll (715 nm-1050 nm). Although the previous studies also showed that red and blue LED could save energy comparing with incandescent lamp, the negative effects of algae on APB could not be avoided in the PBR. Therefore, this study also analyzed the effects of MNIR LED on whole cells absorbance and algae growth. 3.4. Effects of MNIR LED on whole cells absorbance and energy cost assessment The absorption spectra of whole cells of APB with different light quality was detected (Fig. 5a). The 760 nm and 850 nm IR treatment displayed absorbance peaks at 865 nm, 806 nm and 591 nm, and some shoulder peaks from 420 nm to 500 nm. These belong to the characteristic peaks of APB. However, the absorbance peak with 940 nm IR was different from the others at 850 nm to 900 nm. The possible explanation was that 940 nm IR stimulated light-harvesting complex (Fig. 1), and led to the skewing of absorbance peak (Glaeser & Overmann, 1999). The absorption spectra of the cells with 850 nm IR was higher than the others, and the effects of light quality on the absorption spectra greatest to least ranked in the following order: 850 nm IR > 760 nm IR > 940 nm IR > dark. Therefore, this study suggested that 850 nm IR was appropriate to APB wastewater treatment indirectly. The bacteria biomass was closely related to energy consumption in APB wastewater treatment, hence the energy cost could be calculated by the energy usage charges per unit of bacteria biomass. According to the descriptions, the energy-saving efficiency ( ) was 89% comparing with incandescent lamp (IL) in this study. At the same time, ECA could be evaluated based on incandescent 8 / 20
lamp as a control. Here the ECA was 1.13 between 850 nm IR LED ( =89%) and red LED ( =79%) from that information and the previous study (Qin et al., 2015). When ECA exceeded 1, the energy cost of APB wastewater treatment with 850 nm IR LED was lower than red LED. Therefore, 850 nm IR LED was fit for the future APB wastewater treatment. Moreover, the application of optimal MNIR LED could not only save energy, but also avoid algae bloom of PBR. The previous studies also showed that most angle could not absorb MNIR (Stomp et al., 2007). Thus, the application of optimal MNIR LED could avoid algae bloom of PBR. 4. Conclusions Here the effects of three key factors (light quality, light intensity and photoperiod) of NIR on APB wastewater treatment were demonstrated by RSM for the first time, and the results showed the pollution removal was particularly sensitive to the variation of light quality. The light quality’s study revealed that 850 nm IR LED could produce the highest NH4+-N and COD removal, whole cells absorption spectra, biomass and bacteriochlorophyll a production comparing with the others. In addition, the optimal MNIR LED used about 80% less energy than incandescent lamp in APB wastewater treatment. Acknowledgments This study was supported by the National Natural Science Foundation of China (No. 51008025, 51478452). References Association, C., Washington, D. 1995. APHA, A. P. H. A. : Standard methods for the examination of water and wastewater. American Physical Education Review, 24(9), 481-486. Aymerich, I., Rieger, L., Sobhani, R., Rosso, D., Corominas, L. 2015. The difference between energy consumption and energy cost: Modelling energy tariff structures for water resource recovery facilities. Water Research, 81, 113-123. Beatty, J.T., Overmann, J., Lince, M.T., Manske, A.K., Lang, A.S., Blankenship, R.E., Van Dover, C.L., Martinson, T.A., Plumley, F.G. 2005. An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent. Proceedings of the National Academy of Sciences, 102(26), 9306-9310. Berman, T., Yacobi, Y.Z., Eckert, W., Ostrovsky, I. 2014. Heterotrophic and anoxygenic photosynthetic bacteria, in: Zohary, T., Sukenik, A., Berman, T., Nishri, A. (Eds.), Lake Kinneret: Ecology and Management. Springer Netherlands, Dordrecht, pp. 259-271. Box, G.E.P., Behnken, D.W. 1960. Some new three level designs for the study of 9 / 20
quantitative variables. Technometrics, 2(4), 455-475. Glaeser, J., Overmann, J. 1999. Selective enrichment and characterization of Roseospirillum parvum, gen. nov. and sp. nov., a new purple nonsulfur bacterium with unusual light absorption properties. Archives of Microbiology, 171(6), 405-416. Hallenbeck, P.C., Liu, Y. 2016. Recent advances in hydrogen production by photosynthetic bacteria. International Journal of Hydrogen Energy, 41(7), 4446-4454. Hartigan, N., Tharia, H.A., Sweeney, F., Lawless, A.M., Papiz, M.Z. 2002. The 7.5-Å electron density and spectroscopic properties of a novel low-light B800 LH2 from Rhodopseudomonas palustris. Biophysical Journal, 82(2), 963-977. Jeswani, H., Mukherji, S. 2012. Degradation of phenolics, nitrogen-heterocyclics and polynuclear aromatic hydrocarbons in a rotating biological contactor. Bioresource Technology, 111(1), 12-20. Kuo, F.S., Chien, Y.H., Chen, C.J. 2012. Effects of light sources on growth and carotenoid content of photosynthetic bacteria Rhodopseudomonas palustris. Bioresource Technology, 113(4), 315-318. Larimer, F.W., Chain, P., Hauser, L., Lamerdin, J., Malfatti, S., Do, L., Land, M.L., Pelletier, D.A., Beatty, J.T., Lang, A.S. 2004. Complete genome sequence of the metabolically versatile photosynthetic bacterium Rhodopseudomonas palustris. Nature Biotechnology, 22(1), 55-61. Lee, H.J., Park, J.-Y., Han, C.-H., Chang, S.-T., Kim, Y.-H., Min, J. 2011. Blue LED and succinic acid enhance the growth of Rhodobacter sphaeroides. World Journal of Microbiology and Biotechnology, 27(1), 189-192. Mascle-Allemand, C., Duquesne, K., Lebrun, R., Scheuring, S., Sturgis, J.N. 2010. Antenna mixing in photosynthetic membranes from Phaeospirillum molischianum. Proceedings of the National Academy of Sciences, 107(12), 5357-5362. Massé, A., Pringault, O., De, W.R. 2002. Experimental study of interactions between purple and green sulfur bacteria in sandy sediments exposed to illumination deprived of near-infrared wavelengths. Applied and Environmental Microbiology, 68(6), 2972-2981. Prachanurak, P., Chiemchaisri, C., Chiemchaisri, W., Yamamotob, K. 2014. Biomass production from fermented starch wastewater in photo-bioreactor with internal overflow recirculation. Bioresource Technology, 165(8), 129-136. Qin, Z., Zhang, P., Zhang, G. 2014a. Biomass and carotenoid production in photosynthetic bacteria wastewater treatment: Effects of light intensity. Bioresource Technology, 171, 330-335. Qin, Z., Zhang, P., Zhang, G. 2015. Biomass and pigments production in photosynthetic bacteria wastewater treatment: Effects of light photoperiod. Bioresource Technology, 190, 196-200. Qin, Z., Zhang, P., Zhang, G. 2014b. Biomass and pigments production in photosynthetic bacteria wastewater treatment: Effects of light sources. Bioresource Technology, 179, 505-509. Saikin, S.K., Khin, Y., Huh, J., Hannout, M., Wang, Y., Zare, F., Aspuruguzik, A., Tang, K.H. 2014. Chromatic acclimation and population dynamics of green sulfur bacteria 10 / 20
grown with spectrally tailored light. Scientific Reports, 4(3), 5057. Sasaki, K., Watanabe, M., Suda, Y., Ishizuka, A., Noparatnaraporn, N. 2005. Applications of photosynthetic bacteria for medical fields. Journal of Bioscience & Bioengineering, 100(5), 481-488. Stomp, M., Huisman, J., Stal, L.J., Matthijs, H.C.P. 2007. Colorful niches of phototrophic microorganisms shaped by vibrations of the water molecule. ISME J, 1(4), 271-282. Tamiaki, H., Matsunaga, S., Taira, Y., Wada, A., Kinoshita, Y., Kunieda, M. 2014. Synthesis of zinc 20-substituted bacteriochlorophyll-d analogs and their self-aggregation. Tetrahedron Letters, 55(22), 3351-3354. Yan, C., Luo, X., Zheng, Z. 2013. Effects of various LED light qualities and light intensity supply strategies on purification of slurry from anaerobic digestion process by Chlorella vulgaris. International Biodeterioration & Biodegradation, 79, 81-87.
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Fig. 1. Schematic diagram of experimental design.
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Fig. 2. Perturbation plot analysis of the effects of light intensity, light photoperiod and quality on NH4+-N removal (a) and COD removal (b). Design Expert 8.0® was used to form the perturbation. (A) light photoperiod; (B) light intensity; (C) light quality.
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Fig. 3. Response surface analysis of the interactive effects of key parameters on NH4+-N and COD removal. The response of NH4+-N and COD removal to different light intensity and light photoperiod at a constant light quality of 850 nm (a, d). The response of NH4+-N and COD removal to different light quality and light photoperiod at a constant light intensity of 4.25 W/m2 (b, e). The response of NH4+-N and COD removal to different light quality and light intensity at a constant light photoperiod of 20 min/10 min (c, f).
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Fig. 4. Effects of light quality (MNIR LED) on NH4+-N and COD removal (a, b), biomass and bacteriochlorophyll a production (c, d) in APB wastewater treatment.
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Fig. 5. Effects of MNIR LED on whole cells absorbance.
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Table 1 Box–Behnken experimental design with three independent variables and two responses. Run No.
Factor 1 C: light photoperiod a) (min)
Factor 2 B: light intensity b) (W/m 2)
Factor 3 A: light quality (nm)
Response 1 NH3-N removal (%)
Response 2 COD removal (%)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
25/5 15/15 20/10 20/10 25/5 20/10 15/15 20/10 25/5 15/15 20/10 20/10 20/10 20/10 25/5 15/15 20/10
4.25 4.25 4.25 8 0.5 4.25 8 4.25 8 0.5 0.5 0.5 4.25 4.25 4.25 4.25 8
760 760 850 940 850 850 850 850 850 850 760 940 850 850 940 940 760
52.51 38.59 52.51 35.25 43.16 57.78 41.97 60.42 46.35 38.11 40.75 29.43 46.02 68.33 32.34 37.56 42.84
64.55 46.85 65.84 45.89 53.62 67.13 53.6 69.06 63.91 50.38 51.02 37.54 61.33 77.28 41.52 46.51 60.04
Note: a) The photoperiod was designed to the light/dark (L/D) cycle, and 48 times every day (Qin et al., 2015). b) The light intensity was studied base on the surface area of the serum bottles.
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Table 2 ANOVA analysis response surface quadratic model. Removal
Source
F-Value
P-Value
Result
NH4+-N
Model Lack of Fit Model Lack of Fit
4.01 3.860E-003 9.78 0.041
0.0403 0.9996 0.0033 0.9873
significant not significant significant not significant
COD
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Table 3 Effects of light sources on APB growth as reported in the literature. PSB strains
Culture medium
Light sources
Optimum
References
Rhodopseudomona s
Sugar wastewate r
Red, yellow, blue, white LED and incandescent lamp
Red LED a)
(Qin et al., 2014b)
Cba. tepidum
Unknown
700 nm, 750 nm, 780 nm, 800 nm, 850 nm, 940 nm LED
800 nm LED
(Saikin et al., 2014)
b)
R. palustris
NS medium
Incandescent lamp, halogen lamp, fluorescence lamp, and white, yellow, red, blue and green LED
Blue LED a)
(Kuo et al., 2012)
R. sphaeroids
Sistrom’s minimal medium
Blue, green, red, white LED, fluorescent lamp
Blue LED b)
(Lee et al., 2011)
Rhodopseudomona s
Improved medium
850 nm LED
This study
760 nm, 850 nm, 940 nm NIR LED, Incandescent lamp Note: a) Biomass production; b) Growth rate.
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a)
Highlights
· Different MNIR LEDs were used for APB wastewater treatment. · The highest nutrient removal was predicted by RSM. · Light quality was the biggest impact factor in APB wastewater treatment. · MNIR LED could not only save energy, but also avoid algae bloom of PBR.
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S0960-8524(17)30877-5 http://dx.doi.org/10.1016/j.biortech.2017.05.202 BITE 18228
To appear in:
Bioresource Technology
Received Date: Revised Date: Accepted Date:
23 April 2017 27 May 2017 30 May 2017
Please cite this article as: Qi, X., Ren, Y., Tian, E., Wang, X., The exploration of monochromatic near-infrared LED improved anoxygenic photosynthetic bacteria Rhodopseudomonas sp. for wastewater treatment, Bioresource Technology (2017), doi: http://dx.doi.org/10.1016/j.biortech.2017.05.202
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The exploration of monochromatic near-infrared LED improved anoxygenic photosynthetic bacteria Rhodopseudomonas sp. for wastewater treatment Xiang Qi a, b, Yiwei Ren a, c, Enling Tian a, Xingzu Wang a, * a
Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China b
College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 101407, China c
Chongqing Industrial Technology Innovation Institute of Environmental Protection Membrane Materials and Equipment Technology, Chongqing 408400, China
Abstract The future wastewater treatment requires high-efficiency and energy-saving technology. Anoxygenic photosynthetic bacteria (APB) is deemed as an eco-friendly microorganism, which could be employed in wastewater treatment. Here, monochromatic near-infrared (MNIR) light emitting diode (LED) was used, and three key factors (light quality, light intensity and photoperiod) of it were analyzed by a response surface methodology (RSM) in APB wastewater treatment. The results showed that light quality was the biggest impact factor in APB wastewater treatment, and nearly 58.07% of NH4+-N and 70.62% of chemical oxygen demand (COD) could be removed based on 46.4% of that theoretically possible. The light quality’s study revealed that APB had the highest NH4+-N and COD removal, biomass production, and bacteriochlorophyll a production with 850 nm IR LED. Moreover, the application of optimal MNIR LED could not only save energy, but also avoid algae bloom of photo-bioreactors (PBR). Keywords: Anoxygenic photosynthetic bacteria, Monochromatic near-infrared, LED, Wastewater treatment, Response surface methodology Highlights 1 / 20
· Different MNIR LEDs were used for APB wastewater treatment. · The highest nutrient removal was predicted by RSM. · Light quality was the biggest impact factor in APB wastewater treatment. · MNIR LED could not only save energy, but also avoid algae bloom of PBR.
1. Introduction Anoxygenic photosynthetic bacteria (APB) can live in different light environments, which include solar light, geothermal light, artificial light and so on. The direct reason is that APB can convert light energy into chemical energy to support their life cycle (Prachanurak et al., 2014). Purple nonsulfur bacteria is one of APB, which is metabolically diverse and can grow as photoheterotrophs, photoautotrophs or chemoheterotrophs-switching from one mode to another depending on conditions available (Larimer et al., 2004). The purple nonsulfur bacteria able to use light energy increases their organic matter utilization efficiency, which indicates a unique role of APB in the microbial degradation webs. Currently, APB have been widely used in many fields based on its characteristics, such as wastewater treatment, river bioremediation, new energy development, aquaculture production, medical fields and so on (Berman et al., 2014; Hallenbeck & Liu, 2016; Sasaki et al., 2005; Tamiaki et al., 2014). The treatment methods of high concentrated organic wastewater with APB, although widely studied, still present the challenges of inefficiency and energy-extensive consumption. Therefore, the treatment process of wastewater with APB need to be reformed from high-efficiency and energy-saving technology. Purple nonsulfur bacteria have two different pigment-protein complexes, and the core complex was consisted of one or two reaction centers, which include light-harvesting system and peripheral complex (Mascle-Allemand et al., 2010; Saikin et al., 2014). The reaction centers can promote the efficient conversion of light energy into ATP synthesis. Hence, the exploration of provocative light sources will become hotspot in APB wastewater treatment. The traditional incandescent lamp culture will be replaced by LED due to the short life time and high power consumption. The previous studies showed blue and red LED could promote the growth and wastewater treatment of APB effectively (Kuo et al., 2012; Qin et al., 2014b). The different LEDs improved APB wastewater treatment, although well studied, still present amounts of challenges. The main light-absorbing pigments of APB contain bacteriochlorophyll and carotenoid, which can absorb wide spectra from light resources. The absorption wavelength ranges of bacteriochlorophyll and carotenoid are 715nm-1050nm and 450nm-550nm, respectively (Beatty et al., 2005). Therefore, the electromagnetic wave, which is located in out of visible light, also can drive APB 2 / 20
photosynthesis based on that theoretically possible. Currently, some studies indicated that APB can carry out photosynthesis with monochromatic near-infrared (MNIR) (Glaeser & Overmann, 1999; Massé et al., 2002; Saikin et al., 2014). Although the studies had proved that MNIR could activate APB, the effects of optimal MNIR LED on APB wastewater treatment have not yet been reported. This study aimed to explore an optimal MNIR LED for APB wastewater treatment. Here, three key factors (light quality, light intensity and photoperiod) of IR LED were analyzed by a response surface methodology (RSM) in APB wastewater treatment. Moreover, the significance of this work could not only save energy, but also avoid algae bloom of photo-bioreactors (PBR). 2. Materials and analysis methods 2.1. Materials Rhodopseudomonas sp. strain was a strain obtained from the culture collection of the Key Laboratory of Reservoir Aquatic Environment, Chinese Academy of Sciences, China. The cells were cultured in a thermostat incubator (30°C) using the growth medium (RCVBN Medium) with an incandescent lamp of 40 W. After 72 h, the APB cells in exponential phase were used for wastewater treatment at a volume ratio of 1:50. The artificial wastewater was consisted of the improved medium, which (pH adjusted to 7.0–7.1) contained 3 g/L disodium succinate; 1 g/L NaHCO3; 1 g/L NH4Cl; 0.1 g/L yeast extract; 0.2 g/L KH2PO4; 0.1 g/L MgSO4; 1 mL/L microelement solution and 1 L distilled water. The microelement solution was comprised 0.2 g/L FeSO4·7H2O; 0.1 g/L MnCl2·4H2O; 0.1 g/L H3BO3; 0.1 g/L CoCl2·6H2O; 0.1 g/L ZnCl2; 0.02 g/L Na2MoO4·2H2O; 0.02 g/L NiCl2·6H2O; 0.01 g/L CuCl2·2H2O and 1 L distilled water. The artificial wastewater insured the initial nutrients with a chemical oxygen demand (COD) and NH4+-N of 4000 mg/L, 260 mg/L. 2.2. Methods The experiments were carried out in 100 mL serum bottles in this study, and 60 mL artificial wastewater was added to the anaerobic reactor. Light resources were provided by seventeen MNIR LED, which included four 760 nm MNIR LED, nine 850 nm MNIR LED and four 940 nm MNIR LED, respectively. The design of light quality was carried out based on the absorption wavelength of bacteriochlorophyll (Hartigan et al., 2002) and absorption spectra of intact cells of the purple non-sulfur bacterium (Stomp et al., 2007). The three key factors 3 / 20
(light quality, and light intensity and photoperiod) of IR LED were studied by RSM. The experimental design was displayed in Fig. 1. IR LED intensity was measured by IR power meter (LH-129A, China). The dissolved oxygen concentration (DO) could not exceed 0.5 mg/L. The absorption spectra of the whole cells were scanned by a UV-Vis spectrophotometer (Lambda 950, PerkinElmer, America) from 400 nm to 900 nm. 2.2.1. Analysis of water quality, biomass and bacteriochlorophyll a The analyzed parameters of water quality contained COD and NH4+-N, which were tested by APHA standard methods (Association & Washington, 1995). The biomass was obtained according to the traditional method (Jeswani & Mukherji, 2012). Bacteriochlorophyll a was extracted by acetone-methanol method (7:2 V/V). The supernatant of bacteria solution was removed by 9000 r/min for 10 min, and the precipitates were used to extract bacteriochlorophyll a by adding acetone-methanol solution. The samples would be measured with a UV-Vis spectrophotometer (UV-2550, Shimadzu, Japan) at a wavelength range of 400-900 nm, and the whole process was operated under a darkness condition. The contents of bacteriochlorophyll a were calculated by the Eqs. (1): Bacteriochlorophyll a content
(1)
Where was the absorbances of the extracts at 770 nm (bacteriochlorophyll a); was the extinction coefficient of bacteriochlorophyll a ( 0.076 Μm-1cm-1); was the path-length of the cuvette used in the spectrophotometer; and was the initial amount (g) of the cells divided by the final volume (mL) of extracts obtained (Qin et al., 2014b). All statistical analyses were performed using Origin 8.0® software, and three parallel results were conducted to ensure the accuracy of statistical analysis. Moreover, the thermal effect of IR was covered by thermostat incubator. 2.2.2. Optimization with RSM and energy cost assessment Design Expert 8.0® was used for a Box–Behnken experimental design, which was used to examine the key factors for the optimal IR LED and to analyze possible interactive effects of key parameters (Box & Behnken, 1960). The experimental design mainly analyzed the effects of light quality and intensity, light quality and photoperiod, and light intensity and photoperiod, on NH4+-N and COD removal. Box–Behnken design with three independent variables and two responses included 17 experimental runs in Table 1. Energy cost (EC) was defined as the energy usage charges per unit of 4 / 20
bacteria biomass in APB wastewater treatment, and it was calculated using Eqs. (2). The energy cost assessment (ECA) was proposed for a better comparison of energy usage charges with different light resources in APB wastewater treatment, as shown in the Eqs. (3). EC
(2)
ECA
(3)
Where was the power of light-emitter (W); was the operational time of light-emitter within a treatment cycle (h); was the corresponding charges per KWh; was the bacteria biomass production (mg/L); and were the energy-saving efficiency comparing with incandescent lamp (IL) in different study; and were the different light resources except for incandescent lamp (Aymerich et al., 2015). 3. Results and discussion 3.1. ANOVA analysis of NH4+-N and COD removal Box-Behnken experimental design with three independent variables (light intensity, light photoperiod and quality) and two responses (NH4+-N and COD removal). Light was necessary for the growth of APB and hence for NH4+-N and COD removal. ANOVA analysis revealed that the model for NH4+-N and COD removal were very significant (Table 2). The P-values of NH4+-N and COD removal were 0.0403 and 0.0033, which showed there were less chance of occurring due to noise. And the P-value less than 0.05 indicated model terms were significant. The DOE software predicted (light intensity)2, (light quality)2 to be significant model terms for NH4+-N removal, and light intensity, light quality, light photoperiod light quality, (light photoperiod)2, (light intensity)2, (light quality)2 to be significant model terms for COD removal. Moreover, non-significant lack of fit was good for NH4+-N and COD removal model, the results hoped that the model was fit. To sum up, the ANOVA values revealed that the experimental results were statistically significant. 3.2. Perturbation plot and response surface analysis of NH4+-N and COD removal The effect of key factors could be analyzed by perturbation plot, which showed the difference at one point in the design space. Thus the center point (light photoperiod: 20 min/10 min, light intensity: 4.25 W/m2, light quality: 850 nm) replicated 5 times, and 57±11% of NH4+-N and 70±7% of COD removal were 5 / 20
obtained. As Fig. 2 shows, NH4+-N and COD removal were most sensitive to the change of light quality (i.e. curve C is the steepest) away from the center point. The perturbation plot of COD removal (Fig. 2a) was more sensitive compare to NH4+-N removal (Fig. 2a). On the other hand, the NH4+-N and COD removal were least sensitive to the change of light intensity (curve B) and light photoperiod (curve A) away from the center point. Moreover, the perturbation plot of NH4+-N removal was different from COD removal for light intensity and light photoperiod, the possible explanation was that Rhodopseudomonas sp. consume nutrient substances with different rate at different conditions. In conclusion, this analysis showed that the actual removal optimum lay nearby 850 nm, with a predicted removal of 58.07% NH4+-N and 70.62% COD at 821 nm, 4.94 W/m2, 22 min/8 min. Response surface analysis aimed to analyze the possible interactive effects of key parameters on NH4+-N and COD removal. When light photoperiod and intensity vary at a medium light quality (850 nm), it can be observed that NH4+-N and COD removal are quite low at low light intensity and light photoperiod (Fig. 3a, d). NH4+-N and COD removal (nearby 60% and 70%) are the highest at the medium levels of light intensity and light photoperiod, which start to produce an interactive effect from the two-dimensional contour. Varying light quality and light photoperiod at a medium level of light intensity (4.25 W/m2) displayed amounts of interesting results for NH4+-N and COD removal (Fig. 3b, e). NH4+-N and COD removal are quite enhanced at high light photoperiod and intermediate level of light quality. The two-dimensional contour exhibited interaction between the two factors. In addition, somewhat effects (Fig. 3c, f), that are analogous to those aforementioned for light quality and light photoperiod, are observed when variations in light quality and light intensity at light photoperiod (20 min/10 min) are examined. NH4+-N and COD removal at high light quality are low unconsidered of the light intensity. The two-dimensional contour as well suggested that the factors interact for NH4+-N and COD removal. To sum up, the above results suggested that the actual removal optimum located in nearby 850 nm, with a predicted removal of 58.07% NH4+-N and 70.62% COD at 821 nm, 4.94 W/m2, 22 min/8 min. The pollution removal was significantly different from the previous studies (Qin et al., 2014a; Qin et al., 2014b; Yan et al., 2013), and the possible explanation was the use of different strains and wastewater. Moreover, this analysis also showed that NH4+-N and COD removal were particularly sensitive to the variation of light quality. Although it existed an interactive effect to the key parameters, the effects of light intensity and light photoperiod on NH4+-N and COD removal were frailer than light quality. At the same time, the study explored the effects of three parameters on NH4+-N and COD removal in one experimental model, it would provide a valuable reference for the future PBR design. Moreover, the study analyzed detailedly the 6 / 20
effects of light quality on NH4+-N and COD removal, biomass and bacteriochlorophyll a production in wastewater treatment based on the above results. 3.3. Effects of light quality on NH4+-N and COD removal, biomass and bacteriochlorophyll a production The NH4+-N and COD removal were influenced by the MNIR LED at a constant light intensity and light photoperiod, and an incandescent lamp (mixed wavelengths) and dark condition served as the control (Fig. 4a, b). The NH4+-N removal with 850 nm IR was obviously higher than that at other conditions from 24 to 120 h. The most significant difference was achieved at the 72nd h. But the gap between 850 nm IR and incandescent lamp started to disappear from 120 to 144 h, and the reason was that the growth of APB had arrived a period of saturation. The highest NH4+-N removal was achieved with 850nm IR at 144 h, and the corresponding removal efficiency was 57.24%. The NH4+-N removal efficiency was about 12% under darkness condition. The COD removal with 850nm IR was also higher than that at other conditions from 24 to 144 h, and the corresponding removal efficiency was 70.21%. However, the biggest gap at the 96th h was different from the NH4+-N removal. The possible explanation was that APB could consume different substances at different rate. The COD removal efficiency was approximately 24% under darkness condition. In conclusion, the COD and NH4+-N removal efficiency with 850nm IR were more obvious than 760, 940nm IR, and shorter hydraulic retention time (HRT) of wastewater treatment was needed for the 850 nm IR groups. The effects of light quality on biomass, bacteriochlorophyll a production were analyzed in APB wastewater treatment, and the results were displayed in Fig. 4c, d. The biomass production with 850 nm IR and incandescent lamp were far higher than the others (the groups with 760 nm, 940 nm, dark). The effects of light quality on biomass production greatest to least ranked in the following order: 850 nm IR > incandescent lamp > 760 nm IR > 940 nm IR > dark. The corresponding biomass production with 850 nm IR was 1625 mg/L, which was 42% higher than the biomass with 940 nm IR. Bacteriochlorophyll a is the main light-harvesting pigment of APB, which is crucial for capturing and transferring light energy into chemical energy for APB growth and metabolism. As Fig. 4d shows, bacteriochlorophyll a production with IR LED was higher than the incandescent lamp. The effects of light quality on bacteriochlorophyll a production greatest to least ranked in the following order: 850 nm IR > 760 nm IR > 940 nm IR > incandescent lamp > dark. The gaps of NH4+-N and COD removal, biomass production between 850 nm IR and incandescent lamp were weeny. However, 850 nm IR LED was 7 / 20
predominately considered as the optimal light quality in view of energy-saving and long-lasting. Life time would be extended when IR (1000 h) was design as IR LED (10,0000 h), which could save about 80% energy comparing with incandescent lamp. The effects of some light quality on APB had been studied in recent years, they included incandescent lamp, LED (red, yellow, blue, white, green), halogen lamp, and fluorescence lamp (Table 3). Lee et al. (2011) and Kuo et al. (2012) thought the optimum light source was blue LED by using different strains and culture medium. However, Qin et al. (2014b) indicated the optimum light source was red LED by using Rhodopseudomonas and sugar wastewater. The team considered that the difference might be caused by the cultivating conditions and the usage of different APB strains. The pollution removal, biomass and bacteriochlorophyll a production were lower than the previous studies in this study, and the main explanation was the different of APB strains and wastewater. Moreover, incandescent lamp as a key control also could explain the phenomenon. In addition, bacteriochlorophyll a production with NIR LED was far higher than incandescent lamp, the result was possibly related to the absorption spectrum of bacteriochlorophyll (715 nm-1050 nm). Although the previous studies also showed that red and blue LED could save energy comparing with incandescent lamp, the negative effects of algae on APB could not be avoided in the PBR. Therefore, this study also analyzed the effects of MNIR LED on whole cells absorbance and algae growth. 3.4. Effects of MNIR LED on whole cells absorbance and energy cost assessment The absorption spectra of whole cells of APB with different light quality was detected (Fig. 5a). The 760 nm and 850 nm IR treatment displayed absorbance peaks at 865 nm, 806 nm and 591 nm, and some shoulder peaks from 420 nm to 500 nm. These belong to the characteristic peaks of APB. However, the absorbance peak with 940 nm IR was different from the others at 850 nm to 900 nm. The possible explanation was that 940 nm IR stimulated light-harvesting complex (Fig. 1), and led to the skewing of absorbance peak (Glaeser & Overmann, 1999). The absorption spectra of the cells with 850 nm IR was higher than the others, and the effects of light quality on the absorption spectra greatest to least ranked in the following order: 850 nm IR > 760 nm IR > 940 nm IR > dark. Therefore, this study suggested that 850 nm IR was appropriate to APB wastewater treatment indirectly. The bacteria biomass was closely related to energy consumption in APB wastewater treatment, hence the energy cost could be calculated by the energy usage charges per unit of bacteria biomass. According to the descriptions, the energy-saving efficiency ( ) was 89% comparing with incandescent lamp (IL) in this study. At the same time, ECA could be evaluated based on incandescent 8 / 20
lamp as a control. Here the ECA was 1.13 between 850 nm IR LED ( =89%) and red LED ( =79%) from that information and the previous study (Qin et al., 2015). When ECA exceeded 1, the energy cost of APB wastewater treatment with 850 nm IR LED was lower than red LED. Therefore, 850 nm IR LED was fit for the future APB wastewater treatment. Moreover, the application of optimal MNIR LED could not only save energy, but also avoid algae bloom of PBR. The previous studies also showed that most angle could not absorb MNIR (Stomp et al., 2007). Thus, the application of optimal MNIR LED could avoid algae bloom of PBR. 4. Conclusions Here the effects of three key factors (light quality, light intensity and photoperiod) of NIR on APB wastewater treatment were demonstrated by RSM for the first time, and the results showed the pollution removal was particularly sensitive to the variation of light quality. The light quality’s study revealed that 850 nm IR LED could produce the highest NH4+-N and COD removal, whole cells absorption spectra, biomass and bacteriochlorophyll a production comparing with the others. In addition, the optimal MNIR LED used about 80% less energy than incandescent lamp in APB wastewater treatment. Acknowledgments This study was supported by the National Natural Science Foundation of China (No. 51008025, 51478452). References Association, C., Washington, D. 1995. APHA, A. P. H. A. : Standard methods for the examination of water and wastewater. American Physical Education Review, 24(9), 481-486. Aymerich, I., Rieger, L., Sobhani, R., Rosso, D., Corominas, L. 2015. The difference between energy consumption and energy cost: Modelling energy tariff structures for water resource recovery facilities. Water Research, 81, 113-123. Beatty, J.T., Overmann, J., Lince, M.T., Manske, A.K., Lang, A.S., Blankenship, R.E., Van Dover, C.L., Martinson, T.A., Plumley, F.G. 2005. An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent. Proceedings of the National Academy of Sciences, 102(26), 9306-9310. Berman, T., Yacobi, Y.Z., Eckert, W., Ostrovsky, I. 2014. Heterotrophic and anoxygenic photosynthetic bacteria, in: Zohary, T., Sukenik, A., Berman, T., Nishri, A. (Eds.), Lake Kinneret: Ecology and Management. Springer Netherlands, Dordrecht, pp. 259-271. Box, G.E.P., Behnken, D.W. 1960. Some new three level designs for the study of 9 / 20
quantitative variables. Technometrics, 2(4), 455-475. Glaeser, J., Overmann, J. 1999. Selective enrichment and characterization of Roseospirillum parvum, gen. nov. and sp. nov., a new purple nonsulfur bacterium with unusual light absorption properties. Archives of Microbiology, 171(6), 405-416. Hallenbeck, P.C., Liu, Y. 2016. Recent advances in hydrogen production by photosynthetic bacteria. International Journal of Hydrogen Energy, 41(7), 4446-4454. Hartigan, N., Tharia, H.A., Sweeney, F., Lawless, A.M., Papiz, M.Z. 2002. The 7.5-Å electron density and spectroscopic properties of a novel low-light B800 LH2 from Rhodopseudomonas palustris. Biophysical Journal, 82(2), 963-977. Jeswani, H., Mukherji, S. 2012. Degradation of phenolics, nitrogen-heterocyclics and polynuclear aromatic hydrocarbons in a rotating biological contactor. Bioresource Technology, 111(1), 12-20. Kuo, F.S., Chien, Y.H., Chen, C.J. 2012. Effects of light sources on growth and carotenoid content of photosynthetic bacteria Rhodopseudomonas palustris. Bioresource Technology, 113(4), 315-318. Larimer, F.W., Chain, P., Hauser, L., Lamerdin, J., Malfatti, S., Do, L., Land, M.L., Pelletier, D.A., Beatty, J.T., Lang, A.S. 2004. Complete genome sequence of the metabolically versatile photosynthetic bacterium Rhodopseudomonas palustris. Nature Biotechnology, 22(1), 55-61. Lee, H.J., Park, J.-Y., Han, C.-H., Chang, S.-T., Kim, Y.-H., Min, J. 2011. Blue LED and succinic acid enhance the growth of Rhodobacter sphaeroides. World Journal of Microbiology and Biotechnology, 27(1), 189-192. Mascle-Allemand, C., Duquesne, K., Lebrun, R., Scheuring, S., Sturgis, J.N. 2010. Antenna mixing in photosynthetic membranes from Phaeospirillum molischianum. Proceedings of the National Academy of Sciences, 107(12), 5357-5362. Massé, A., Pringault, O., De, W.R. 2002. Experimental study of interactions between purple and green sulfur bacteria in sandy sediments exposed to illumination deprived of near-infrared wavelengths. Applied and Environmental Microbiology, 68(6), 2972-2981. Prachanurak, P., Chiemchaisri, C., Chiemchaisri, W., Yamamotob, K. 2014. Biomass production from fermented starch wastewater in photo-bioreactor with internal overflow recirculation. Bioresource Technology, 165(8), 129-136. Qin, Z., Zhang, P., Zhang, G. 2014a. Biomass and carotenoid production in photosynthetic bacteria wastewater treatment: Effects of light intensity. Bioresource Technology, 171, 330-335. Qin, Z., Zhang, P., Zhang, G. 2015. Biomass and pigments production in photosynthetic bacteria wastewater treatment: Effects of light photoperiod. Bioresource Technology, 190, 196-200. Qin, Z., Zhang, P., Zhang, G. 2014b. Biomass and pigments production in photosynthetic bacteria wastewater treatment: Effects of light sources. Bioresource Technology, 179, 505-509. Saikin, S.K., Khin, Y., Huh, J., Hannout, M., Wang, Y., Zare, F., Aspuruguzik, A., Tang, K.H. 2014. Chromatic acclimation and population dynamics of green sulfur bacteria 10 / 20
grown with spectrally tailored light. Scientific Reports, 4(3), 5057. Sasaki, K., Watanabe, M., Suda, Y., Ishizuka, A., Noparatnaraporn, N. 2005. Applications of photosynthetic bacteria for medical fields. Journal of Bioscience & Bioengineering, 100(5), 481-488. Stomp, M., Huisman, J., Stal, L.J., Matthijs, H.C.P. 2007. Colorful niches of phototrophic microorganisms shaped by vibrations of the water molecule. ISME J, 1(4), 271-282. Tamiaki, H., Matsunaga, S., Taira, Y., Wada, A., Kinoshita, Y., Kunieda, M. 2014. Synthesis of zinc 20-substituted bacteriochlorophyll-d analogs and their self-aggregation. Tetrahedron Letters, 55(22), 3351-3354. Yan, C., Luo, X., Zheng, Z. 2013. Effects of various LED light qualities and light intensity supply strategies on purification of slurry from anaerobic digestion process by Chlorella vulgaris. International Biodeterioration & Biodegradation, 79, 81-87.
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Fig. 1. Schematic diagram of experimental design.
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Fig. 2. Perturbation plot analysis of the effects of light intensity, light photoperiod and quality on NH4+-N removal (a) and COD removal (b). Design Expert 8.0® was used to form the perturbation. (A) light photoperiod; (B) light intensity; (C) light quality.
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Fig. 3. Response surface analysis of the interactive effects of key parameters on NH4+-N and COD removal. The response of NH4+-N and COD removal to different light intensity and light photoperiod at a constant light quality of 850 nm (a, d). The response of NH4+-N and COD removal to different light quality and light photoperiod at a constant light intensity of 4.25 W/m2 (b, e). The response of NH4+-N and COD removal to different light quality and light intensity at a constant light photoperiod of 20 min/10 min (c, f).
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Fig. 4. Effects of light quality (MNIR LED) on NH4+-N and COD removal (a, b), biomass and bacteriochlorophyll a production (c, d) in APB wastewater treatment.
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Fig. 5. Effects of MNIR LED on whole cells absorbance.
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Table 1 Box–Behnken experimental design with three independent variables and two responses. Run No.
Factor 1 C: light photoperiod a) (min)
Factor 2 B: light intensity b) (W/m 2)
Factor 3 A: light quality (nm)
Response 1 NH3-N removal (%)
Response 2 COD removal (%)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
25/5 15/15 20/10 20/10 25/5 20/10 15/15 20/10 25/5 15/15 20/10 20/10 20/10 20/10 25/5 15/15 20/10
4.25 4.25 4.25 8 0.5 4.25 8 4.25 8 0.5 0.5 0.5 4.25 4.25 4.25 4.25 8
760 760 850 940 850 850 850 850 850 850 760 940 850 850 940 940 760
52.51 38.59 52.51 35.25 43.16 57.78 41.97 60.42 46.35 38.11 40.75 29.43 46.02 68.33 32.34 37.56 42.84
64.55 46.85 65.84 45.89 53.62 67.13 53.6 69.06 63.91 50.38 51.02 37.54 61.33 77.28 41.52 46.51 60.04
Note: a) The photoperiod was designed to the light/dark (L/D) cycle, and 48 times every day (Qin et al., 2015). b) The light intensity was studied base on the surface area of the serum bottles.
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Table 2 ANOVA analysis response surface quadratic model. Removal
Source
F-Value
P-Value
Result
NH4+-N
Model Lack of Fit Model Lack of Fit
4.01 3.860E-003 9.78 0.041
0.0403 0.9996 0.0033 0.9873
significant not significant significant not significant
COD
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Table 3 Effects of light sources on APB growth as reported in the literature. PSB strains
Culture medium
Light sources
Optimum
References
Rhodopseudomona s
Sugar wastewate r
Red, yellow, blue, white LED and incandescent lamp
Red LED a)
(Qin et al., 2014b)
Cba. tepidum
Unknown
700 nm, 750 nm, 780 nm, 800 nm, 850 nm, 940 nm LED
800 nm LED
(Saikin et al., 2014)
b)
R. palustris
NS medium
Incandescent lamp, halogen lamp, fluorescence lamp, and white, yellow, red, blue and green LED
Blue LED a)
(Kuo et al., 2012)
R. sphaeroids
Sistrom’s minimal medium
Blue, green, red, white LED, fluorescent lamp
Blue LED b)
(Lee et al., 2011)
Rhodopseudomona s
Improved medium
850 nm LED
This study
760 nm, 850 nm, 940 nm NIR LED, Incandescent lamp Note: a) Biomass production; b) Growth rate.
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a)
Highlights
· Different MNIR LEDs were used for APB wastewater treatment. · The highest nutrient removal was predicted by RSM. · Light quality was the biggest impact factor in APB wastewater treatment. · MNIR LED could not only save energy, but also avoid algae bloom of PBR.
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