Đang tải... (xem toàn văn)
VIETNAM JOURNAL OF CHEMISTRY VOL 51(3) 384 389 JUNE 2013 CULTURING CHLORELLA VULGARIS IN ANAEROBICALLY DIGESTED PIGGERY WASTEWATER FOR CONCOMITANT NUTRIENT REMOVAL AND BIODIESEL FEEDSTOCK PRODUCTION D[.]
VIETNAM JOURNAL OF CHEMISTRY VOL 51(3) 384-389 JUNE 2013 CULTURING CHLORELLA VULGARIS IN ANAEROBICALLY DIGESTED PIGGERY WASTEWATER FOR CONCOMITANT NUTRIENT REMOVAL AND BIODIESEL FEEDSTOCK PRODUCTION Doan Thi Thai Yen*, Nguyen Minh Giang Institute for Environmental Science and Technology, Hanoi University of Science and Technology Received 14 September 2012 Abstract Anaerobic digestion of piggery manure generates effluents which containing high concentration of inorganic nitrogen and phosphorus and causes eutrophication when discharged into natural water bodies Microalgae can be cultured in an anaerobic eflluent as a required tertiary treatment as well as for biodiesel feedstock production In this study, anaerobic digested piggery effluent was used as nutrients source for culturing green microalgae Chlorella vulgaris The effect of dilution of the anaerobically digested piggery effluent nutrients removal efficiency of Chlorella vulgaris was determined During days in batch culture, Chlorella vulgaris grew faster m the more diluted wastewater, which related to initial COD concentration of about 400 mg/L, The maximum specific growth rate and biomass concentration were 0.306 day"' and 0.191 g/L, respectively, Microalgae removed ammonia, total phosphorus and COD by 60-95.8%, 22-68% and 34-73.8%, respectively The lipid contents of algal biomass after day were 28-30% of dry weight, which could be utilized as a feedstock for biodiesel production Keywords' Piggery wastewater, Chlorella vulgaris, biodiesel feedstock, nutrient removal, lipid content 1, INTRODUCTION The potential of microalgae as a base biofuel resource has been recognised with exploratory research projects developed in the 1980's and early 1990's [1] Currently, the rationale for extensive development of renewable fuel resources is seen as key to management of world energy demands in a sustainable manner [2], and microalgae have the capability to produce bigh-lipid content biomass, as precursor for liquid biofuels that does not conflict with food production [3] To date, great efforts have been concenfrating on reducing the costs of producing biodiesel from microalgae One of them is reuse of digested piggery wastewater for microalgae cultivation for biofuel feedstock [4, 5], Digested piggery effluent could be an alternative nutrient source for mass microalgal production since anaerobically treated waste contains nutinents such as N and P (NH,*, NO3", PO,,^") which are suitable for growing algae Additional, pathogens in the digested effluent were eliminated particular after two-stage (thermophilic and mesopbilic) digestion Therefore, digested effluent as medium of algal culhire could alternative costly mineral medium, which cause to less utilize fresh water and remove effectively piggery wastewater The sfrain of Chlorella vulgaris used in the present study is popular for wastewater freatment and biodiesel feedstock [6, 7] C vulgaris was found to mixofropbically grow in diluted piggery wastewater from a local pig farm The relationships between the initial COD values and properties such as the growth rate, the elimination of nutiients (NH4'-N, TKN, P04'"-P, total P and COD) and the algal lipid content were individually investigated MATERL\LS AND METHODS 2.1 Microalgal strain and culture conditions Chlorella vulgaris was locally isolated from a pond in Co Dong pig farm Son Tay, Hanoi The sti^in was cultured in Bold' Basal Medium with vitamins (BBM+V) as described in [8] Culture flasks were maintained at room temperature (2532°C) under static condition Light irradiation was 1500 lux using cool-white fluorescence tubes, with a 12:12 h of light:dark cycle Light intensity was measured at the surface of the culture broth using a Testo 545 lux meter (Testo GmbH & Co, Germany) VJCVoL 51(3), 2013 Doan Thi Thai Yen, et al 2.2 Sampling site of piggery wastewater 2.5 Biomass dry weight (DW) The samples of piggery wastewater were collected at an effluent from an upflow anaerobic sludge blanket (UASB) freatment system in a pig farm at Sontay, Hanoi, as displayed in Fig The samples were ti-ansported to laboratory, and then filtered over a glass cotton layer to removal suspended solids Before culturing microalgae, the samples were diluted witb distilled water to get several levels of COD concenfrations Biomass dry weight was determined as follows: On the terminated day of experiments, 50 mL of microalgae suspension was sampled and filtered on a pre-weigbed Whatman GF/F glass fiber filter (0.7 pm pore size and 47 mm diameter; Whatman, USA) using a Kontec Ulfra-ware microfilfration apparatus The algal pellets were dried overnight at 80°C and weighed, 2.6 Total lipid content -^-xir*'fffti^f&Fig I: Sampling site in the pig farm at Son Tay, Hanoi 2.3 Diluted wastewater to various COD concentrations Digested wastewater was diluted to different concentrations of COD, i.e 250, 300, 400, 530, 600 and 740 mg/L, C vulgaris was inoculated in 250 mL conical flasks containing 100 mL of various diluted piggery wastewater (triplicate cultures for each COD concenfration) The expenment flasks were manually shaken three limes a day to ensure microalgal cells in suspension All expenmenls were terminated at day 8' Total lipid content of microalgae was exfracted from the dry biomass using a modified solvent based on die method descnbed by Folch et al [9] and then quantified gravimefrically The dry biomass was fransferred into a cenfrifuge tube containing a mixture of chloroform :methanol (2:1, v/v), vigorously shaked and placed into an ulfrasonic water bath (TELSONIC Ulfrasonic Inc., USA) for hours Then, the supernatant was collected by pipette and transferred into another cenfrifiige tube The extraction procedure was repeated twice to ensure adequate lipid extiaction NaCI 0.9% solution was added to supernatant to make the ratio of lipid solution: solvent to be 1:5, v/v The centnfuge tube was then vortex mixed for minutes and allowed to phase separation for 15 minutes Collecting the bottom layer of the centiifuge tiabe and deposited into a pre-weigbed aluminum fray The aluminum tray was placed into an fume hood to evaporate solvent, then was dned overnight at 80°C and reweighed, 2.7 Nutrients removal efficiency C vulgaris was cultivated in diluted wastewater for days and then efficiencies of nufrient removal, The growth rate of each sti^in was characterized i.e chemical oxygen demand (COD), total Kjeldahl based on measurement of cell density every days, nifrogen (TKN) and total phosphorus (Total P), were using a specfrophotometiy UV/VIS Lambda EZ210 examined The analysis of COD, NH/-N and total P (PerkinElmer, USA), at X = 680 nm The specific was conducted according to Standard Methods for growth rate of each microalgae sfrain was calculated the Examination of Water and Wastewater [10] The from the slope of linear regression of time (days) nutiient removal efficiency was calculated as follows: and cell density (cells/mL): 2.4 Determination of cell growth rate \nOD,-\nOD