Cultivation of Chlorella vulgaris in Column Photobioreactor for Biomass Production and Lipid Accumulation.

Microalgae have been used as energy resources in recent decades to mitigate the global energy crisis. As the demand for pure microalgae strains for commercial use increases, designing an effective photobioreactor (PBR) for mass cultivation is important. Chlorella vulgaris, a local freshwater microalga, was used to study the algal biomass cultivation and lipid production using various PBR configurations (bubbling, air-lift, porous air-lift). The results show that a bubbling column design is a better choice for the cultivation of Chlorella vulgaris than an air-lift one. The highest biomass concentration in the bubbling PBR was 0.78 g/L while the air-lift PBR had a value of 0.09 g/L. Key operating parameters, including draft-tube length and bubbling flowrate, were then optimized based on biomass production and lipid yield. The highest lipid content was in the porous air-lift PBR and the air-lift PBR with shorter draft tube (35 cm) was also better than a longer one (50 cm) for algal cultivation, but the microalgae attachment on the inner tube of PBR always occurred. The highest biomass concentration could be produced under the highest gas flowrate of 2.7 L/min, whereas the lowest dry cell mass was under the lowest gas flowrate of 0.2 L/min.

Scenedesmus quadricauda for Nutrient Removal and Lipid Production in Wastewater.

Scenedesmus quadricauda, a local freshwater microalga, was used to treat primary settled and filtrate wastewater and to produce algal lipid. For the primary settled wastewater, the maximum biomass concentrations of acclimated and unacclimated microalgae were 0.995 g/L and 0.940 g/L, respectively. Over 90% orthophosphate and 95% ammonia nitrogen in the acclimated and unacclimated cultures, respectively, were removed after five days. The lipid contents of the microalgae were higher than 13% in all cultures. The highest growth rate occurred in the 25% filtrate culture. Over 80% phosphate was removed under the 25% and 50% filtrate cultures within six days, while over 90% ammonia nitrogen was removed within five days under both conditions. The lipid content was the highest (18.1%) under the 50% filtrate condition. C16:0, C18:2n6, and C18:3n3 were dominant fatty acids. In conclusion, S. quadricauda is a viable candidate for wastewater treatment and lipid production.

Nocardia foaming control in activated sludge process treating domestic wastewater.

In this study, filamentous bacteria (Nocardia amarae) were identified as the major causal microorganism in foaming sludge. The results of growth kinetics study indicated that N. amarae had a relatively strong affinity for non-readily biodegradable fatty acids. N. amarae was able to consume various fatty acids at a constant growth yield from 0.413 to 0.487 g/gCOD. Under common F/M ratio (less than 0.5 g BOD/gMLSS/d) used in activated sludge processes, specific growth rate of N. amarae was found to be more significant than that of non-filamentous bacteria. Based on this feature, a novel technique feast-fast operation (FFO) was developed for the foaming control. The sludge volume index (SVI) rapidly decreased from 300 to 80 mL/g and further stabilized at about 70 mL/g and the system was free from stable foam, while the BOD removal efficiency was maintained above 95%. This control technology effectively suppressed the overgrowth of filaments and improved the settleability of activated sludge without adverse effects on the treatment performance and the process stability.

Treatment of odorous volatile fatty acids using a biotrickling filter.

In this study, a novel fibrous bioreactor was developed for treating odorous compounds present in contaminated air. The first stage of this work was a preliminary study which aimed at investigating the feasibility of using the fibrous bioreactor for the removal of malodorous volatile fatty acids (VFA) that is a common odorous contaminant generated from anaerobic degradation of organic compounds. The kinetics of microbial growth and VFA degradation in the selected culture, and the performance of the submerged bioreactor at different VFA mass loadings were studied. Above 95% of VFA removal efficiencies were achieved at mass loadings up to 22.4 g/m(3)/h. In the second stage, the odour treatment process was scaled up with system design and operational considerations. A trickling biofilter with synthetic fibrous packing medium was employed. The effects of inlet VFA concentration and empty bed retention time (EBRT) on the process performance were investigated. The bioreactor was effective in removing VFA at mass loadings up to 32 g/m(3)/h, beyond which VFA started to accumulate in the recirculation liquid, indicating the biofilm was unable to degrade all of the VFA introduced. Although VFA accumulated in the liquid phase, the removal efficiency remained above 99%. This suggested that the biochemical reaction rather than gas-liquid mass transfer was the limiting step of the treatment process. In addition, the biotrickling filter was stable for long-term operation with relatively low and steady pressure drop, no clogging and degeneration of the packing material occurred during the four-month study.

Performance study of vegetated sequencing batch coal slag bed treating domestic wastewater in suburban area.

A practical and affordable wastewater treatment system serving small community in suburban areas was studied. The system was a vegetated sequencing batch coal slag bed integrated with the rhythmical movement of wastewater and air like that of a sequencing batch reactor. The removal mechanisms capitalized on the pollutant removal process in conventional constructed wetland. Cyperus alternifolius was planted into the coal slag bed to form a novel plant-soil-microbial interactive system. Nutrients in the domestic wastewater, which cause environmental nuisance like eutrophication, were targeted to be eliminated by the process design. Operated with the contact time of 18 h, the treatment systems achieved around 60% removal efficiency for carbonaceous matters. The removals of ammonia nitrogen and phosphorus were about 50% and 40%, respectively, while the removal of total suspended solids was approaching 80%. From the current study, the construction cost of the vegetated sequencing batch coal slag bed was 256 RMB/m3 and the operation cost was 0.13 RMB/m3. With the advantages of ease of operation, low costs, desirable treatment efficiency and aesthetic value, the vegetated sequencing batch coal slag bed is proposed to be an alternative for onsite domestic wastewater treatment in suburban areas.

Assessing optimal fermentation type for bio-hydrogen production in continuous-flow acidogenic reactors.

In this study, the optimal fermentation type and the operating conditions of anaerobic process in continuous-flow acidogenic reactors was investigated for the maximization of bio-hydrogen production using mixed cultures. Butyric acid type fermentation occurred at pH>6, propionic acid type fermentation occurred at pH about 5.5 with E(h) (redox potential) >-278mV, and ethanol-type fermentation occurred at pH<4.5. The representative strains of these fermentations were Clostridium sp., Propionibacterium sp. and Bacteriodes sp., respectively. Ethanol fermentation was optimal type by comparing the operating stabilities and hydrogen production capacities between the fermentation types, which remained stable when the organic loading rate (OLR) reached the highest OLR at 86.1kgCOD/m(3)d. The maximum hydrogen production reached up to 14.99L/d.

Synthesis of PHAs from waster under various C:N ratios.

Polyhydroxyalkanoates (PHAs) production was carried out under various C:N ratios. A ratio of 100 resulted best polymer yield. C-source was an important factor in synthesis. For example, as the ratio of valeric acid (C5) to butyric acid (C4) in N-free medium was increased, the mole fraction of HV in the copolymer increased. When soy waste was used as a C-source a copolymer, a high HV mole fraction (HB:HV, 75:25) was produced while when malt waste was used, a much lower HV mole fraction (HB:HV, 90:10) was generated. It was concluded that activated sludge bacteria could be induced to produce PHAs using food wastes as C-sources and this could be the basis for production of biodegradable plastics.

The influence of foot-shock stress upon brain, pituitary and spinal cord pools of immunoreactive dynorphin in rats.

The distribution of immunoreactive-dynorphin (ir-dyn) in the pituitary, discrete regions of brain and the spinal cord, and the influence of 5 min foot-shock stress (FS) upon levels of ir-dyn in these structures, were examined in rats. FS produced a significant fall in the anterior pituitary lobe (AL) content of ir-dyn but no significant change in its neurointermediate (NIL) counterpart. In the hypothalamus, in contrast, a significant elevation in levels of ir-dyn was observed. With the exception of the frontal cortex, in which a decrease in levels of ir-dyn was found, in all other brain regions examined no significant changes emerged. A significant diminution in concentrations of ir-dyn in both the lumbosacral and thoracic sections of the spinal cord was, however, detected.

Response of brain and pituitary pools of dynorphin as compared to vasopressin to acute stress in the rat.

5 min foot-shock resulted in an elevation in levels of immunoreactive (ir)-dynorphin (DYN) and ir-vasopressin (VP) in the hypothalamus whereas their levels were not significantly modified in the neurointermediate pituitary. In the anterior pituitary, however, a fall in ir-DYN in the absence of any change in ir-VP was detected. Further, in the thalamus and medulla/pons, respectively, a decrease and increase in levels of ir-VP was observed whilst the content of ir-DYN therein was not significantly affected. These findings support the concept of a common origin and co-modulation of DYN and VP in the hypothalamic-neural lobe axis and that, extrinsic to this, DYN and VP are localized and modulated independently of each other.

Evidence for the existence of meta and para directing O-methyltransferases in tobacco cell cultures.

The O-methyltransferase of tobacco cell culture was resolved to its meta and para directing forms by chromatography on DEAE-cellulose. Despite similarities in molecular weights and pI values of the two forms, however, evidence from pH optima, SH-group inhibitors, methylation ratios, SDS-acrylamide gels and mixed substrate experiments indicates the existence of two discrete enzymes acting at the meta and para positions of caffeic acid and quercetin, respectively; though the latter enzyme was less substrate specific than its meta counterpart.