[Show abstract][Hide abstract] ABSTRACT: Piggery wastewater is a potent nutrient source for microalgal lipid production. Wastewater has been usually sterilized when used for microalgal cultivation. This is uneconomical in large-scale applications. Therefore, lipid productivity of Chlorella vulgaris CY5 using sterilized and non-sterilized diluted anaerobically pretreated piggery wastewater was studied in batch reactors. The maximum average lipid productivity was obtained after 12 days of incubation and it was higher with the sterilized wastewater than with the non-sterilized one (117 g/L/d vs. 91.3 g/L/d), due to the higher biomass concentration. Because of the unexpected increase of dissolved organic carbon (DOC) in the cultures, second experiment was conducted to characterize the composition of produced DOC in non-sterilized wastewater. Carbohydrate content increased in the liquid phase but decreased in the biomass after nitrogen had been exhausted. After 12 days of incubation, soluble chemical oxygen demand (CODs) was 414 ± 56 mg/L, biomass production was 2.8 ± 0.15 g/L, and lipid content was 30.3 ± 1.2 wt%. Average lipid productivity from day zero to day 12 was 70.5 ± 1.1 g/L/d. C. vulgaris removed nutrients from the non-sterilized wastewater and produced oleaginous biomass, although the lipid productivity was higher with sterilized wastewater.
[Show abstract][Hide abstract] ABSTRACT: Microalgae can be used as a biological photocatalyst to reduce the CO 2 levels in the atmosphere, with the advantage of not competing with food crops for arable land, and thus offer a potential method for limiting climate change. Microalgae have also been proposed as a sustainable fuel source. This study investigated the microalgae harvest yields, the thermogravimetric behavior of both microalgae oil and microalgae residue, the torrefaction of microalgae residue, and diesel engine tests using diesel-microalgae biodiesel blends. The mean annual harvest rate of microalgae oil in open ponds was found to be 4355 kg per 10000 m
Aerosol and Air Quality Research 02/2015; 15(1):81-98. DOI:10.4209/aaqr.2014.10.0268 · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study investigated methanogenic communities involved in degradation of tetramethylammonium hydroxide (TMAH) in three full-scale bioreactors treating TMAH-containing wastewater. Based on the results of terminal-restriction fragment-length polymorphism (T-RFLP) and quantitative PCR analyses targeting the methyl-coenzyme M reductase alpha subunit (mcrA) genes retrieved from three bioreactors, Methanomethylovorans and Methanosarcina were the dominant methanogens involved in the methanogenic degradation of TMAH in the bioreactors. Furthermore, batch experiments were conducted to evaluate mcrA messenger RNA (mRNA) expression during methanogenic TMAH degradation, and the results indicated that a higher level of TMAH favored mcrA mRNA expression by Methansarcina, while Methanomethylovorans could only express considerable amount of mcrA mRNA at a lower level of TMAH. These results suggest that Methansarcina is responsible for methanogenic TMAH degradation at higher TMAH concentrations, while Methanomethylovorans may be important at a lower TMAH condition.
[Show abstract][Hide abstract] ABSTRACT: This study presented an approach by combining the real-time reverse transcription polymerase chain reaction with the terminal restriction fragment length polymorphism (T-RFLP) to investigate transcriptional responses of ammonia-oxidizing bacteria (AOB) to dimethyl sulfide (DMS) inhibition. Batch experiments with added ammonium and DMS were conducted using three activated sludges and Nitrosomonas europaea, and the transcriptional responses of the amo subunit A (amoA) mRNA were evaluated. It was found that DMS inhibited ammonium oxidation and amoA mRNA expression in all batch experiments but the inhibition degree observed was different for different sludges examined. It is likely that the different inhibitory effects of DMS on ammonium oxidation and amoA mRNA expression stemmed from different dominant AOB populations in the sludges. The T-RFLP results for amoA mRNA suggested that inhibition of ammonium oxidation by DMS to Nm. europaea-like AOB with T-RF 219/270 is relatively minor compared to other AOB populations in the examined sludges, such as Nm. europaea-like AOB with T-RF 491/491.
[Show abstract][Hide abstract] ABSTRACT: This study applies metabolic flux network analysis (MFA) to evaluate the metabolic flux of fermentative hydrogen production (FHP) with the use of Clostridium tyrobutyricum fed with either glucose or lactate/acetate as substrates. The MFA results suggest that hydraulic retention time (HRT) presents significant impact on hydrogen production from glucose. At HRT between 4 and 18h, increase of HRT increased hydrogen production but decreased lactate production, while at HRT below 4h decrease of HRT increased hydrogen production but decreased lactate production. The flux for lactate, butyrate and acetate seemed to affect H2 production, due presumably to their impacts on the balance of NADH, ferredoxin and ATP. It is suggested that the MFA can be a useful tool to provide valuable information for optimization and design of the fermentative hydrogen production process.
[Show abstract][Hide abstract] ABSTRACT: This study investigated the linkage between performance of two full-scale membrane bioreactor (MBR) systems treating thin-film transistor liquid crystal display (TFT-LCD) wastewater and the population dynamics of dimethylsulfoxide (DMSO)/dimethylsulfide (DMS) degrading bacteria. High DMSO degradation efficiencies were achieved in both MBRs, while the levels of nitrification inhibition due to DMS production from DMSO degradation were different in the two MBRs. The results of real-time PCR targeting on DMSO/DMS degrading populations, including Hyphomicrobium and Thiobacillus spp., indicated that a higher DMSO oxidation efficiency occurred at a higher Hyphomicrobium spp. abundance in the systems, suggesting that Hyphomicrobium spp. may be more important for complete DMSO oxidation to sulfate compared with Thiobacillus spp. Furthermore, Thiobacillus spp. was more abundant during poor nitrification, while Hyphomicrobium spp. was more abundant during good nitrification. It is suggested that microbial population of DMSO/DMS degrading bacteria is closely linking to both DMSO/DMS degradation efficiency and nitrification performance.
[Show abstract][Hide abstract] ABSTRACT: This study investigated impact of food to microorganism (F/M) ratio and colloidal chemical oxygen demand (COD) on nitrification performance in one full-scale membrane bioreactor (MBR) treating monoethanolamine (MEA)/dimethyl sulfoxide (DMSO)-containing thin film transistor liquid crystal display (TFT-LCD) wastewater. Poor nitrification was observed under high organic loading and high colloidal COD conditions, suggesting that high F/M ratio and colloidal COD situations should be avoided to minimize their negative impacts on nitrification. According to the nonmetric multidimensional scaling (NMS) statistical analyses on terminal restriction fragment length polymorphism (T-RFLP) results of ammonia monooxygenase (amoA) gene, the occurrence of Nitrosomonas oligotropha-like ammonia oxidizing bacteria (AOB) was positively related to successful nitrification in the MBR systems, while Nitrosomonas europaea-like AOB was positively linked to nitrification rate, which can be attributed to the high influent total nitrogen condition. Furthermore, Nitrobacter- and Nitrospira-like nitrite oxidizing bacteria (NOB) were both abundant in the MBR systems, but the continuously low nitrite environment is likely to promote the growth of Nitrospira-like NOB.
[Show abstract][Hide abstract] ABSTRACT: The diversity and abundance of ammonia-oxidizing Betaproteobacteria and archaea were investigated in a full-scale municipal wastewater treatment plant where the wastewater conductivity level varied considerably (due to seawater salinity intrusion) during this study between 2004 and 2007. Based on the quantitative polymerase chain reaction of ammonia monooxygenase subunit A (amoA) genes, an increase in the ammonia oxidizing bacteria amoA gene copies occurred with a decrease in the wastewater salinity level. A corresponding decrease in the average ammonia-oxidizing archaea to bacteria ratio, from 1.22 (2004 and 2005), 0.17 (2006), and then to 0.07 (2007), was observed. Phylogenetic analyses on amoA gene sequences indicated that Nitrosomonas marina-like ammonia oxidizing bacteria and Thaumarcheota Ⅰ.1a (marina group) ammonia-oxidizing archaea were dominant when the wastewater salinity level fluctuated at high values with an average of 4.83 practical salinity unit (psu), while Nitrosomonas urea-like ammonia oxidizing bacteria and Thaumarcheota Ⅰ.1b (soil group) ammonia-oxidizing archaea became dominant when the wastewater salinity decreased to a more stable lower level with an average of 1.93 psu. Based on the amoA gene-based terminal restriction fragment length polymorphism analyses, results from this study demonstrated that the observed shift in ammonia oxidizing bacteria and archaea populations is likely caused by a change of the wastewater salinity level.
Journal of Bioscience and Bioengineering 12/2012; 115(4). DOI:10.1016/j.jbiosc.2012.11.005 · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study examined the hypothesis that different inorganic carbon (IC) conditions enrich different ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) populations by operating two laboratory-scale continuous-flow bioreactors fed with 15 and 100 mg IC/L, respectively. During this study, both bioreactors maintained satisfactory nitrification performance and stably oxidized 250 mg N/L of influent ammonium without nitrite accumulation. Based on results of cloning/sequencing and terminal restriction fragment length polymorphism targeting on the ammonia monooxygenase subunit A (amoA) gene, Nitrosomonas nitrosa lineage was identified as the dominant AOB population in the high-IC bioreactor, while Nitrosomonas europaea and Nitrosomonas nitrosa lineage AOB were dominant in the low-IC bioreactor. Results of real-time polymerase chain reactions for Nitrobacter and Nitrospira 16S rRNA genes indicated that Nitrospira was the predominant NOB population in the high-IC bioreactor, while Nitrobacter was the dominant NOB in the low-IC bioreactor. Furthermore, batch experiment results suggest that N. europaea and Nitrobacter populations are proliferated in the low-IC bioreactor due to their higher rates under low IC conditions despite the fact that these two populations have been identified as weak competitors, compared with N. nitrosa and Nitrospira, under low ammonium/nitrite environments. This study revealed that in addition to ammonium/nitrite concentrations, limited IC conditions may also be important in selecting dominant AOB/NOB communities of nitrifying bioreactors.
[Show abstract][Hide abstract] ABSTRACT: This study investigated nitrification performance and nitrifying community in one full-scale membrane bioreactor (MBR) treating TFT-LCD wastewater. For the A/O MBR system treating monoethanolamine (MEA) and dimethyl sulfoxide (DMSO), no nitrification was observed, due presumably to high organic loading, high colloidal COD, low DO, and low hydraulic retention time (HRT) conditions. By including additional A/O or O/A tanks, the A/O/A/O MBR and the O/A/O MBR were able to perform successful nitrification. The real-time PCR results for quantification of nitrifying populations showed a high correlation to nitrification performance, and can be a good indicator of stable nitrification. Terminal restriction fragment length polymorphism (T-RFLP) results of functional gene, amoA, suggest that Nitrosomonas oligotropha-like AOB seemed to be important to a good nitrification in the MBR system. In the MBR system, Nitrobacter- and Nitrospira-like NOB were both abundant, but the low nitrite environment is likely to promote the growth of Nitrospira-like NOB.
[Show abstract][Hide abstract] ABSTRACT: This study evaluated biological treatment of TMAH in a full-scale methanogenic up-flow anaerobic sludge blanket (UASB) followed by an aerobic bioreactor. In general, the UASB was able to perform a satisfactory TMAH degradation efficiency, but the effluent COD of the aerobic bioreactor seemed to increase with an increased TMAH in the influent wastewater. The batch test results confirmed that the UASB sludge under methanogenic conditions would be favored over the aerobic ones for TMAH treatment due to its superb ability of handling high strength of TMAH-containing wastewaters. Based on batch experiments, inhibitory chemicals present in TFT-LCD wastewater like surfactants and sulfate should be avoided to secure a stable methanogenic TMAH degradation. Finally, molecular monitoring of Methanomethylovorans hollandica and Methanosarcina mazei in the full-scale plant, the dominant methanogens in the UASB responsible for TMAH degradation, may be beneficial for a stable TMAH treatment performance.
[Show abstract][Hide abstract] ABSTRACT: In this study, a continuous-flow stirred tank reactor (CSTR) fed with lactate and acetate was operated to enrich hydrogen-producing bacteria. By varying the influent substrate concentrations and hydraulic retention times (HRT), the volumetric loading rate (VLR) of 55.64 kg-COD/m(3)/day seemed to be optimum for this enriched culture for fermentative hydrogen production from lactate and acetate. The results of batch experiments confirmed that the enriched culture tended to fulfill the e(-) equiv requirement for cell growth at a lower VLR condition (21.77 kg-COD/m(3)/day), while it could largely distribute the e(-) equiv for hydrogen production at a higher VLR condition. However, a maximum lactate/acetate concentration allowed for enriching this culture existed, especially at a lower HRT condition in which wash-out can be an issue for this enriched culture. Finally, the results of cloning and sequencing indicated that Clostridium tyrobutyricum was considered the major hydrogen-producing bacteria in the CSTR fed with lactate and acetate.
[Show abstract][Hide abstract] ABSTRACT: This study evaluates a two-stage bioprocess for recovering hydrogen and methane while treating organic residues of fermentative bioethanol from rice straw. The obtained results indicate that controlling a proper volumetric loading rate, substrate-to-biomass ratio, or F/M ratio is important to maximizing biohydrogen production from rice straw bioethanol residues. Clostridium tyrobutyricum, the identified major hydrogen-producing bacteria enriched in the hydrogen bioreactor, is likely utilizing lactate and acetate for biohydrogen production. The occurrence of acetogenesis during biohydrogen fermentation may reduce the B/A ratio and lead to a lower hydrogen production. Organic residues remained in the effluent of hydrogen bioreactor can be effectively converted to methane with a rate of 2.8 mmol CH(4)/gVSS/h at VLR of 4.6 kg COD/m(3)/d. Finally, approximately 75% of COD in rice straw bioethanol residues can be removed and among that 1.3% and 66.1% of COD can be recovered in the forms of hydrogen and methane, respectively.
[Show abstract][Hide abstract] ABSTRACT: The effect of supplementary carbon addition for the treatment of high-technology industrial wastewater in a membrane bioreactor (MBR) was investigated. The MBR was operated for 302 days under different C/N (BOD(L)/NH(4)(+)-N) ratios, i.e. 0.9-1 to 20 days, 1.6-21 to 42 days, 2.9-43 to 82 days, 3.6-83 to 141 days, 4.8-165 to 233 days and 9.3-240 to 302 days. Irrespective of the C/N ratios investigated, SS and BOD(5) removal efficiencies were above 95% and above 80% COD removal efficiency was observed. In addition, complete nitrification was observed throughout the investigation. However, denitrification and total nitrogen removal efficiencies reached their maximum values at the highest C/N ratio (9.3) investigated. Real-time PCR analysis revealed 10 times higher ammonia oxidizing bacteria to total bacteria ratio under the highest C/N ratio condition (9.3) compared to the low C/N ratio condition (1.6).
[Show abstract][Hide abstract] ABSTRACT: Biodegradation of petroleum hydrocarbon oil (14,000 mg kg−1) were investigated in six biopiles batches, differing in the remediation strategy: bioaugmentation (selected consortium and kitchen waste were introduced), biostimulation (added with rhamnolipid, high-level, or low-level nutrient), and bioaugmentation plus biostimulation (added both with rhamnolipid and bacterial consortia). After the 140-day operation, the kitchen waste (KW) and the low-level nutrient (NEL) batches achieved the highest total petroleum hydrocarbon degradation efficiency (>80%). The result of the hydrocarbon analysis revealed that the bioaugmentation approaches were the most effective ones in removing aromatic component (64% and 68%), and KW and NEL were the only two approaches that can remove the polar component with positive efficiency, 11% and 21%, respectively. The terminal-restriction fragment length polymorphism percentage (T-RFLP) abundance applied with nonmetric multidimensional scaling indicated a similarity of the bacterial communities during the early fastest remediation stage. The results of the oligonucleotide array targeting the ribosomal internal transcribed spacer (ITS) region, along with the hydrocarbon fractional analysis, indicated a successive degradation completed by the bacterial–fungi consortia. Before Day 70, the bacterial community was dominant in decomposing the saturated and partially aromatic hydrocarbons. After Day 70, the fungal community found to be dynamic and responsible for degradation of the polar hydrocarbons composing of recalcitrant metabolites.
[Show abstract][Hide abstract] ABSTRACT: A custom-made atmospheric argon micro-plasma system was employed to dissociate dimethyl sulfide (DMS) into a non-foul-smelling species. The proposed system takes the advantages of low energy requirement and non-thermal process with a constant flow rate at ambient condition. In the experiments, the compositions of DMS/argon plasma, the residual gaseous phases, and solid precipitates were respectively characterized using an optical emission spectrometer, various gas-phase analyzers, and X-ray photoemission spectroscopy. For 400 ppm DMS introduced into argon plasma with two pairs of electrodes (90 W), a complete decomposition of DMS was achieved; the DMS became converted into excited species such as C, C(2), H, and CH. When gaseous products were taken away from the treatment area, the excited species tended to recombine and form stable compounds or species, which formed as solid particles and gaseous phases. The solid deposition was likely formed by the agglomeration of C-, H-, and S-containing species that became deposited on the quartz inner tube. For the residual gaseous phases, low-molecular-weight segments mostly recombined into relatively thermodynamic stable species, such as hydrogen, hydrogen sulfide, and carbon disulfide. The dissociation mechanism and treatment efficiency are discussed, and a treatment of converting DMS into H(2)-, CS(2)-, and H(2)S-dominant by-products is proposed.
[Show abstract][Hide abstract] ABSTRACT: The materials and energy in an integrated biological hydrogen production and purification system involving hydrolysis, dark fermentation, photo fermentation, CO2 fixation and anaerobic digestion are balanced by integrating the results from multiple experiments, simulations and the literature. The findings are two fold. First, using 1000 kg rice straw as a substrate, 19.8 kg H2 and 138.0 kg CH4 are obtained. The net energy balance (NEB) and net energy ratio (NER) are -738.4 kWh and 77.8%, respectively, both of which imply an unfavorable energy production system. Opportunities to improve the performance particularly lie in the photo fermentation process. Second, greenhouse gas emissions are evaluated for various options. The results were comparable with the emission inventory of electricity generated from fossil fuels. NEB and NER under a zero-carbon-emission constraint were discussed in detail to clarify completely the implications of the energy and material balances on greenhouse gas emissions.
[Show abstract][Hide abstract] ABSTRACT: This study evaluates the microbial metabolism and energy demand in fermentative biohydrogen production using Clostridium tyrobutyricum FYa102 at different hydraulic retention times (HRT) over a period of 1-18 h. The hydrogen yield shows a positive correlation with the butyrate yield, the B/A ratio, and the Y(H2)/2(Y(HAc)+Y(HBu)) ratio, but a negative correlation with the lactate yield. A decrease in HRT, which is accompanied by an increased biomass growth, tends to decrease the B/A ratio, due presumably to a higher energy demand for microbial growth. The production of lactate at a low HRT, however, may involve an unfavorable change in e(-) equiv distribution to result in a reduced hydrogen production. Finally, the relatively high hydrogen yields observed in the bioreactor with the peptone addition may be ascribed to the utilization of peptone as an additional energy and/or amino-acid source, thus reducing the glucose demand for biomass growth during the hydrogen production process.