Experimental study on microalgae cultivation in novel photobioreactor of concentric double tubes with aeration pores along tube length direction

Microalgae have been identified as a superior feedstock for biodiesel production and varied tubular photobioreactors are developed for high efficient and scale-up microalgae cultivation. This article presented a novel concentric double tubes using aeration through radial pores along the length direction of inner tube. Experiments on microalgae cultivation were carried out in the novel photobioreactor, and two control groups including concentric double tubes with axial aeration at both ends and common tubular. The biomass productivity of novel photobioreactor increased by 43.6% and 107.4%, respectively, compared with concentric double tubes with axial aeration at both ends and common tubular without aeration. The values of pH shifted from 7.5 to 9.0 for novel photobioreactor, but 7.5 to 8.8 for common tubular, and 7.5 to 9.6 for concentric double tubes with axial aeration. The dissolved oxygen concentration fluctuated between 6.0 and 7.0 mg·L^?1 for novel photobioreactor, but rose from 6.6 to 10.2 mg·L^?1 for the common tubular, and 6.9 to 8.1 mg·L^?1 for the concentric with axial aeration. Results show that the aeration style of novel photobioreactor can make efficient local mixing and maintain smaller range of pH and lower level of dissolved oxygen in case of higher biomass concentration. Moreover, compared with the two control groups, the novel concentric double tubes have advantages on the light/dark cycle frequency, which may be benefit for microalgae cultivation. The novel concentric double tubes presented in this work can give some inspiration for high efficiency microalgae cultivation.     

Effect of Light on Biodegradation of Estrone, 17β‐Estradiol,and 17α‐Ethinylestradiol in Stream Sediment

Biodegradation of [A‐ring ¹⁴C] Estrone (E1), 17β‐estradiol (E2), and 17α‐ethinylestradiol (EE2) to ¹⁴CO₂ was investigated under light and dark conditions in microcosms containing epilithon or sediment collected from Boulder Creek, Colorado. Mineralization of the estrogen A‐ring was observed in all sediment treatments, but not epilithon treatments. No difference in net mineralization between light and dark treatments was observed for ¹⁴C‐E2. Net mineralization of ¹⁴C‐E1 and ¹⁴C‐EE2 was enhanced in light treatments. Extents of ¹⁴CO₂ accumulation and rates of mineralization were significantly greater for E2 than E1 under dark conditions, but were comparable under light conditions. These results indicate substantial differences in the uptake and metabolism of E1 and E2 in the environment and suggest biorecalcitrance of E1 relative to E2 in light‐limited environments. The extent of ¹⁴CO₂ accumulation and rate of mineralization for EE2 in dark treatments were less than half of that observed for E2 and generally lower than for E1, consistent with previous reports of EE2 biorecalcitrance. However, ¹⁴CO₂ accumulation and rates of mineralization were comparable for EE2, E2, and E1 under light conditions. These results indicate photoactivation and/or phototransformation/photodegradation processes can substantially enhance heterotrophic biodegradation of estrogens in sunlit environments and may play an important role in estrogen transport and attenuation.     

Intensification of treatment processes for oily wastewater: Theoretical foundations for calculating the hydrodynamic characteristics of tube coalescers

We present the results of theoretical studies of the pressure fluid flow fundamental characteristics in tube coalescers used in the treatment processes for oily wastewater. It is shown that three different regions of flow (wall sublayer, transition sublayer, and flow kernel), having their own hydrodynamic characteristics, are formed in a cross section of the tube coalescer. In the viscous wall sublayer (of thickness δ_*), viscous frictional forces exceed inertial forces (Re_δ* < 1), and “creeping flow” is observed. This region borders on the transition sublayer (of thickness δ_** = δ_*), in which inertial forces exceed viscous frictional forces (Re_δ** > 1). For both laminar and turbulent flow, distribution laws of local velocities and velocity gradients along the pipe radius are obtained in each of the three regions. In the flow kernel, the linear distribution law of velocity gradients gives a square distribution law of velocities for both types of flow, but for the turbulent flow, the correction coefficients A = β and B = 2β ? 1 must be introduced.     

Microalgae‐based biodiesel production in open raceway ponds using coal thermal flue gas: A case of West Bengal,India

India is one of the most populous countries and is the third largest greenhouse gas–emitting nation. Energy security is a serious issue for India as it relies heavily on fossil fuel imports. Biodiesel production using microalgae as feedstock can address both of these issues. In this study, the technical feasibility of microalgae‐based biodiesel production is carried out for a coal thermal power plant (i.e., Budge Budge Thermal Station) in the state of West Bengal, India, using a generic methodology. An oleaginous microalgae species that is tolerant toward flue gas was identified (i.e., Nannochloropsis sp). A 75‐acre open raceway microalgae production plant was designed keeping the costs, energy demand, and CO₂ emissions low. The open raceway pond can use 38 tons of CO₂, produce 19 tons of algal biomass, and treat 9320 m³ of wastewater per acre annually.     

Limiting the impact of light pollution on human health, environment and stellar visibility

Light pollution is one of the most rapidly increasing types of environmental degradation. Its levels have been growing exponentially over the natural nocturnal lighting levels provided by starlight and moonlight. To limit this pollution several effective practices have been defined: the use of shielding on lighting fixture to prevent direct upward light, particularly at low angles above the horizon; no over lighting, i.e. avoid using higher lighting levels than strictly needed for the task, constraining illumination to the area where it is needed and the time it will be used. Nevertheless, even after the best control of the light distribution is reached and when the proper quantity of light is used, some upward light emission remains, due to reflections from the lit surfaces and atmospheric scatter. The environmental impact of this "residual light pollution", cannot be neglected and should be limited too. Here we propose a new way to limit the effects of this residual light pollution on wildlife, human health and stellar visibility. We performed analysis of the spectra of common types of lamps for external use, including the new LEDs. We evaluated their emissions relative to the spectral response functions of human eye photoreceptors, in the photopic, scotopic and the 'meltopic' melatonin suppressing bands. We found that the amount of pollution is strongly dependent on the spectral characteristics of the lamps, with the more environmentally friendly lamps being low pressure sodium, followed by high pressure sodium. Most polluting are the lamps with a strong blue emission, like Metal Halide and white LEDs. Migration from the now widely used sodium lamps to white lamps (MH and LEDs) would produce an increase of pollution in the scotopic and melatonin suppression bands of more than five times the present levels, supposing the same photopic installed flux. This increase will exacerbate known and possible unknown effects of light pollution on human health, environment and on visual perception of the Universe by humans. We present quantitative criteria to evaluate the lamps based on their spectral emissions and we suggest regulatory limits for future lighting.     

Light-limited population dynamics of phytoplankton: modeling light and depth effects

Light has received very less attention as a selective factor, probably because the changing vertical light gradient makes light a rather complex factor when compared with the nutrient competition. In our study we modified an analytically tractable model based upon the Beer–Lambert law. The study aimed to predict the outcome of phytoplankton competition for light, on the basis of field measurements. When we considered competition theory, Fragilaria was found to be more competitive than other genera. The overall result shows that the trends flow in the following manner; Fragilaria > Gomphonema > Diatoma > Amphora > Achnanthes.     

CHANNEL MORPHOLOGY EVOLUTION AND OVERBANK FLOW IN THE GEORGIA PIEDMONT1

ABSTRACT: Historic changes in stream channel morphology were investigated in the Georgia Piedmont to better understand the hydrologic processes and functioning of the region's riverine systems. USGS gaging station data and channel geomorphology data were collected from thirty study sites in the Upper Oconee River Basin for flood frequency analysis. Historic and modern (i.e., present-day) channel capacity discharge (i.e., overbank flow) was calculated using Manning's equation and historic channel cross-section records. The recurrence interval for overbank flow was estimated for each site from flood frequency data. Results indicate that channel expansion has occurred throughout the basin, especially in upper reaches. Recurrence intervals for modern overbank events were variable and generally high ranging from < 2 to > 500 years for first to third order streams. They were less variable and lower for fourth and fifth order streams, ranging from < 2 to 3 years. Potential depositional thresholds were identified that exemplify the complex response of sediment distribution patterns throughout the basin. Results indicate overbank flows occur less frequently now than they once did due to historic accelerated sedimentation and subsequent channel expansion. One application of these findings is that these basin processes are likely applicable across the region and may impact the hydrologic functioning of associated Piedmont riverine wetlands that depend on flooding regimes.     

Evaluating the impact of fractures on the performance of the In Salah CO2 storage site

The In Salah Gas Joint Venture CO₂ storage project has been in operation in Algeria since 2004 and is currently the world's largest onshore CO₂ storage project. CO₂ is injected into the saline aquifer of a gas reservoir several kilometres away from the gas producers. Current focus in the project is on implementing a comprehensive monitoring strategy and modelling the injection behaviour in order to ensure and verify safe long-term storage. A key part of this effort is the understanding of the processes involved in CO₂ migration within relatively low-permeability sandstones and shales influenced by fractures and faults. We summarise our current understanding of the fault and fracture pattern at this site and show preliminary forecasts of the system performance using discrete fracture models and fluid flow simulations. Despite evidence of fractures at the reservoir/aquifer level, the thick mudstone caprock sequence is expected to provide an effective flow and mechanical seal for the storage system; however, quantification of the effects of fracture flow is essential to the site verification.     

Demonstration of a high throughput on-board hydrogen generation reactor system using aluminum coil as fuel for a vehicle

A novel on-board hydrogen generation concept using Al coil with NaOH was investigated. The reaction rate was successfully controlled by introducing a pumping system for the NaOH solution. The time for the flow to develop fully was mainly dependent on the solution temperature, and the fastest start time recorded was 60 sec at a solution temperature of 70°C. The maximum H₂ generation rate was 200 L min^–1 with a prototype design of the on-board hydrogen generation system 1/8 times the size of a full-size reactor. The H₂ generation process coupled with the solution pumping system was simulated with three-dimensional fluid dynamic software, and the calculated H₂ flow and temperature rise of the system were validated with experimental data.     

Comparative performance study of different configurations of organic Rankine cycle using low-grade waste heat for power generation

This paper aims at analyzing the feasibility of a waste heat recovery power generation plant based on parametric optimization and performance analysis using different organic Rankine cycle configurations and heat source temperature conditions with working fluid R-12, R-123, R-134a, and R-717. A parametric optimization of turbine inlet temperature(TIT) was performed to obtain the irreversibility rate, system efficiency, availability ratio, turbine work output, system mass flow rate, second-law efficiency, and turbine outlet quality, along the saturated vapor line and also on superheating at an inlet pressure of 2.50 MP in basic as well as regenerative organic Rankine cycle. The calculated results reveal that selection of a basic organic Rankine cycle using R-123 as working fluid gives the maximum system efficiency, turbine work output, second-law efficiency, availability ratio with minimum system irreversibility rate and system mass flow rate up to a TIT of 150°C and appears to be a choice system for generation of power by utilizing the flue gas waste heat of thermal power plants and above 150°C the regenerative superheat organic Rankine cycle configuration using R 123 as working fluid gives the same results.     

A well to wire LCA model development and sensitivity analysis for carbon footprint of combined cycle power plants in Iranian electricity network

The present research introduces a well to wire pseudo comprehensive carbon footprint model for combined cycle power plants. The mentioned model integrates land use change model, operational model and transmission and distribution model into one comprehensive model. The parameters which their effects are considered in the integrated model are: fuel type, fuel transmission type, emission for fuel extraction and processing, own consumption of the plant, degradation, site ambient condition, transmission and distribution losses. For quantifying the effectiveness of each parameter, sensitivity analyses based on different life cycle scenarios are performed. The result shows that the effect of land use change is negligible. The carbon footprint of electrical energy produced in combined cycle plant until it is delivered to the end users varies from 321 to 522 g CO₂ eq/kWh.     

Investigation of geothermal energy utilization for thermal regulation of aquaculture raceway

ABSTRACT

Aquaculture raceway temperature has a direct impact on the aquatic specie being reared. In regions that undergo significant seasonal temperature variations, the thermal management of the raceway temperature becomes a challenge, directly impacting the production yield. This study investigates a novel approach to regulate the raceway temperature in a sustainable way by utilizing geothermal energy. A numerical energy model was developed to simulate heat transfer in a geothermal system encompassing both the individual borehole heat exchangers and their thermal interactions. Simulations were conducted for different configurations of the geothermal system over a complete seasonal cycle. Results show that flow rate, number of boreholes and the borehole spacing influence the temperature of the fluid at the raceway inlet. An increase in the number of boreholes provided better thermal regulation but an increase in the flow rate through the boreholes provided less thermal regulation. A borehole spacing of 6 m was found to be appropriate to reduce thermal interference. It was also observed that an increase in the fraction of the fluid passed through the geothermal system enhances the overall thermal regulation, with higher thermal regulation at lower flow rates. Results show that when 100% of the fluid passed through a 64 boreholes geothermal system, the average regulated raceway inlet temperature was 23% higher in winter months and 16% lower in summer months at the flow rate of 21.5 L/s compared to than at 43 L/s.     

The determination and matching analysis of pinch point temperature difference in evaporator and condenser of organic rankine cycle for mixed working fluid

Exergo-economic analysis of the pinch point temperature difference (PPTD) in both evaporator and condenser of sub-critical organic Rankine cycle system (ORCs) are performed based on the first and second laws of thermodynamics. Taking mixture R13I1/R601a as a working fluid and the annual total cost per net output power Z as exergo-economic performance evaluation criterion, the effects of PPTD in evaporator ΔT_e, and the PPTD ratio of condenser to evaporator y, on the exergo-economic performance of ORCs are analyzed. Moreover, how some other parameters influence the optimal PPTD in evaporator ΔT_e,opt and the optimal PPTD ratio of condenser to evaporator y_opt are also discussed. It has been found that the exergo-economic performance of ORCs is remarkably influenced by ΔT_e and y, and there exists ΔT_e,opt and y_opt. In addition, ΔT_e,opt and y_opt are affected by heat transfer coefficient ratio of condenser to evaporator ß, the temperature of working fluid at dew point in condenser T_1a, and composition of R13I1/R601a: larger ß and T_1a lead to lower ΔT_e,opt and y_opt; by contraries, larger mass fraction of R13I1 makes ΔT_e,opt and y_opt increase, and y_opt increases linearly. The effects of the temperature of working fluid at bubble point in evaporator T_3a, mass flow rate of exhaust flue gas m_g, and inlet temperature of exhaust flue gas T_gi on ΔT_e,opt and y_opt are very slight. For comparison, three additional working fluids, namely R601a, R245fa, and 0.32R245fa/0.68R601a, are also taken into account.     

Petrophysical analysis to investigate the effects of carbon dioxide storage in a subsurface saline aquifer at Ketzin, Germany (CO2SINK)

To test the injection behaviour of CO₂ into brine-saturated rock and to evaluate the dependence of geophysical properties on CO₂ injection, flow and exposure experiments with brine and CO₂ were performed on sandstone samples of the Stuttgart Formation representing potential reservoir rocks for CO₂ storage. The sandstone samples studied are generally fine-grained with porosities between 17 and 32% and permeabilities between 1 and 100 mD.Additional batch experiments were performed to predict the long-term behaviour of geological CO₂ storage. Reservoir rock samples were exposed over a period of several months to CO₂-saturated reservoir fluid in high-pressure vessels under in situ temperature and pressure conditions. Petrophysical parameters, porosity and the pore radius distribution were investigated before and after the experiments by NMR (Nuclear Magnetic Resonance) relaxation and mercury injection. Most of the NMR measurements of the tested samples showed a slight increase of porosity and a higher proportion of large pores.     

Treatment of Dichloromethane Using Gliding Arc Plasma

Decomposition of dichloromethane (CH₂Cl₂) using a gliding plasma was examined and reported in this paper. The effects of initial concentrations of CH₂Cl₂, total gas flow rates, and input frequency have been studied to evaluate the performance of gliding arc on CH₂Cl₂ decomposition. Using atmospheric pressure air as the carrier gas, experimental results indicate that the maximum conversion of CH₂Cl₂ was 95.1% at a total gas flow rate of 180 L/hr containing 1% by volume of CH₂Cl₂. The reaction occurred at an exothermic condition and gaseous products are dominated by CO, CHCl₃, and Cl₂. CO₂ and CCl₄ are also detected in the product stream in small amounts. The conversion of CH₂Cl₂ increases with the increasing applied voltage and decreasing total gas flow rate.     

Study of the performance of a coolant mixed with an Al2O3/SiC nanomaterial in an engine radiator

One of the important components of a car to control the temperature of a car's engine is the radiator. To increase the heat absorption capacity of the coolant/fluid used in the radiator with minimum pumping power, innovative fluids called nanofluids have become the main area of research these days. Therefore, with the development of new technologies in the field of “nano-materials” and “nano-fluids,” the physical and chemical properties of coolant/fluid can be improved which in turn improves the radiator and engine efficiency, and reduces radiator weight and size. In this article, the heat transfer by forced convection in nanofluids based on Al₂O₃ and SiC was studied experimentally and compared to that of base fluid in an automotive radiator. The nanofluid is mixed with ethylene glycol and the fluid is prepared by the sonication method. The nanofluids were prepared by varying the nanomaterials and the amounts of nanomaterials in the base fluid and their heat transfer performance in the radiator was analyzed using ANSYS FLUENT software. Approximately 15% and 12% increase in radiator efficiency by using Al₂O₃ mixed nanofluid and SiC mixed nanofluid, respectively.     

A future for the forest of dean

Summary This article outlines the historical background of the Forest of Dean in Gloucestershire and the Acts of Parliament which have affected its landscape character. Problems relating to the present situation are discussed. These include rights of access, common rights, sales of public land, intrusion of industry, open cast mining and tourism. The suggestion is put forward that there should be a new Act of Parliament establishing a Dean Forest Authority which would be an autonomous estate management body with an executive committee drawn from the many interests in the district. The Forestry Commission, which is at present responsible for management, with its main concern that of commercial tree growing, is not considered to be sufficiently sympathetic to local needs. The author originally intended reading for a Forestry degree at Oxford, but eventually took a degree in Botany at that University (1957). For some time he was Biology teacher at King Edward VI's School, Norwich, and Head of Science at the Blyth School, Norwich. Since establishing the Centre for Environmental Studies for the Gloucestershire Education Authority in the Forest of Dean in 1969 he has become closely involved with a number of conservation organisations in Gloucestershire. He was for a time chairman of the Dean branch of the Council for the Protection of Rural England and the North Dean Reserves Committee of the Gloucestershire Trust for Nature Conservation. Besides writing the occasional paper on field studies and local history he writes a ‘Conservation Piece’ monthly for the local papers. He has been an outspoken critic on a number of local issues on radio, television and in local inquiries.     

Streamflow,Sediment Transport,and Geomorphic Change during the 2011 Flood on the Missouri River Near Bismarck–Mandan,ND

Geomorphic change from extreme events in large managed rivers has implications for river management. A steady‐state, quasi‐three‐dimensional hydrodynamic model was applied to a 29‐km reach of the Missouri River using 2011 flood data. Model results for an extreme flow (500‐year recurrence interval [RI]) and an elevated managed flow (75‐year RI) were used to assess sediment mobility through examination of the spatial distribution of boundary or bed shear stress (τ_b) and longitudinal patterns of average τ_b, velocity, and kurtosis of τ_b. Kurtosis of τ_b was used as an indicator of planform channel complexity and can be applied to other river systems. From differences in longitudinal patterns of sediment mobility for the two flows we can infer: (1) under extreme flow, the channel behaves as a single‐thread channel controlled primarily by flow, which enhances the meander pattern; (2) under elevated managed flows, the channel behaves as multithread channel controlled by the interaction of flow with bed and channel topography, resulting in a more complex channel; and (3) for both flows, the model reach lacks a consistent pattern of deposition or erosion, which indicates migration of areas of erosion and deposition within the reach. Despite caveats and limitations, the analysis provides useful information about geomorphic change under extreme flow and potential implications for river management. Although a 500‐year RI is rare, extreme hydrologic events such as this are predicted to increase in frequency.     

Thermo- and fluid-dynamical modelling of two-phase multi-component carbon dioxide mixtures

A method for calculating the transport and depressurization of a two-phase multi-component CO₂ mixture is presented. The thermodynamical and transport properties for a CO₂–CH₄ mixture are calculated using the Soave–Redlich–Kwong equation of state (SRK). The fluid flow is described by a drift-flux model, which is solved using the multi-stage (MUSTA) centred scheme. Numerical results are shown, illustrating the effect of mixture composition and the feasibility of the approach.     

CONFIDENCE INTERVALS FOR FLOOD EVENTS UNDER A PEARSON 3 OR LOG PEARSON 3 DISTRIBUTION1

ABSTRACT: The Pearson type 3 (P3) and log Pearson type 3 (LP3) distributions are very frequently used in flood frequency analysis. Existing methods for constructing confidence intervals for quantiles (X_p) of these two distributions are very crude. Most of these methods are based on the idea of adjusting confidence intervals for quantiles Y_p of the normal distribution to obtain approximate confidence inervals for quantiles X_p of the P3/LP3 distribution. Since there is no theoretical reason why this “base” distribution, Y, should be taken to be normal, we search in the present study for the best possible base distribution for producing confidence intervals for P3/LP3 quantiles. We consider a group of base distributions such as the normal, log normal, Weibull, Gumbel, and exponential. We first assume that the skew coefficient, γ of X, to be known, and develop a method for adjusting confidence intervals for Y_p to produce approximate confidence intervals for X_p. We then compare this method (Method A) with another method (Method B) introduced by Stedinger. Simulation shows that the performance of each of these two methods depends on the base distribution Y that is being used, but as a whole, the normal distribution appears to be the best-fit distribution for producing confidence intervals for P3/LP3 quantiles when γ is assumed to be known. We then extend our method (Method A) to the more important case of unknown coefficient of skewness. It is shown that by taking Y to be Weibull, fairly accurate confidence intervals for P3/LP3 quantiles can be obtained for quite a wide range of sample sizes and coefficients of skewness commonly found in hydrology. The case of the P3 distribution with negative skewness needs further research.