Hee-Jeong Choi

A mini review: photobioreactors for large scale algal cultivation.

AbstractMicroalgae cultivation has gained much interest in terms of the production of foods, biofuels, and bioactive compounds and offers a great potential option for cleaning the environment through CO2 sequestration and wastewater treatment. Although open pond cultivation is most affordable option, there tends to be insufficient control on growth conditions and the risk of contamination. In contrast, while providing minimal risk of contamination, closed photobioreactors offer better control on culture conditions, such as: CO2 supply, water supply, optimal temperatures, efficient exposure to light, culture density, pH levels, and mixing rates. For a large scale production of biomass, efficient photobioreactors are required. This review paper describes general design considerations pertaining to photobioreactor systems, in order to cultivate microalgae for biomass production. It also discusses the current challenges in designing of photobioreactors for the production of low-cost biomass.

A novel optical panel photobioreactor for cultivation of microalgae.

In this study, a novel optical panel photobioreactor (OPPBR) equipped with a V-cut/or flat optical panel (OP) and a light source, i.e., light-emitting diodes (LEDs) was developed. The performance of this OPPBR was assessed using cultures of Chlorella vulgaris. Growth rates of biomass were compared in bioreactors operated separately using a V-cut OP, or a flat-plate OP both equipped with LEDs or a fluorescent light source without any OP. The experiments were conducted at neutral pH (7.2 ± 0.3) with an initial cell concentration of 0.15 ± 0.05 g L(-1), at 23 ± 1 °C under dark and light cycles of 8 and 16 h, respectively, using LEDs and fluorescent lamps for 11 days. The results demonstrated that the amount of biomass produced using the V-cut OP was three times higher than the flat-plate OP and five times higher than without the OP. Parametric studies demonstrated that a distance of 3 mm between the OP and the LEDs produced the highest illumination uniformity, i.e., 65.7% for the flat-plate OP and 87.6% for the V-cut OP. The OPPBR system can be scaled up and could be used to enhance biomass production using an LED and OP combination.

Influence of the wastewater composition on denitrification and biological p-removal in the S-DN-P-process (b) Effect of acetate

The effect of acetate was examined during the p-removal and denitrification of wastewater. The plant was operated based on the sequencing-batch-biofilm-reactor (SBBR) process. As microbial media, ca. 9 mm Bio-Flow granules made from polyethylene and polypropylene were used. Three preparations were made to compare the level of biological p-removal and denitrification. In comparison to the batch test, 42 mg/L (AC 30) and 84 mg/L (AC 60) of NaCH(3)COO were mixed with the 500 mL of raw wastewater and the effect of the acetate concentration on the level of p-removal was monitored. All samples were immediately filtered with 0.45 microm membrane filter, and PO(4)-P, NO(3)-N, NO(2)-N and acetate were analyzed using Ion Chromatography, whereas P(total) and chemical oxygen demand (COD) were measured by a spectrophotometer. The p-removals for the WW, WW+AC 30 and WW+AC 60 preparations were found to be 9.4, 9.1 and 13.1mg/L, respectively. The WW+AC 30 preparation did not show any significant effect on the p-removal, while p-removal in WW+AC 60 preparation was higher than that in the other two preparations. A comparison of the data revealed the COD: NO(3)-N:AC:P ratio of the WW, WW+AC 30 and WW+AC 60 preparations to be 18.07:2.90:6.87:1, 21.28:2.45:5.98:1 and 15.95:2.75:6.18:1, respectively. The experimental results showed that approximately 7 mg/L of acetate was consumed per 1mg/L of p-removal.

Comparison between a moving bed bioreactor and a fixed bed bioreactor for biological phosphate removal and denitrification.

Moving bed bioreactors (MBBR) and fixed bed bioreactors (FBBR) were compared for biological phosphorus removal and denitrification. The sorption denitrification P-elimination (S-DN-P) process was selected for this study. Results indicated that all nutrients were removed by the FBBR process compared with the MBBR process: 19.8% (total COD), 35.5% (filtered COD), 27.6% (BOD(5)), 62.2% (acetate), 78.5% (PO(4)-P), and 54.2% (NO(3)-N) in MBBR; 49.7% (total COD), 54.0% (filtered COD), 63.2% (BOD(5)), 99.6% (acetate), 98.6% (PO(4)-P), and 75.9% (NO(3)-N) in FBBR. The phosphate uptake and NO(3)-N decomposition in the FBBR process during the denitrification phase were much higher than for the MBBR process despite being of shorter duration. Results obtained from this study are helpful in elucidating the practical implications of using MBBR and FBBR for the removal of bio-P and denitrification from wastewater.

Effect of particle size distribution in wastewater on the performance of nutrient removal process

Abstract The present investigation aims to explore the effect of particle size distribution in wastewater on the performance of sorption denitrification phosphorus removal process (S-DN-P process). The wastewater was obtained from the Wassmansdorf sewage plant in Berlin, which was denoted as the wastewater (WW). Further, the filtrates of wastewater fractions, obtained by sequential filtration using different pore size filters i.e. 3, 0.45, and 0.1 μm, were denoted by WW(3), WW(0.45), and WW(0.1). The P-removal was obtained to be 16.6, 9.0, 6.2, and 8.0 mg/L, respectively, for the wastewater samples WW, WW(3), WW(0.45), and WW(0.1). P-removal was decreased with decreasing pore size, except for the fraction WW(0.1). It was further observed that the ratios, COD:NO3-N:Acetate:P, were found to be 8.04:1.93:3.55:1, 19.94:2.82:6.88:1, 16.29:3.26:10.23:1 and 13.50:2.54:7.41:1, respectively, for the fractions WW, WW(3), WW(0.45), and WW(0.1). Moreover, approximately 3.5 mg acetate/mg P removed for WW, 7 mg acetate...

Effect of Temperature, Light Intensity and pH on the Growth Rate of Chlorella Vulgaris

The aim of this study was to investigate the efficiency of temperature, light intensity and pH on the growth rate of Chlorella vulgaris (C. vulgaris). The size of C. vulgaris (FC-16) was 3-8 µm, having round in shape. The cells of C. vulgaris (FC-16) was cultured in the Jaworskis Medium with deionized water. To evaluate the efficiency of temperature, light intensity and pH on the growth rate of C. vulgaris, six different fractions of temperature (10℃, 15℃, 20℃, 25℃, 30℃, 35℃), various light intensities (100-800 µEm -2 s -1 ) and seven different fractions of pH (3, 4, 5, 6, 7, 7.5, 9) were prepared. The growth rate of C. vulgaris cultivation was approximately 5.2 to 5.5 times faster, the concentration of Chlorophyll a was also 5 to 5.5 times higher, and cell volume per unit area was 14% higher at 25℃ to 30℃ than those at 10℃. Therefore, the optimal temperature for cultivation of C. vulgaris was estimated 25℃ to 30℃. The growth rate of C. vulgaris increased slowly up to 5 days, exploded after 5 days until 15 days, and then stoped after that. The optimum cultivation period of C. vulgaris was estimated as 15 days. The optimum pH for the growth rate of C. vulgaris was determined pH 7 to 7.5.

Integration of microalgal cultivation system for wastewater remediation and sustainable biomass production

Untreated wastewaters have been a great concern and can cause major pollution problems for environment. Conventional approaches for treating wastewater involve tremendous capital cost, have major short comings and are not sustainable. Microalgae culture offers an interesting step for wastewater treatment. Microalgae serve the dual purpose of phycoremediation along with the production of potentially valuable biomass, which can be used for several purposes. The ability of microalgae to accumulate nitrogen, phosphorus, heavy metals and other toxic compounds can be integrated with wastewater treatment system to offer an elegant solution towards tertiary and quaternary treatment. The current review explores possible role of microalgal based wastewater treatment and explores the current progress, key challenges, limitations and future prospects with special emphasis on strategies involved in harvesting, boosting biomass and lipid yield.

Effect of Photo Bioreactor with Optical Panel on the Growth Rate of Chlorella vulgaris

The aim of this study was to investigate the efficiency of optical panel (OP) on the growth rate of Chlorella vulgaris (C. vulgaris). The size of C. vulgaris (FC-16) was 3~8 μm, having round in shape. The cells of C. vulgaris was cultured in the Jaworski’s Medium with deionized water at 22°C for 15 days. For this experiment, three light samples were prepared to evaluate the efficiency of OP on the growth rate of C. vulgaris; OP with LED (Light Emitting Diode) (Run 1), Fluorescent light (Run 2) and LED (Run 3). The specific growth rate of C. vulgaris for Run 1 was found to be 14 times and 5 times faster than Run 2 and Run 3, respectively. In addition, the average biomass of C. vulgaris for Run 1 was measured 11.79 g/L in 11 days. This means that the biomass for Run 1 was reached 30 times and 6.5 times higher than Run 2 and Run 3, respectively. This may be due to the fact the OP was increased the light uniformity and hindered the shading effects in photobioreactor. Therefore, the growth rate of biomass in photobioreactor with OP is compared better than the without OP used other photobioreactor.

Influence of the wastewater composition on denitrification and biological P-removal in the S-DN-P process: (c) dissolved and undissolved substrates.

The denitrification and P-removal in the sorption-denitrification-P-removal (S-DN-P) process were carried out under various wastewater compositions. It is noted that P-removal largely depends on the wastewater composition as well to the quantity of the substrates present in wastewater fraction. Three different wastewater fractions are obtained as: raw wastewater, dissolved wastewater (obtained with filtration using 0.45 microm filter), and undissolved wastewater (i.e., infiltrate obtained by above filtration). The ratio of P-release/COD(tolal)-consumption clearly inferred that undissolved wastewater possess very low value i.e., 0.0008 followed by raw wastewater 0.008 and dissolved wastewater 0.03. When this ratio was nearby 0.01, enhanced P-removal was observed. Moreover, the ratio of P-uptake to NO3(-)-N decomposition for raw wastewater was two times for dissolved wastewater. Interestingly, it was observed that the P-removal and denitrification depend not only on the dissolved substrates but also the undissolved substrates present in the wastewater. The result of the P-removal obtained with this S-DN-P process did not show a big difference of 36%, 34% and 30%, respectively, for raw, dissolved and undissolved wastewater.

Use of methyl esterified eggshell membrane for treatment of aqueous solutions contaminated with anionic sulfur dye

The present study assessed the adsorption of an anionic dye (sulfur blue) by methyl-esterified eggshell membrane (MESM), a low-cost and abundant material from waste. Adsorption kinetics were investigated using parameters such as pH, contact time, initial dye concentration, solution temperature, dosage of adsorbent, and particle size of adsorbent. After methyl esterification, the specific surface area significantly increased and the negative surface charge of the eggshell membrane changed to positive for all pH values, which increased the sulfur dye sorption capacity. The optimal conditions for sorption of sulfur dye onto MESM resulted in >98% removal and were as follows: <35 μm particle size, pH 8, 20 min contact time and 313 K temperature. In this respect, 0.68-0.73 dry weight mg/L sulfur dye was adsorbed per 1 mg/L MESM. The Langmuir adsorption capacity for sulfur dye was 187.6 mg/g. In addition, sulfur removal was spontaneous and uptake was endothermic. MESM is an inexpensive and effective adsorbent.