Heavy metal control in microalgae cultivation with power plant flue gas entering into raceway pond.

The heavy metal sources of large-scale raceway pond microalgae cultivation with flue gas were investigated to reduce heavy metal contents in microalgae during cultivation. The microalgae were cultivated with power plant flue gas (as C source) and circulating cooling seawater (added with N and P nutrients) for 6 days. The Pb, Cd, Hg, and As contents in microalgae were 0.91, 0.22, 0.08, and 0.28 ppm, respectively, which are nearly within the available national standard for food-grade microalgae. The heavy metal contents in microalgae with two membrane materials, namely, elastic polyethylene and random copolymer polypropylene, barely increased. The Hg, As, and Pb contents in microalgae cells cultivated with pure CO2 were 16.67%, 69.23%, and 70.33% that of cells cultivated with CO2 from flue gas. The Pb, As, and Hg contents in cells cultivated with fresh water were reduced by 38.46%, 15.38%, and 37.50%, respectively, compared with those cultivated with seawater. The heavy metal contents in microalgae were further reduced and controlled.

Effects of acupuncture on breast cancer-related lymphoedema: A systematic review and meta-analysis.

BACKGROUND: Lymphoedema is a common complication of axillary dissection surgery, especially for breast cancer patients. Approximately 20% of breast cancer survivors develop breast cancer-related lymphoedema (BCRL). Acupuncture (AC) has become an alternative treatment for BCRL. In this study, we investigated whether AC was a good method for treating limb oedema in women after breast cancer surgery. METHODS: We performed a systematic review and meta-analysis of published randomized controlled trials (RCTs) to evaluate the effectiveness of AC in the prevention of BCRL. Searching strategies were performed with the following keywords: "Breast cancer," "Acupuncture," "neoplasm," and "lymphoedema," with derivations and different combinations of these keywords. The following databases were searched: PubMed, Cochrane Library, EMBASE, Web of Science, CNKI, WanFang, and CBM. Studies published in English and Chinese were considered for inclusion in this study. Study selection, risk of bias assessment and data extraction were independently conducted. Statistical analyses were conducted with RevMan software (version 5.3). RESULTS: Eight studies were identified by the search strategy, and 519 patients were included in this study. The effective rate was higher (odds ratios (OR): 4.23; 95% confidence interval (CI): 2.11 to 8.49; Z = 4.07, p < 0.0001) in the experimental group than that in the control group. There were no significant improvements in the front flexion (mean difference (MD): 0.19; 95% CI: -3.68 to 4.06; Z = 0.09, p = 0.92) or the back extension (MD: 0.42; 95% CI: -2.22 to 3.06; Z = 0.31, p = 0.75) movements of the shoulder between the experimental and control groups. CONCLUSIONS: AC may be an effective method for improving the condition of breast cancer-related lymphoedema. However, due to the high risk of bias and the low quality of the available studies, further high-quality RCTs are needed to confirm the efficacy of AC for breast cancer-related lymphoedema patients.

Improving microalgal growth by strengthening the flashing light effect simulated with computational fluid dynamics in a panel bioreactor with horizontal baffles.

Biological CO2 elimination by photosynthetic microalgae is a sustainable way to mitigate CO2 from flue gas and other sources. Computational fluid dynamics was used to simulate algal cell movement with an enhanced flashing light effect in a novel panel bioreactor with horizontal baffles. Calculation results showed that the light/dark (L/D) cycle period decreased by 17.5% from 17.1 s to 14.1 s and that the horizontal fluid velocity increased by 95% while horizontal baffles were used under a 0.02 vvm air aeration rate and a microalgal concentration of 0.85 g L-1. The probability of the L/D cycle period within 5-10 s increased from 27.9% to 43.6%, indicating a 56% increase when horizontal baffles existed. It was proved by experiments that the mass-transfer coefficient increased by 31% and the mixing time decreased by 13% under a 0.06 vvm air aeration rate when horizontal baffles were used, and the algal biomass yield increased by ∼51% along with the decrease in the L/D cycle period when horizontal baffles were used.

Microstructure and antioxidative capacity of the microalgae mutant Chlorella PY-ZU1 during tilmicosin removal from wastewater under 15% CO2.

The response mechanisms of microalgal mutant Chlorella PY-ZU1 cells were investigated in their removal of antibiotic tilmicosin from wastewater under 15% CO2. Low concentrations (0.01-2mgL-1) of tilmicosin in wastewater stimulated the growth of microalgal cells, whereas high concentrations (5-50mgL-1) of tilmicosin significantly inhibited cell growth. When initial tilmicosin concentration increased from 0 to 50mgL-1, fractal dimension of microalgal cells monotonically increased from 1.36 to 1.62 and cell size monotonically decreased from 4.86 to 3.75µm. In parallel, malondialdehyde content, which represented the degree of cellular oxidative damage, monotonically increased from 1.92×10-7 to 7.07×10-7 nmol cell-1. Superoxide dismutase activity that represented cellular antioxidant capacity first increased from 2.59×10-4 to the peak of 6.60×10-4U cell-1, then gradually decreased to 2.39×10-4U cell-1. The maximum tilmicosin removal efficiency of 99.8% by Chlorella PY-ZU1 was obtained at the initial tilmicosin concentration of 50mgL-1.

Developing a water-circulating column photobioreactor for microalgal growth with low energy consumption.

A water-circulating column photobioreactor (WCC-PBR) was developed to decrease bubble generation time and mixing time for growing microalgal biomass at low energy consumption. Bubble generation time was decreased by 60.4% and mixing time was decreased by 41.5% owing to an enhanced solution velocity with a water pump. Bubble residence time was decreased by 31.1% and mass transfer coefficient was decreased by 0.4% owing to a reduced distance between air aerator and solution surface. Microalgal growth rate was decreased by 12.7% from 128.9mg/Lday in an air-lifting column photobioreactor (ALC-PBR) to 112.6mg/Lday in a WCC-PBR because of the decrease in residence time of bubbles and an additional shear of cells in a water pump. However, total energy consumption of a WCC-PBR with an air compressor and a water pump was lower by 21.1% than that of an ALC-PBR with only an air compressor.

Decrease in light/dark cycle of microalgal cells with computational fluid dynamics simulation to improve microalgal growth in a raceway pond.

In this study, computational fluid dynamics (CFD) was used to systemically analyze the movement of algae in a vortex flow field produced by up-down chute baffles. The average cell light/dark (L/D) cycle period, vertical fluid velocity, fraction of time the algae was resides in light zone and the L/D cycle period were investigated under different paddlewheel speeds and microalgal concentrations. Results showed that the L/D cycle period decreased but the vertical fluid velocity increased when the up-down chute baffles were used. The L/D cycle period decreased by 24% (from 5.1s to 3.9s), and vertical fluid velocity increased by 75% when up-down chute baffles were used with paddlewheel speed of 30r/min. The probability of L/D cycle period of 3s increased by 52% from 0.29 to 0.44 with the up-down chute baffles. This led to approximately 22% increase in biomass yield without changing the paddlewheel speed.

Gradient domestication of Haematococcus pluvialis mutant with 15% CO2 to promote biomass growth and astaxanthin yield.

In order to increase biomass yield and reduce culture cost of Haematococcus pluvialis with flue gas from coal-fired power plants, a screened mutant by nuclear irradiation was gradually domesticated with 15% CO2 to promote biomass dry weight and astaxanthin yield. The biomass yield of mutant after 10 generations of 15% CO2 domestication increased to 1.3 times as that with air. With the optimization of nitrogen and phosphorus concentration, the biomass dry weight was further increased by 62%. The astaxanthin yield induced with 15% CO2 and high light of 135 µmol photons m(-2) s(-1) increased to 87.4mg/L, which was 6 times higher than that induced with high light in air.

Improving microalgal growth with small bubbles in a raceway pond with swing gas aerators.

A novel swing gas aerator was developed to generate small bubbles for improving the mass transfer coefficient and microalgal growth rate in a raceway pond. A high-speed photography system (HSP) was used to measure the bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure the mass transfer coefficient and mixing time. Bubble generation time and diameter decreased by 21% and 9%, respectively, when rubber gas aerators were swung in the microalgae solution. When water pump power and gas aeration rate increased in a raceway pond with swing gas aerators and oscillating baffles (SGAOB), bubble generation time and diameter decreased but solution velocity and mass transfer coefficient increased. The mass transfer coefficient increased by 25% and the solution velocity increased by 11% when SGAOB was used, and the microalgal biomass yield increased by 18%.

Improving pollutants removal by microalgae Chlorella PY-ZU1 with 15% CO2 from undiluted anaerobic digestion effluent of food wastes with ozonation pretreatment.

In order to purify various pollutants (3108mg COD/L, 2120mg NH3-N/L) in the undiluted anaerobic digestion effluent of food wastes (UADEFW), ozonation pretreatment was employed to improve pollutants removal by microalgae mutant Chlorella PY-ZU1 with 15% CO2. Ozonation pretreatment broke CC bonds and benzene rings of refractory organics such as unsaturated fatty acids and phenols in UADEFW and degraded them into low-molecular-weight organics such as methanoic acid and methanal, but excessive ozone induced the accumulation of toxic by-products. The microalgal growth rate and biomass yield markedly increased to the peaks of 456mg/L/d and 4.3g/L, respectively, when the UADEFW was pretreated with 2mg-O3/mg-C of ozone. The removal efficiencies of NH3-N, TP and COD reached 99%, 99% and 68%, respectively. The lipid and carbohydrate contents of microalgal biomass increased because of the relative lack of nitrogen when microalgae was cultured with 15% CO2 to purify the UADEFW with ozonation pretreatment.

Optimizing gas transfer to improve growth rate of Haematococcus pluvialis in a raceway pond with chute and oscillating baffles.

Up-down chute and oscillating (UCO) baffles were used to generate vortex and oscillating flow field to improve growth rate of Haematococcus pluvialis in a raceway pond. Effects of gas flow rate, solution velocity, and solution depth on solution mass transfer coefficient and mixing time were evaluated using online pH and dissolved oxygen probes. Mass transfer coefficient increased by 1.3 times and mixing time decreased by 33% when UCO baffles were used in the H. pluvialis solution, resulting in an 18% increase in biomass yield with 2% CO2. The H. pluvialis biomass yield further increased to 1.5g/L, and astaxanthin composition accumulated to 29.7mg/L under relatively higher light intensity and salinity.

Enhanced energy recovery from cassava ethanol wastewater through sequential dark hydrogen, photo hydrogen and methane fermentation combined with ammonium removal.

Cassava ethanol wastewater (CEW) was subjected to sequential dark H2, photo H2 and CH4 fermentation to maximize H2 production and energy yield. A relatively low H2 yield of 23.6mL/g soluble chemical oxygen demand (CODs) was obtained in dark fermentation. To eliminate the inhibition of excessive NH4(+) on sequential photo fermentation, zeolite was used to remove NH4(+) in residual dark solution (86.5% removal efficiency). The treated solution from 5gCODs/L of CEW achieved the highest photo H2 yield of 369.7mL/gCODs, while the solution from 20gCODs/L gave the lowest yield of 259.6mL/gCODs. This can be explained that photo H2 yield was correlated to soluble metabolic products (SMPs) yield in dark fermentation, and specific SMPs yield decreased from 38.0 to 18.1mM/g CODs. The total energy yield significantly increased to 8.39kJ/gCODs by combining methanogenesis with a CH4 yield of 117.9mL/gCODs.

Improving microalgal growth with reduced diameters of aeration bubbles and enhanced mass transfer of solution in an oscillating flow field.

A novel oscillating gas aerator combined with an oscillating baffle was proposed to generate smaller aeration bubbles and enhance solution mass transfer, which can improve microalgal growth in a raceway pond. A high-speed photography system (HSP) was used to measure bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure mass-transfer coefficient and mixing time. Bubble diameter and generation time decreased with decreased aeration gas rate, decreased orifice diameter, and increased water velocity in the oscillating gas aerator. The optimized oscillating gas aerator decreased bubble diameter and generation time by 25% and 58%, respectively, compared with a horizontal tubular gas aerator. Using an oscillating gas aerator and an oscillating baffle in a raceway pond increased the solution mass-transfer coefficient by 15% and decreased mixing time by 32%; consequently, microalgal biomass yield increased by 19%.

Enhanced solution velocity between dark and light areas with horizontal tubes and triangular prism baffles to improve microalgal growth in a flat-panel photo-bioreactor.

Novel horizontal tubes and triangular prism (HTTP) baffles that generate flow vortices were developed to increase solution velocity between dark and light areas and thus improve microalgal growth in a flat-panel photo-bioreactor. Solution velocity, mass-transfer coefficient, and mixing time were measured with a particle-imaging velocimeter, dissolved oxygen probes, and pH probes. The solution mass-transfer coefficient increased by 30% and mixing time decreased by 21% when the HTTP baffles were used. The solution velocity between dark and light areas increased from ∼0.9cm/s to ∼3.5cm/s, resulting in a decreased dark-light cycle period to one-fourth. This enhanced flashing light effect with the HTTP baffles dramatically increased microalgae biomass yield by 70% in the flat-panel photo-bioreactor.

Enhancing the growth rate and astaxanthin yield of Haematococcus pluvialis by nuclear irradiation and high concentration of carbon dioxide stress.

Unicellular green microalgae Haematococcus pluvialis was mutated with (60)Co-γ irradiation to promote growth rate and increase astaxanthin yield under high concentration of CO2 stress. The average specific growth rate of H. pluvialis mutated with 4000 Gy γ-ray irradiation was increased by 15% compared with the original strain with air aeration. The mutant grew best with 6% CO2 (the maximum specific growth rate was 0.60/d) when it was cultured with high concentrations of CO2 (2-10%). The peak biomass productivity (0.16 g/L/d) of the mutant cultured with 6% CO2 was 82% higher than that of the mutant with air. The astaxanthin yield and lipid content of the mutant induced with 6% CO2 and high light (108 µmol photons m(-2) s(-1)) increased to 46.0mg/L and 45.9%, which were 2.4 and 1.3 times higher than those of the wild-type strain, respectively.

Improving CO2 fixation with microalgae by bubble breakage in raceway ponds with up-down chute baffles.

The aeration gas was broken into smaller bubbles with enhanced local solution velocity to improve CO2 fixation with microalgae in raceway ponds with up-down chute baffles. A high-speed photography system and online precise pH probes were used to measure bubble generation and residence times, which were affected by paddlewheel speed, aerator orifice diameter, gas flow rate, and solution depth. Bubble generation time (from gas reaching aerator orifice surface to completely escaping from the aerator) decreased because of the enhanced local solution velocity, whereas bubble residence time increased because of the vortex flow field produced by up-down chute baffles. Bubble generation time decreased by 27% and bubble residence time increased by 27% when paddlewheel speed was 10r/min with an aeration gas rate of 0.03vvm. The decreased generation time and increased residence time of aeration bubbles promoted microalgae biomass yield by 29% in optimized flow fields in raceway ponds.

Microstructures and functional groups of Nannochloropsis sp. cells with arsenic adsorption and lipid accumulation.

The pore structures and surface morphological characteristics of Nannochloropsis sp. cells with arsenic adsorption were initially investigated by N2-adsorption analysis and scanning electronic microscopy. Functional groups of cells were analysed by Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy. Total surface area of microalgal cells increased from 0.54 m(2)/g to 1.80 m(2)/g upon arsenic adsorption. The external cell surface area increased. More wrinkles and measles-like granules formed on the surfaces as a result of arsenic toxicity. Arsenic ions blocked cell pores and decreased the average pore diameter and total pore volume. Ether cross-linked structures in the algaenan layer of cell walls were disrupted as the percentage of C-O functional groups decreased. These functional groups underwent complexation reactions with arsenic ions. Accumulation of polyunsaturated fatty acids decreased because of oxidative stresses induced by arsenic. The increase in generation of short-chain saturated fatty acids was favourable for the production of quality biodiesel.

Improving growth rate of microalgae in a 1191m(2) raceway pond to fix CO2 from flue gas in a coal-fired power plant.

CO2 fixation between microalgal biomass and culture solution and the weight ratio of biomass consumption at nighttime to biomass growth at daytime were compared in an open raceway pond aerated with flue gas from a coal-fired power plant. Average daytime sunlight intensity and solution temperature were optimized to improve microalgal growth rate and to enhance the efficiency of CO2 fixation. When the average daytime solution temperature increased from 12 to 26°C, the rate of biomass consumption due to microalgal respiration at nighttime increased from 6.0 to 7.9g/m(2)/d, which was approximately 25% of the biomass growth rate at daytime. Furthermore, when the average daytime sunlight intensity increased from 39,900 to 88,300lux, CO2 fixation rate in the microalgal biomass increased from 18.4 to 40.7g/m(2)/d, which was approximately 1/3 of CO2 removal rate from flue gas by the microalgal culture system.

Enhanced flashing light effect with up-down chute baffles to improve microalgal growth in a raceway pond.

Novel up-down chute baffles that sequentially generate clockwise and anticlockwise liquid vortexes were developed to increase vertical liquid velocity between the bottom dark area and the top light area in a raceway pond. The vertical liquid velocity, mixing time, and mass transfer coefficient were measured as functions of paddlewheel speed and air aeration rate by using a particle imaging velocimeter, pH probes, and dissolved oxygen probes. The up-down chute baffles decreased the liquid mixing time and increased the mass transfer coefficient by 41% and 25%, respectively. Besides, the vertical liquid velocity increased from ∼0.5cm/s to ∼6.1cm/s. As a result, the dark-light cycle period was reduced to 1/12. This enhanced flashing light effect with up-down chute baffles increased biomass yield by 32.6% in the same raceway pond.