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Abstrak :
Thammasat International Journal of Science and Technology (TIJSAT) contains original research articles, review articles, and short communications. The objectives are to publicize and promote the research contributions and innovative works in the fields associated with science and technology. Areas covered include: 1. Biological sciences such as biology, zoology, botany, genetics, agriculture, ecology. 2. Engineering such as electrical engineering, chemical engineering, civil engineering, environmental engineering, computer engineering; and information technology. 3. Health sciences such as medicine, dentistry, veterinary, pharmacy, physical therapy, nursing, public health. 4. Physical sciences such as chemistry, physics, mathematics, statistics. The journal is published 4 issues per year No.1 January-March, No.2 April-June, No.3 July-September and No.4 October-December. Thammasat International Journal of Science and Technology is currently indexed in both national and international electronic/online databases, namely, Thai-Journal Citation Index (TCI) Tier 1, Thai Journals Online (ThaiJO), ASEAN Citation Index (ACI), Elektronische Zeitschriftenbibliothek (EZB).

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Reduction of free fatty acid (FFA) in used palm oil was determined after treatment of waste cooking oil with an adsorbent derived from coffee bean husk ash. Coffee husks were burned at 600 ºC for 12 hrs to obtain the adsorbent ash. Free fatty acid removal efficiency was optimized with respect to ash dosage, contact time and temperature. It was found that shaking ash (1 g) with waste palm oil (50 g) at 250 rpm and 30°C for 330 min gave the highest reduction in free fatty acids (FFA) (1966 mg/g). The adsorption isotherm was followed by Temkin (R2 = 0.9283) and Freundlich models (R2 = 0.9146). The adsorption of FFA at all adsorbent doses followed pseudo-second order kinetics (R2 = 0.9817-0.9999). A thermodynamic study revealed that the changes in enthalpy, entropy and Gibbs free energy were 89.07 kJ/mol, -0.25 kJ/mol.K and -5.15 to -12.17 kJ/mol, respectively. The coffee husk ash (5 g ash / 50 g waste palm oil) was found to reduce FFA by 100% at 30°C. Keywords Coffee husk, Used palm oil, Free fatty acid, Adsorption, Ash

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Ammonia and phosphorus have been recognized as the cause of eutrophication in surface water. Chuat Man Canal is faced with water quality degradation problem due to the high concentrations of ammonia and total phosphorus in the water body that makes it unsuitable for fish ponds. Removal of ammonia and phosphorus by the adsorption process is simple and not requires chemical use. In addition, ammonia is well adsorbed by activated carbon and zeolite while phosphorus is adsorbed by zeolite. This research used zeolite and activated carbon for the adsorption of ammonia and total phosphorus. The results of laboratory experiments at 30 °C 200 rpm 60 minutes, revealed that adsorption of ammonia using zeolite correlated with Freundlich isotherm (R2 = 0.9031). For ammonia adsorption using activated carbon, it correlated with Langmuir (R2 = 0.9596) and Freundlich (R2 = 0.9113) isotherms, respectively. For field experiment, 9 zeolite and activated carbon adsorbent pads with ratio of 1.6:1 by weight were placed across the canal sections. Each pad had 2 openings and each opening contained its adsorbent volume of 1.0 × 0.015 × 0.6 m3 (width × length × height). The front opening contained 5 kg of activated carbon while the back part contained 8 kg of zeolite. During the study, water flow velocity at surface of water was ranged from 0.022 - 0.027 m/s. Concentration of ammonia in influent and effluent was ranged from 1.755- 8.817 mg/L and 1.473-7.063 mg/L, respectively while that for total phosphorus was ranged from 0.045 - 0.095 mg/L and 0.042 - 0.089 mg/L, respectively. The maximum removal efficiency occurred 20 and 43 minutes after installation of the adsorption pads which were 6.73% for total phosphorus and 23.17% for ammonia, respectively.

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The objective of the present study is to investigate the influence of external magnetic field on unsteady incompressible flow of water based nanofluid through a successively expanding or contracting channel with porous walls. the basic governing equations with boundary conditions are non-dimensionalized using appropriate transformation to ordinary differential equations, which are then solved using power series with the help of Hermite-Padè approximation method. the instability of the flow is shown using bifurcation graph and the dominating singularity behavior numerically. the regular effects of the different governing physical parameters specifically Hartmann number, volume friction of nanoparticles, non-dimensional shear stress and permeation Reynolds number on velocity profiles are depicted graphically.

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The objective of this study was to determine the activity of erector spinae muscle in four techniques of lifting phase of manual human handling; two-handed seat carry, four-handed seat carry, fore-and-aft carry and chair carry. Thirty-two (16 couples) healthy young men lifted subjects weighing 60±5 kg from table heights of 50 cm and 100 cm. Surface electromyography was used to evaluate lumbar erector spinae activity during lifting. The four-handed seat carry technique had the highest average of lumbar erector spinae activity both from table height 50 cm and 100 cm. This may be due to more trunk flexion movement than in other techniques. The lowest activity of lumbar erector spinae was found in fore-and-aft carry and chair carry techniques. Moreover, lifting from table height 50 cm had more lumbar erector spinae muscle activity than lifting from table height 100 cm in 3 techniques (two-handed seat carry, four-handed seat carry and fore-and-aft carry). The highest activity of lumbar erector spinae muscle in the four-handed seat carry technique indicated risk of low back pain during lifting, especially lifting people from a table height of 50 cm. Lower lumbar erector spinae muscle activity in fore-and-aft carry and chair carry techniques indicated safer they are safer techniques for lifting.

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To overcome the disadvantages of open pond and cement tube as an outdoor algal cultured system, a simple inclined algal culture system was developed. the system composed of an 18.9 L polyethylene terephthalate (PET)bottle placed on a degree adjustable stand using an air pump to generate water mixing and circulation. The system was tested by culturing 45 mL Oscillatoria sp. in 13 L Blue-Green-11 (BG-11)medium supplemented with 3 g L-1 NaNO3 in plastic bottle, which was placed on different angles of inclination, viz. 45°, 60° and 90°. The system was operated outdoor under natural daylight and temperature. After 11 days, 11.5 L culture medium was poured out and 11.5 L fresh medium was refilled. Algal cell was precipitated to measure algal yield. Then, cell harvesting was done every 7 days for 6 batches. This system could culture algae continuously for 5 batches. The highest productivity was 32.23 gram wet (gw) ×m-2×d-1, which was recorded from a second and fifth round of 45° angular system and also from third round of 60° angular system. The result showed that this simple inclined algal culture system can be done continuously for one and a half month with high productivity by 45° inclination, which was proved as a good mixing and circulation. Showing advantages over open-pond, this system was moveable and could reduce possibility of contamination.

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This study aims to investigate the feasibility of using a minimal glycerol medium with inorganic salt supplementation for a low-cost dihydroxyacetone (DHA) production by bacteria. Acetic acid bacterial isolates of Gluconobacter and Asaia, which are found in the Northern, North-Eastern, Middle, Western, and Southern regions of Thailand, were evaluated for their ability to produce DHA using glycerol as a carbon source. During the qualitative screening, 66 isolates, including Gluconobacter (61 isolates) and Asaia (5 isolates), from a total of 486 isolates showed highly positive results by the Fehling test. The 5 isolates of Asaia gave low DHA production in the quantitative screening, whereas Gluconobacter isolates showed DHA production at low (0-5.70 g/L), medium (5.71-11.40 g/L), and high (11.41-16.89 g/L) levels. Preliminary culture medium optimizations for G. frateurii BCC 36199, a most promising microorganism for DHA production, were also carried out using a low-cost minimal glycerol medium supplemented with an inorganic salt. G. frateurii BCC 36199 produced 18.67 g/L of DHA with ysp of 95.44% (DHA moles/glycerol moles) at 30°C, 20 g/L of glycerol, and pH 4.5. The cultivation of G. frateurii BCC 36199 in the developed minimal glycerol medium is practical and can be further optimized in order to apply for industry.

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The study was concerned with the effects of the organic loading as food/microbe (F/M) and nitrogen concentration as BOD5: TN on the sequencing batch reactor (SBR) system efficiency and performance with 1:5 diluted-electroplating wastewater (EPWW) solutions. The results showed that chemical oxygen demand (COD) and biological oxygen demand (BOD5) removal efficiencies were almost the same with the organic loadings of 0.125-0.375 kg BOD5/m3.d. The CN- and Zn2+ loadings of 1.2-2.9 and 1.6-4.0 g/m3.d did not show strong repression effects to the COD and BOD5 removal efficiencies. In addition, the high Zn2+ removal efficiency level of 94-96% was detected. Moreover, the system did not show any difference in Zn2+ and COD removal efficiencies at the BOD5: TN ratios of 100:5-100:10. Urea and (NH4)2SO4 could be used as the nitrogen source of 1:5 diluted-electroplating wastewater solution. The highest COD, BOD5, Zn2+, CN-, Total Kjeldahl nitrogen (TKN) and total nitrogen (TN) removal efficiencies of 98.0±0.2, 97.0±0.7, 97.7±0.1, 93.3±1.2, 86.5±1.1 and 80.9±0.5%, respectively, were detected at the BOD5:TN ratio of 100:10 and (NH4)2SO4 was used as the nitrogen source. The system also showed good bio-sludge performance with the Sludge Volume Index (SVI) and Sludge Retention Time (SRT) values of 51±4 mL/g and 29±3 days, respectively.