Comparison between Airlift Photobioreactor and Bubble Column for Skeletonema Costatum Cultivation

The cultivation of diatom Skeletonema costatum was achieved in airlift photobioreactor and the system performance was compared to that of bubble column. The standard F/2 medium (Guillard’s medium) for typical diatom cultivation could only yield the best growth character when the silicon concentration increased 4 times the normal value. In terms of cell growth, the airlift photobioreactor provided better performance than the bubble column where the maximum cell concentration, specific growth rate, and productivity in the airlift were 4.6 x 106 cell mL-1, 0.07 h-1, and 6.4 x 104 cell s-1 compared with 1.8 x 106 cell mL-1, 0.04 h-1, and 2.2 x 104 cell s-1 in the bubble column of the same size (3L) and operated at the same aeration rate (superficial velocity = 1.5 cm s-1) and light intensity (34 μmol photons m−2 s−1). This was because the airlift photobioreactor allowed circulatory flow in the system which helps prevent cell precipitation and enhance light utilization efficiency. The optimal operating conditions in the airlift system which was found most optimal to cell growth were: the ratio between downcomer and riser cross sectional area (Ad:Ar) of 3.27, superficial gas velocity 1.5 cm s−1 and the light intensity 34 μmol photons m−2 s−1. Preliminary economical assessment on the cultivation of S. costatum in airlift system compared with that in bubble column was carried out, whereas the analysis for nutritional values of the obtained biomass indicated relatively high protein content

Manipulation of Biochemical Compositions of Chlorella sp.

This work aimed to study the effect of several environmental parameters (light intensity, temperature, and aeration rate) on the accumulation of nutritional components and lutein production in a green microalgae Chlorella sp. It was proven in this work that the biochemical composition of Chlorella sp. could be manipulated through the control of environmental conditions during the cultivation. A simple 2L bubble column photobioreactors installed in a well controlled culture chamber was employed as a model system where temperature, light intensity, and aeration rate (usg) could be controlled in the range from 30 - 40ºC, 10 - 30 kLux, and 0.5 - 1.5 cm/s, respectively. Lipid and protein productivity were the most abundant at 35°C, 10 kLux and 1 cm/s, whereas carbohydrate productivity was found to be maximized at 30°C, 30 kLux and 0.5 cm/s. In addition, Chlorella sp. could also generate strong antioxidizing agents like lutein which was found to be mostly produced at 35°C, 10 kLux and 1 cm/s

Microalgal Lipid Extraction and Evaluation of Single-Step Biodiesel Production

This work examined solvent extraction of lipid from microalgae for production of renewable biofuels, thereby allowing appropriate selection of solvent and extraction methods. The results of this study revealed that the mixture of chloroform and methanol (C/M) at the ratio of 2:1 (v/v) could extract the highest amount of total lipid from algae, while hexane was found to be a good solvent, concerning the selectivity for nonpolar targeted lipids such as mono-, di- and tri-glycerides. As far as the extraction methods are concerned, applying ultrasound could accelerate the rate of lipid extraction from algae with tough cell walls such as Chlorella vulgaris. On the other hand, ultrasound and microwave assisted extraction techniques added no benefits to the extraction of lipid from powder of Haematococcus pluvialis whose cell wall was previously damaged. Other than lipid extraction, this paper concerns with the development of transesterification process for algal lipid using C. vulgaris as a model system. Here, the effects of the amount of catalyst, alcohol to biomass ratio and reaction time on biodiesel yield were investigated. We also studied a single-step biodiesel production where extraction and transesterification simultaneously take place, and made comparison between this method and the conventional two-step biodiesel production process

Synthesis and Testing of Zeolite from Industrial-Waste Coal Fly Ash as Sorbent For Water Adsorption from Ethanol Solution

In the present work, zeolite was prepared from industrial-waste coal fired ash (CFA) by fusion technique with and without acid-washing pretreatment under various conditions. The synthesized materials were then tested for water adsorption from bioethanol solution with an aim to produce a high purity ethanol (> 99.5%) for later utilization in gasohol production manufacturing. From our studies, it was found that the impurities (i.e., Fe2O3, TiO2, MgO, CaO, K2O and SO3) in CFA could be efficiently removed by acid-washing pretreatment. Among three different acids studied (i.e. HCl, HNO3, and H2SO4), HCl exhibited the highest pretreatment performance, while the most suitable pretreatment conditions to enhance high purity raw material (up to 85% purity) were by using 20% HCl with the acid to CFA ratio of 25 mlHCl/gCFA at 80°C for 3 h. After fusion at 550ºC with NaOH/CFA mass ratio of 2.25 and further crystallization at 90ºC for 4 h, the pretreated CFA was converted to zeolite; from which the main phases were sodium aluminum silicate hydrate (1.08Na2O•Al2O3•1.68SiO2•1.8H2O) and faujasite-Na (Na2Al2Si2.4O8.8•6.7H2O). Regarding water adsorption testing, the synthesized zeolite provided comparable adsorption performance with the commercial grade molecular sieve. Under three adsorption cycles testing at 85ºC, high ethanol purity (99.8%) could be achieved without deactivation being observed

Fractionation and Mobility of Lead in Klity Creek Riverbank Sediments, Kanchanaburi, Thailand

The sequential extraction method was employed to investigate the distribution and chemical fractions of lead (Pb) in Klity Creek sediments, Kanchanaburi, Thailand with the main objective to define the lead mobility in sediment and potential bioavailability in relation to sediment contamination levels. Samples were collected from a total of twelve sampling sites distributed from upstream of the polluted zone until the final downstream point at Srinakarin Reservoir. The results showed that the background value of total lead concentration in the sediments from this area was higher than those reported from other locations in Thailand. Sequential extraction results revealed that lead was mainly associated with the reducible fraction especially in the polluted zone in the vicinity of the ore dressing plant. This is different from the distribution of lead fractions upstream and downstream of the polluted area, i.e. reducible fraction was the major component upstream whereas strongly dissociated fractions (oxidizable and residual) were the major components for the downstream samples (at Srinakarin Reservoir). A significant amount of the lead fraction in the study area was rather mobile, suggesting it as readily available to living organisms. Most samples exhibited a medium risk level with Risk Assessment Code (RAC) values of more than 10%

Synthesis of Zeolite from Coal Fly Ash: Its Application as Water Sorbent

Coal fly ash (CFA) was used as raw material for zeolite synthesis by fusion method. In detail, it was mixed with NaOH (with ratio of 2.25) and treated under various temperatures. Synthesized zeolite was characterized using various techniques i.e. X-rayfluorescence (XRF), X-ray diffraction (XRD), and BET surface area analysis. It was found that the surface area of synthesized zeolite were in the range of 49.407-69.136 m2/g depending on the preparing condition, compared to the surface area of CFA about 17.163 m2/g. In addition, according to the XRD result, it was proven that the form of zeolite was Sodium Aluminum Silicate Hydrate (1.08Na2O.Al2O3.1.68SiO2.1.8H2O). The synthesized zeolite was then applied as water sorbent to remove water from ethanol solution (95%). The testing results revealed that the optimal fusion temperature was 450.C, which provided maximum percentage of water removal from ethanol solution (from 95% ethanol to 99.25% ethanol). For comparison, commercial-grade molecular sieve was also tested and was found to increase ethanol concentration from 95% to 99.61%. Hence, it is concluded that our synthesized zeolite provides comparable performance to the commercial-grade molecular sieve

Comparison between Airlift Photobioreactor and Bubble Column for Skeletonema Costatum Cultivation

The cultivation of diatom Skeletonema costatum was achieved in airlift photobioreactor and the system performance was compared to that of bubble column. The standard F/2 medium (Guillard’s medium) for typical diatom cultivation could only yield the best growth character when the silicon concentration increased 4 times the normal value. In terms of cell growth, the airlift photobioreactor provided better performance than the bubble column where the maximum cell concentration, specific growth rate, and productivity in the airlift were 4.6 x 106 cell mL-1, 0.07 h-1, and 6.4 x 104 cell s-1 compared with 1.8 x 106 cell mL-1, 0.04 h-1, and 2.2 x 104 cell s-1 in the bubble column of the same size (3L) and operated at the same aeration rate (superficial velocity = 1.5 cm s-1) and light intensity (34 μmol photons m−2 s−1). This was because the airlift photobioreactor allowed circulatory flow in the system which helps prevent cell precipitation and enhance light utilization efficiency. The optimal operating conditions in the airlift system which was found most optimal to cell growth were: the ratio between downcomer and riser cross sectional area (Ad:Ar) of 3.27, superficial gas velocity 1.5 cm s−1 and the light intensity 34 μmol photons m−2 s−1. Preliminary economical assessment on the cultivation of S. costatum in airlift system compared with that in bubble column was carried out, whereas the analysis for nutritional values of the obtained biomass indicated relatively high protein content

Evaluating environmental performance of concentrated latex production in Thailand

Thailand is currently the world's largest natural rubber producer. To maintain a leadership position of natural rubber producer, it has been challenging for Thai rubber entrepreneurs to seek appropriate measures towards producing environmentally friendly rubber products. The objective of this study is to assess the potential environmental impact of concentrated latex production by partial Life Cycle Assessment (LCA), and to investigate the effects of the options to reduce the impact. The methodology is based on the ISO 14040 series, taking a "Gate-to-Gate" approach (Partial LCA). The activities taken into account include production of chemicals, production of diesel and electricity, diesel combustion, and wastewater treatment. The functional unit is 1 ton of concentrated latex, and the environmental impacts considered in this study include global warming, acidification, eutrophication, human toxicity, photochemical oxidation, and the total environmental impact. The results indicate that electricity use for centrifugation has the largest share, compared with other activities, in global warming (50%), acidification (58%), and photochemical oxidation (55%). Ammonia use for latex preservation accounts for 37% of human toxicity, whereas use of DAP (Diammonium phosphate) accounts for 46% of eutrophication. Based on these results, the following reduction options are therefore identified: 1) electricity efficiency improvement (by installation of inverters to centrifugal machines); 2) improvement of ammonia preparation and storage (by chilling systems); 3) minimizing the use of DAP (by extending coagulation time); and 4) substitution of diesel by LPG. These four options were technically and practically feasible for concentrated latex production, and result in reductions of the total environmental impact by 12%, 8%, 3%, and 5%, respectively

Spatial Distribution and Mobility Factor of Heavy Metals in Agricultural Soil in the Vicinity of Abandoned Lead Ore Dressing Plant, Klity Village, Thailand

The concentration and mobility spatial distribution of heavy metals (lead, zinc, cadmium and chromium) including potential ecological risk have been evaluated for the polluted surface soil from mining activities in Upper Klity village, Thailand. Soil samples were collected from the residential and agricultural areas and the area of ore dressing plant. Heavy metals content presented higher in the ore dressing plant area than those found in residential and agricultural areas. Lead was the predominant polluted metal with two hot spots surrounding the ore dressing plant and open pit mine. Mobility distribution of these metals was followed closely with their concentration. Vertical soil profiles proved that mobility factors were only high at the top soil layer and became lower at deeper soil layers for all metals, and the quantities of lead, zinc, cadmium and chromium in both soil profiles can be ordered from large to small as: Reducible, Residual, Oxidizable, Acid extraction and Exchangeable fractions. These results indicated that the contamination was caused by anthropogenic mining activities. Potential Ecological Risk (PER) exhibited a low potential ecological risk with the averages of 3.79 and 81.3 in agricultural and ore dressing plant areas, respectively. However, most individual potential ecological risk values were small and classified as low for all heavy metals. This study recommends that heavy metals were unlikely to cause additional adverse health risk effects in residential and agricultural area. On the other hand, the risk of heavy metals pollution in the ore dressing plant area should be of primary concern

Biosorption of binary mixtures of heavy metals by green macro alga, Caulerpa lentillifera

Dried Caulerpa lentillifera was shown to have adsorption potential for Cu, Cd, Pb and Zn. The adsorption equilibrium was found to follow the Freundlich isotherm type. The adsorption of binary mixture of heavy metals solution onto the surface of the algae was found to be of competitive type where the adsorption capacity for any single metal decreased by 10-40% in the presence of the others. The total adsorption capacity of the algae was, in most cases, found to decrease by 30-50% when there was more than one heavy metal in the solution. However, the adsorption of mixtures of Cd and Cu, and of Pb and Cu did not show a reductionin the total adsorption capacity