Piyarat Boonsawang

Effect of nitrate on the performance of single chamber air cathode microbial fuel cells

The effect of nitrate on the performance of a single chamber air cathode MFC system and the denitrification activity in the system were investigated. The maximum voltage output was not affected by 8.0mM nitrate in the medium solution at higher external resistance (270-1000Omega), but affected at lower resistance (150Omega) possibly due to the low organic carbon availability. The Coulombic efficiency was greatly affected by the nitrate concentration possibly due to the competition between the electricity generation and denitrification processes. Over 84-90% of nitrate (0.8-8.0mM) was removed from the single chamber MFCs in less than 8h in the first batch. After 4-month operation, over 85% of nitrate (8.0mM) was removed in 1h after the MFC was continuously fed with a medium solution containing nitrate. Only a small amount of nitrite (<0.01mM) was detected during the denitrification process. The similar denitrification activity observed at different external resistances (1000 and 270Omega) and open circuit mode indicates that the denitrification was not significantly affected by the electricity generation process. No electricity was generated when the MFC fed with 8.0mM nitrate was moved to a glove box (no oxygen), indicating that the bacteria on the cathode did not involve in accepting electrons from the circuit to reduce the nitrate. Denaturing Gradient Gel Electrophoresis (DGGE) profiles demonstrate a similar bacterial community composition on the electrodes and in the solution but with different dominant species.

Removal of H2S in down-flow GAC biofiltration using sulfide oxidizing bacteria from concentrated latex wastewater

A biofiltration system with sulfur oxidizing bacteria immobilized on granular activated carbon (GAC) as packing materials had a good potential when used to eliminate H(2)S. The sulfur oxidizing bacteria were stimulated from concentrated latex wastewater with sulfur supplement under aerobic condition. Afterward, it was immobilized on GAC to test the performance of cell-immobilized GAC biofilter. In this study, the effect of inlet H(2)S concentration, H(2)S gas flow rate, air gas flow rate and long-term operation on the H(2)S removal efficiency was investigated. In addition, the comparative performance of sulfide oxidizing bacterium immobilized on GAC (biofilter A) and GAC without cell immobilization (biofilter B) systems was studied. It was found that the efficiency of the H(2)S removal was more than 98% even at high concentrations (200-4000 ppm) and the maximum elimination capacity was about 125 g H(2)S/m(3)of GAC/h in the biofilter A. However, the H(2)S flow rate of 15-35 l/h into both biofilters had little influence on the efficiency of H(2)S removal. Moreover, an air flow rate of 5.86 l/h gave complete removal of H(2)S (100%) in biofilter A. During the long-term operation, the complete H(2)S removal was achieved after 3-days operation in biofilter A and remained stable up to 60-days.

Upflow bio-filter circuit (UBFC): biocatalyst microbial fuel cell (MFC) configuration and application to biodiesel wastewater treatment.

A biodiesel wastewater treatment technology was investigated for neutral alkalinity and COD removal by microbial fuel cell. An upflow bio-filter circuit (UBFC), a kind of biocatalyst MFC was renovated and reinvented. The developed system was combined with a pre-fermented (PF) and an influent adjusted (IA) procedure. The optimal conditions were operated with an organic loading rate (OLR) of 30.0 g COD/L-day, hydraulic retention time (HRT) of 1.04 day, maintained at pH level 6.5-7.5 and aerated at 2.0 L/min. An external resistance of circuit was set at 10 kΩ. The purposed process could improve the quality of the raw wastewater and obtained high efficiency of COD removal of 15.0 g COD/L-day. Moreover, the cost of UBFC system was only US

Removal of hydrogen sulfide generated during anaerobic treatment of sulfate-laden wastewater using biochar: Evaluation of efficiency and mechanisms

1775.7/m3 and the total power consumption was 0.152 kW/kg treated COD. The overall advantages of this invention are suitable for biodiesel wastewater treatment.

Mitigation of carbon dioxide by oleaginous microalgae for lipids and pigments production: Effect of light illumination and carbon dioxide feeding strategies.

Removal of hydrogen sulfide (H2S) from biogas was investigated in a biochar column integrated with a bench-scale continuous-stirred tank reactor (CSTR) treating sulfate-laden wastewater. Synthetic wastewater containing sulfate concentrations of 200-2000mg SO42-/L was used as substrate, and the CSTR was operated at an organic loading rate of 1.5g chemical oxygen demand (COD)/L·day and a hydraulic retention time (HRT) of 20days. The biochar was able to remove about 98.0 (±1.2)% of H2S for the ranges of concentrations from 105-1020ppmv, especially at high moisture content (80-85%). Very high H2S adsorption capacity (up to 273.2±1.9mg H2S/g) of biochar is expected to enhance the H2S oxidation into S0 and sulfate. These findings bring a potentially novel application of sulfur-rich biochar as a source of sulfur, an essential but often deficient micro-nutrient in soils.

Optimization of flocculation efficiency of lipid-rich marine Chlorella sp. biomass and evaluation of its composition in different cultivation modes

Oleaginous microalgae Nannochloropsis sp. was selected as potential strain for CO2 mitigation into lipids and pigments. The synergistic effects of light intensity and photoperiod were evaluated to provide the adequate light energy for this strain. The saturation light intensity was 60μmol·photon·m(-2)s(-1). With full illumination, the biomass obtained was 0.850±0.16g·L(-1) with a lipid content of 44.7±1.2%. The pigments content increased with increasing light energy supply. Three main operating factors including initial cell concentration, CO2 content and gas flow rate were optimized through Response Surface Methodology. The feedings with low CO2 content at high gas flow rate gave the maximum biomass but with low lipid content. After optimization, the biomass and lipid production were increased up to 1.30±0.103g·L(-1) and 0.515±0.010g·L(-1), respectively. The CO2 fixation rate was as high as 0.729±0.04g·L(-1)d(-1). The fatty acids of Nannochloropsis sp. lipids were mainly C16-C18 indicating its potential use as biodiesel feedstocks.

Hydrogen Sulfide Removal from Biogas Using Pure and Mixed Cultures of Sulfide-Oxidizing Bacteria Biofiltration

This study aimed to optimize flocculation efficiency of lipid-rich marine Chlorella sp. biomass and evaluate its composition in different cultivation modes. Among three flocculants including Al(3+), Mg(2+) and Ca(2+) tested, Al(3+) was most effective for harvesting microalgal biomass. Four important parameters for flocculation were optimized through response surface methodology. The maximum flocculation efficiency in photoautotrophic culture was achieved at pH 10, flocculation time of 15 min, Al(3+) concentration of 2.22 mM and microalgal cells of 0.47 g/L. The flocculation in mixotrophic culture required lower amount of Al(3+) (0.74 mM) than that in photoautotrophic and heterotrophic cultures (2.22 mM). The biomass harvested from mixotrophic culture contained lipid at the highest content of 42.08 ± 0.58% followed by photoautotrophic (32.08 ± 3.88%) and heterotrophic (30.42 ± 1.13%) cultures. The lipid-extracted microalgal biomass residues (LMBRs) contained protein as high as 38-44% and several minerals showing their potential use as animal feed and their carbohydrate content were 16-29%.

Effect of pH, OLR, and HRT on performance of acidogenic and methanogenic reactors for treatment of biodiesel wastewater

A novel biofiltration system using pure and mixed cultures of sulfide-oxidizing bacteria immobilized on granular activated carbon (GAC) to purify synthetic and real biogas from a sulfate reaction reactor of concentrated latex industry, contaminated by H2S, was studied. Complete H2S removal from synthetic biogas was found in pure and mixed culture reactors at 200 ppm initial H2S concentration, 35 l h−1 of biogas flow rate and 5.83 l h−1 of airflow rate. H2S removal using biofiltration had little effect on the methane content of synthetic biogas. Pure and mixed culture reactors at airflow rates of 0.75–5.83 l h−1 also showed complete H2S removal from real biogas. However, H2S removal efficiency at the airflow rate of 0.53 l h−1 decreased to 99%. Thus, H2S removal using biofiltration had little effect on the methane content of real biogas. The results of this study suggest the feasibility of developing using mixed culture of sulfide-oxidizing bacteria from concentrated latex wastewater for industrial application to remove H2S from biogas through biofiltration.

Effect of organic loading rate on methane and volatile fatty acids productions from anaerobic treatment of palm oil mill effluent in UASB and UFAF reactors

AbstractTwo-stage anaerobic process was studied in order to treat biodiesel wastewater. The first stage represented acidogenic reactor while the second stage was methanogenic reactor. The effect of pH, hydraulic retention time (HRT), and organic loading rate (OLR) on performance of both reactors was investigated. The optimum condition was examined using response surface methodology with the Box–Behnken Design. In the acidogenic reactor, the optimum pH, HRT, and OLR were 6.48, 16 h, and 26 g COD/(l d), respectively. High VFA production of 9.35 g/l was achieved with the low methane production. In the methanogenic reactor, the optimum pH, HRT, and OLR were 6.95, 30 h, and 6 g COD/(l d), respectively. Biogas production of 19.1 l/d was obtained with the methane content of 66%. VFA was completely consumed. In comparison, the two-stage system showed higher efficiency (COD removal, biogas production, and methane yield) than the one-stage system.