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Jung K.,Korea District Heating Corporation | Jang T.,Chonbuk National University | Jeong H.,Seoul National University | Park S.,Seoul National University
Agricultural Water Management | Year: 2014

The objective of this study is to assess the growth and yield components of rice irrigated with reclaimed domestic wastewater. The experimental plots consisted of four blocks of each of the three irrigation water treatments: groundwater, untreated wastewater, and reclaimed wastewater. Randomized complete block design was applied to the experimental plots (5. m. ×. 5. m). Soil and water quality were monitored during a five cropping period. Crop height and tiller number data were analyzed from 2005 to 2009 according to growth stage. Analysis of variance (ANOVA) and honestly significant difference (HSD) post-hoc tests were applied to compare the rice components and yields from the treatments with the control plot. The wastewater and reclaimed wastewater irrigation plots were significantly higher than groundwater in clum length, panicle number, and rice yield. The total nutrients supplied with irrigation water were highly correlated with rice yield data, suggesting that the higher rice yield from reclaimed wastewater resulted from nutrient supply. The heavy metal contents in the milled rice that was cultivated with the reclaimed wastewater did not show significant differences from rice irrigated with groundwater. Reclaimed wastewater irrigation plots were significantly higher than groundwater irrigation plots in the contents of protein and milled head rice ratio, which had levels similar to or in the middle of conventional rice and brand rice. This study shows that reclaimed wastewater irrigation did not have adverse environmental impacts on the agricultural ecosystem, although long-term monitoring is needed to fully understand its relationships. © 2014 Elsevier B.V. Source

Lee K.,Korea Institute of Energy Research | Lee S.Y.,Korea Institute of Energy Research | Lee S.Y.,Chungnam National University | Na J.-G.,Korea Institute of Energy Research | And 5 more authors.
Bioresource Technology | Year: 2013

The consumption of energy and resources such as water in the cultivation and harvesting steps should be minimized to reduce the overall cost of biodiesel production from microalgae. Here we present a biocompatible and rapid magnetophoretic harvesting process of oleaginous microalgae by using chitosan-Fe3O4 nanoparticle composites. Over 99% of microalgae was harvested by using the composites and the external magnetic field without changing the pH of culture medium so that it may be reused for microalgal culture without adverse effect on the cell growth. Depending on the working volume (20-500mL) and the strength of surface magnetic-field (3400-9200G), the process of harvesting microalgae took only 2-5min. The method presented here not only utilizes permanent magnets without additional energy for fast harvesting but also recycles the medium effectively for further cultivation of microalgae, looking ahead to a large scale economic microalgae-based biorefinement. © 2013 Elsevier Ltd. Source

Yoo J.J.,Korea University | Choi S.P.,Korea University | Kim J.Y.H.,Korea University | Chang W.S.,Korea District Heating Corporation | Sim S.J.,Korea University
Bioprocess and Biosystems Engineering | Year: 2013

Photosynthetic microalgae have received much attention as a microbial source of diverse useful biomaterials through CO2 fixation and various types of photo-bioreactors have been developed for efficient microalgal cultivation. Herein, we developed a novel thin-film photo-bioreactor, which was made of cast polypropylene film, considering outdoor mass cultivation. To develop optimal design of photo-bioreactor, we tested performance of three shapes of thin-film photo-bioreactors (flat, horizontal and vertical tubular shapes) and various parts in the bioreactor. Collectively, vertical tubular bioreactor with H/D ratio 6:1 and cylindrical stainless steel spargers showed the most outstanding performance. Furthermore, the photo-bioreactor was successfully applied to the cultivation of other microalgae such as Chlamydomonas reinhardtii and Chlorella vulgaris. The scalability of photo-bioreactor was confirmed by gradually increasing culture volume from 4 to 25 L and the biomass productivity of each reactor was quite consistent (0.05-0.07 g/L/day) during the cultivation of H. pluvialis under indoor and outdoor conditions. Especially, we also achieved dry cell weight of 4.64 g/L and astaxanthin yield of 218.16 mg/L through long-term cultivation (100 days) under outdoor condition in 15 L photo-bioreactor using Haematococcus pluvialis, which means that the astaxanthin yield from outdoor cultivation is equal or superior to that obtained from controlled indoor condition. Therefore, these results indicate that we can apply this approach to development of optimal photo-bioreactor for the large-scale culture of microalgae and production of useful biomaterials under outdoor condition. © 2013 Springer-Verlag Berlin Heidelberg. Source

Yoon S.Y.,Korea University | Hong M.E.,Sungkyunkwan University | Chang W.S.,Korea District Heating Corporation | Sim S.J.,Korea University
Bioprocess and Biosystems Engineering | Year: 2015

Under autotrophic conditions, highly productive biodiesel production was achieved using a semi-continuous culture system in Neochloris oleoabundans. In particular, the flue gas generated by combustion of liquefied natural gas and natural solar radiation was used for cost-effective microalgal culture system. In semi-continuous culture, the greater part (∼80 %) of the culture volume containing vegetative cells grown under nitrogen-replete conditions in a first photobioreactor (PBR) was directly transferred to a second PBR and cultured sequentially under nitrogen-depleted conditions for accelerating oil accumulation. As a result, in semi-continuous culture, the productivities of biomass and biodiesel in the cells were increased by 58 % (growth phase) and 51 % (induction phase) compared to the cells in batch culture, respectively. The semi-continuous culture system using two stage photobioreactors is a very efficient strategy to further improve biodiesel production from microalgae under photoautotrophic conditions. © Springer-Verlag 2015. Source

Lee J.C.,Seoul National University of Science and Technology | Kim J.H.,Seoul National University of Science and Technology | Chang W.S.,Korea District Heating Corporation | Pak D.,Seoul National University of Science and Technology
Journal of Chemical Technology and Biotechnology | Year: 2012

BACKGROUND: Biological conversion of CO 2 to useful carbonic compounds such as methane is a potentially attractive technology for reducing its concentration in the atmosphere. One of the advantages of this technology over chemical conversion is that it requires much lower energy for reduction of CO 2. In this article, biological conversion of CO 2 to CH 4 using hydrogenotrophic methanogens was examined in a fixed bed reactor inoculated with anaerobic mixed culture from the anaerobic digestor of a sewage treatment plant. RESULTS: Methane formation commenced on the first day of operation of the fixed bed reactor. CO 2 fed to the reactor was reduced with H 2 by hydrogenotrophic methanogens. The feed ratio of CO 2 to H 2 is an important factor in determining the conversion rate of CO 2. When the feed ratio is 4, methane is produced at the expected rate according to the chemical equation. The CO 2 conversion rate was 100% when the gas retention time was 3.8 h in the fixed bed reactor. CONCLUSIONS: The results show that the fixed bed reactor employing hydrogentrophic methanogens has the potential to be effective in converting CO 2 to CH 4 with a conversion rate of 100% at 3.8 h retention time. © 2012 Society of Chemical Industry. Source

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