Algal Biomass Concentration Research Articles

Research on Biological Materials with Uranium Biosorption by Microalgae: A Review

With the development of nuclear science, uranium-contained wastewater was heavily generated. If not properly handled, it is bound to bring environmental and human health hazards. Conventional uranium-contained wastewater treatment technologies are limited in certain aspects, such as high reagent and energy consumption, secondary pollution and so on. The microalgae-based biosorption technique for treating uranium-contained wastewater is an economical, simple, effective and feasible approach. This paper summarized the basic mechanism of the technology, and discussed the effects of different pH, algal cell biomass concentration, initial uranium ion concentration and the growth state of algal cells on the biological treatment process of uranium-contained wastewater. Finally, the study explored the future prospects of the technology.

Rapid algal culture diagnostics for open ponds using multispectral image analysis

This article presents a multispectral image analysis approach for probing the spectral backscattered irradiance from algal cultures. It was demonstrated how this spectral information can be used to measure algal biomass concentration, detect invasive species, and monitor culture health in real time. To accomplish this, a conventional RGB camera was used as a three band photodetector for imaging cultures of the green alga Chlorella sp. and the cyanobacterium Anabaena variabilis. A novel floating reference platform was placed in the culture, which enhanced the sensitivity of image color intensity to biomass concentration. Correlations were generated between the RGB color vector of culture images and the biomass concentrations for monocultures of each strain. These correlations predicted the biomass concentrations of independently prepared cultures with average errors of 22 and 14%, respectively. Moreover, the difference in spectral signatures between the two strains was exploited to detect the invasion of Chlorella sp. cultures by A. variabilis. Invasion was successfully detected for A. variabilis to Chlorella sp. mass ratios as small as 0.08. Finally, a method was presented for using multispectral imaging to detect thermal stress in A. variabilis. These methods can be extended to field applications to provide delay free process control feedback for efficient operation of large scale algae cultivation systems.

A growth inhibitory model with SOx influenced effective growth rate for estimation of algal biomass concentration under flue gas atmosphere

A theoretical model for the prediction of biomass concentration under rice husk flue gas emission has been developed. The growth inhibitory model (GIM) considers the CO2 mass transfer rate, the critical SOx concentration and its role in pH-based inter-conversion of bicarbonate. The calibration and subsequent validation of the growth profile of Nannochloropsis limnetica at 2% and 10% (v/v) CO2 showed that the predicted values were consistent with the measured values, with r(2) being 0.96 and 0.98, respectively, and p<0.001 in both cases. The constants used in the GIM for the prediction of biomass have been justified using sensitivity analysis. GIM applicability was defined as ±30% of the calibrated flow rate (3.0 L min(-1)). This growth model can be applied to predict algal growth in photo-bioreactors treated with flue gas in the generation of biomass feed stock for biofuel production.

Extra- and intra-cellular accumulation of platinum group elements by the marine microalga, Chlorella stigmatophora

To better understand the marine biogeochemistry of the platinum group elements (PGE), Rh(III), Pd(II) and Pt(IV) were added in combination and at ppb concentrations to cultures of the marine microalga, Chlorella stigmatophora, maintained in sea water at 15 °C and under 60 μmol m−2 s−1 PAR. The accumulation of PGE was established in short-term (24-h) exposures, and under varying conditions of algal biomass and PGE concentration, and in a longer-term exposure (156-h) by ICP-MS analysis of sea water and nitric acid digests and EDTA washes of the alga. In short-term exposures, and under all conditions, the extent of accumulation by C. stigmatophora was in the order: Rh > Pd >> Pt; and Pd was internalised (or resistant to EDTA extraction) to a considerably greater extent than Rh and Pt. Accumulation isotherms were quasi-linear up to added PGE concentrations of 30 μg L−1 and all metals displayed a significant reduction in accumulation on a weight-normalised basis with increasing density (biomass) of C. stigmatophora, an effect attributed to the production of exudates able to stabilise metals in sea water through complexation. In the longer-term exposure, kinetic constraints on the reactivities of Rh and, in particular, Pt, resulted in final degrees of accumulation and internalisation by C. stigmatophora that were greatest for Rh and similar between Pd and Pt. Among the PGE, therefore, Rh is predicted to participate in biological removal and transport processes in the marine environment to the greatest extent while decoupling in the biogeochemistries of Pd and Pt is predicted in shorter-term or more transient processes.

Development of a photoelectrochemical sensor for monitoring algal biomass (Chlorella vulgaris)

Herein, we present a novel photoelectrochemical sensor system for the rapid enumeration of algal biomass. The photosynthesis-based reducing action of algal cells on the electrochemical mediator 2-hydroxyl-1,4-naphthoquinone (HNQ) was used as the basis of an amperometric sensor system. By using a simple LED (Light-Emitting Diode) installed three-electrode cell, the mediator that was reduced by algal metabolic activity was reoxidized at a platinum-working electrode and held at a positive potential. In the presence of CO2 as an electron donor, and LED illumination as an energy source for the algal cells, the reoxidation current and its rate of increase were found to depend on the concentration of algal biomass. Regression analyses plotting the initial rate of current (μAmin−1) against algal biomass concentrations (gL−1) produced a reasonable correlation coefficient (r2=0.9938). The sensor system exhibited a high sensitivity to algal biomass at a concentration as low as 0.065gL−1and a rapid response time, which is promising for further applications of the sensor system in algal-related industries.

Simulating pH effects in an algal-growth hydrodynamics model(1).

Models and numerical simulations are relatively inexpensive tools that can be used to enhance economic competitiveness through operation and system optimization to minimize energy and resource consumption, while maximizing algal oil yield. This work uses modified versions of the U.S. Environmental Protection Agency's Environmental Fluid Dynamics Code (EFDC) in conjunction with the U.S. Army Corp of Engineers' water-quality code (CE-QUAL) to simulate flow hydrodynamics coupled to algal growth kinetics. The model allows the flexibility of manipulating a host of variables associated with algal growth such as temperature, light intensity, and nutrient availability. pH of the medium is a newly added operational parameter governing algal growth that affects algal photosynthesis, differential availability of inorganic forms of carbon, enzyme activity in algae cell walls, and oil production rates. A single-layer algal-growth/hydrodynamic model without pH limitation was verified by comparing solution curves of algal biomass and phosphorus concentrations to an analytical solution. Media pH, now included in the model as a growth-limiting factor, can be entered as a measured value or calculated based on CO2 concentrations. Upon adding the ability to limit growth due to pH, physically reasonable results have been obtained from the model both with and without pH limitation. When the model was used to simulate algal growth from a pond experiment in the greenhouse, a least-squares fitting technique yielded a maximum algal production (subsequently modulated by limitation factors) of 1.05d(-1) . Overall, the measured and simulated biomass concentrations in the greenhouse pond were in close agreement.

High-density fed-batch culture of a thermotolerant microalga Chlorella sorokiniana for biofuel production

Culturing microalgae heterotrophically for producing lipid-based biofuels such as biodiesel and renewable hydrocarbons has attracted increasing attention due to the advantages of fast growth and high lipid yield under this growth mode without being subjected to light limitation. High cell density in the culture broth is desirable for reducing downstream processing costs. Oleaginous microalga Chlorella sorokiniana was investigated for high cell density culture with glucose as the carbon source. Best growth performance was obtained first with batch culture at pH 7.0 when ammonium was the nitrogen source. Then, two-stage fed-batch fermentation was conducted under the optimal conditions. The algal biomass grew linearly in the first stage with a productivity of 24.2gL−1d−1, and the lipid content increased from 14.5% to 38.7% in the second stage. This fermentation strategy resulted in algal biomass and lipid concentrations of 103.8gL−1 and 40.2gL−1 respectively. Analysis of lipid and fatty acid profiles showed C. sorokiniana accumulated a large amount of neutral lipids (92.9% of total lipids), triacylglycerols (82.8% of neutral lipids), and high contents of palmitic, oleic and linoleic acids, which are ideal form of lipid for making biodiesel. These results suggest that heterotrophic culture of C. sorokiniana holds great potential for lipid-based biofuel production.

Primary production, food web structure, and fish yields in constructed and natural wetlands in the floodplain of an African river

In the Ouémé River, Africa, whedo (artificial pond) aquaculture on the floodplain is an important method of fishery production. We surveyed fishes in whedos and adjacent main-channel and floodplain habitats during the receding-water period (December 2010 – January 2011) and analyzed carbon (δ13C) and nitrogen (δ15N) stable isotope ratios of fish and primary producer tissue samples to investigate food web structure. We also measured instream respiration, net primary production, algal biomass (chlorophyll a), and nutrient concentrations in the habitats. Floodplain habitats were more nutrient-rich than the river channel, and whedos were net heterotrophic (net primary production &lt; 0). Phytomicrobenthos and C3 macrophytes accounted for a large fraction of fish biomass in whedos and the natural floodplain depression, while the river channel was mainly supported by seston and C3 macrophytes. Whedo food webs were dominated by piscivorous fishes and had fewer trophic transfers compared with the food web of the river channel. Our results suggest that control of aquatic macrophyte growth in whedos may yield greater algal production and consumer biomass, including harvestable fish stocks.

Degradation of an azo dye using the green macroalga Enteromorpha sp.

This paper documents the biological treatment of C.I. Basic Red 46 (BR46) solution using the green macroalga Enteromorpha sp. A central composite design (CCD) was used for optimisation of the biological decolourisation process. The investigated variables were reaction time, temperature, algal biomass and initial dye concentration. Predicted values were found to be in good agreement with experimental values (R 2=0.988, Adj R 2=0.978), which indicated the suitability of the CCD model for optimising this process. The predicted results from CCD indicated that 83.45% biological dye removal was achieved under optimum conditions with a reaction time of 5 h, a temperature of 25 °C, alga biomass of 2 g and initial dye concentration of 15 mg/L. Biological degradation of BR46 was revealed on the basis of repeated-batch operations and gas chromatography-mass spectrometry analysis. Seven compounds were successfully identified as the biological degradation compounds formed in this process.

Flocculation Optimization of Microalga Nannochloropsis oculata

The objective of this work was to understand and optimize the flocculation of a marine alga Nannochloropsis oculata with two cationic salts, aluminum sulfate (AS), and ferric chloride (FC). Based on single-factor and response-surface-methodology experiments, second-order polynomial models were developed to examine the effect of initial algal biomass concentration (IABC), pH, and flocculant dose (FD) on final solid concentration of algae (SCA). The experimental and modeling results showed that SCA favored low pH, which however was undesirable to biomass recovery rate. There existed a positive stoichiometric relationship between FD and IABC; higher IABC required higher FD, and vice versa, for higher SCA. Optimum flocculation conditions were predicted at IABC of 1.7 g/l, pH8.3, and FD of 383.5 μM for AS, and IABC of 2.2 g/l, pH7.9, and FD of 438.1 μM for FC, under which the predicted maximum SCA were 32.98 and 30.10 g/l using AS and FC, respectively. The predictions were close to validation experimental results, indicating that the models can be used to guide and optimize the flocculation of N. oculata using AS and FC as the flocculants.

Effect of carbon dioxide on the rheological behavior of submerged cultures of Chlorella minutissima in stirred tank reactors

The objective of this study was to quantify the effect of algal biomass concentration on the rheology of the algal culture broth. Batch cultivations of Chlorella minutissima were carried out with air and carbon dioxide in a stirred tank bioreactor with a working volume of 1.8 L. The apparent viscosity of the culture broth was significantly affected by the cell mass concentrations in the bioreactor. Culture broth containing 50 g/L cell mass from air fed was found to exhibit an apparent viscosity of 1.52 mPa.s. The apparent viscosity of the carbon‐dioxide‐fed cultivations was found to increase by 20% at a shear rate of 100 s−1. The flow behavior of the system was adequately described by the Herschel–Bulkley model with a small yield stress.

Modification, calibration and verification of the IWA River Water Quality Model to simulate a pilot-scale high rate algal pond

We implemented the IWA River Water Quality Model No. 1 (Reichert et al., 2001. River Water Quality Model No. 1, IWA Scientific & Technical Report No. 12) to simulate water-quality characteristics in two pilot-scale High Rate Algal Ponds. Simulation results were compared with two years' of data from the ponds. The first year's data from one pond were used for model calibration; the remaining data were used for validation. As originally formulated and parameterized, the model consistently yielded summer-time algal biomass concentrations which were too low – with consequent failures in its reproduction of dissolved oxygen, pH and nutrient dynamics. We experimented with various structural/parametric changes to improve the model's performance. The most effective strategy was to greatly increase the respiratory losses suffered by the heterotrophic osmotrophs (thereby giving the algae access to a larger fraction of the incoming dissolved organic carbon and nitrogen). This suggests that CO2-bubbling alone cannot entirely preclude resource-limitation of algal production. We doubt that our parameterization of heterotrophic osmotrophs is correct and infer that the algae derive a large fraction of their nutrition by direct osmotrophic uptake of dissolved organic matter. This inference is supported by the literature concerning the physiology of the dominant algal species in our ponds.

Composition and abundance of zooplankton community of an impacted estuarine lagoon in Northeast Brazil

Guaraíras Lagoon is a shallow coastal lagoon subject to intense human impacts, including shrimp aquaculture, urban expansion and agricultural activities, and is therefore vulnerable to eutrophication. With the aim of detecting the effects of human-mediated disturbance and environmental change in the lagoon, a spatial-temporal study was conducted in order to assess the actual ecological status of the lagoon and the species composition and density of the mesozooplankton, highlighting copepod assemblages. Algal biomass (chlorophyll-a) and total phosphorus concentration indicated that the lagoon is a meso-eutrophic coastal system in the inner part, and is oligotrophic in the areas influenced by the marine waters. High salinities were recorded in the lagoon, characterizing the lagoon as a coastal-marine ecosystem, rather than true estuarine. Mesozooplankton abundance fluctuated widely and showed marked spatial heterogeneity. The copepod assemblage was characterized by a coastal/estuarine group dominated by Oithona spp., Acartia lilljeborgi and Parvocalanus crassirostris in the inner areas of the lagoon, and a marine group characterized by the copepods Paracalanus quasimodo, Calanopia americana, Corycaeus (C.) speciosus and Monstrilloida in the area of marine influence. Thus, the spatial variability in the distribution of mesozooplankton species can be ascribed to the presence of a horizontal gradient of salinity and trophic conditions. Overall, the results showed that spatial variation in the water physicochemical characteristics of Guarairas Lagoon have significant effects on the structure and repartition of the mesozooplankton assemblages, which may potentially affect the functioning and biodiversity of this coastal ecosystem.

Biomass production and nutrient uptake by Neochloris oleoabundans in an open trough system

The purpose of this paper is to present biomass and nutrient uptake data from Neochloris oleoabundans production in an open trough system. The growth medium used was BG11, temperature ranged from 16.7 °C to 25.3 °C, and pH ranged from 5.52 to 9.94 because the customary pH increase during algal biomass production was moderated by incoming CO(2) gas streams (atmospheric, 2%, 4%, and 6% CO(2)). Peak concentrations of algal biomass ranged from 643 to 970 mg L(-1), specific growth rates ranged from 0.15 to 0.37 day(-1), and doubling times ranged from 4.8 to 1.9 days. Carbon, nitrogen, and phosphorus were incorporated into the biomass at 0.05%, 8.3%, and 54% of supplied amounts. Open growth systems supplemented with CO(2) should be designed to regulate medium pH within the range of 6.3 to 7.1. Future research should examine various media and alternative carbon sources to decrease doubling times, increase peak concentrations, and optimize nutrient uptake.

Experimental evidence that pollution with urea can degrade water quality in phosphorus‐rich lakes of the Northern Great Plains

Urea is the most abundant nitrogen (N) fertilizer used on agricultural soils, yet its effects on adjacent aquatic ecosystems are largely unknown. Here 21‐d, 3000‐liter mesocosm experiments were conducted monthly in a hypereutrophic lake during July–September 2007 to quantify how addition of urea might affect phytoplankton abundance, gross community composition, and algal toxicity in a phosphorus (P)‐rich lake. Repeated measures analysis of variance demonstrated that addition of sufficient urea to increase ratios of soluble N: P from ~ 15 : 1 to &gt; 24 : 1 (by mass) also increased algal biomass (as Chlorophyll ά) and microcystin concentrations 200–400%, as non–N2‐fixing but toxic cyanobacteria (Microcystis, Planktothrix) and less harmful chlorophytes (Micractinium, Oocystis) replaced colonial N2‐fixing cyanobacteria (Anabaena, Aphanizomenon). No significant effects of urea amendment were recorded for trials in which N: P ratios were elevated at the start of the experiment, or in which ambient light levels were reduced to 25 µmol quanta m−2 s−1, although preliminary evidence suggests that urea addition stimulated growth of heterotrophic bacteria irrespective of light regime. Development of toxic non–N2‐fixing cyanobacteria by N pollution of P‐rich lakes is consistent with findings from whole‐lake experiments and paleolimnological studies of deep lakes, and suggests that the fertilization needed to feed 3 billion more people by 2050 may create conditions in which future water quality in P‐replete regions is degraded further by urea export from farms and cities.

A hollow fiber membrane photo‐bioreactor for CO2 sequestration from combustion gas coupled with wastewater treatment: a process engineering approach

AbstractBACKGROUND: In the presence of light, micro‐algae convert CO2 and nutrients to biomass that can be used as a biofuel. In closed photo‐bioreactors, however, light and CO2 availability often limit algae production and can be difficult to control using traditional diffuser systems. In this research, a hollow fiber membrane photo‐bioreactor (HFMPB) was investigated to: (1) increase the interfacial contact area available for gas transfer, (2) treat high nutrient strength (412 mg NO3−‐N L−1) wastewater, and (3) produce algal biomass that can be used as a biofuel.RESULTS: A bench scale HFMPB was inoculated with Spirulina platensis and operated with a 2‐15% CO2 supply. A mass transfer model was developed and found to be a good tool to estimate CO2 mass transfer coefficients at varying liquid velocities. Overall mass transfer coefficients were 1.8 × 10−6, 2.8 × 10−6, 5.6 × 10−6m s−1 at Reynolds numbers of 38, 63, and 138, respectively. A maximum CO2 removal efficiency of 85% was observed at an inlet CO2 concentration of 2% and a gas residence time (membrane‐lumen) of 8.6 s. The corresponding algal biomass concentrations and NO3 removal efficiencies were 2131 mg L−1 and 68%, respectively.CONCLUSION: The results show that the combination of CO2 sequestration, wastewater treatment and biofuel production in an HFMPB is a promising alternative for greenhouse gas mitigation. Copyright © 2010 Society of Chemical Industry

Flocculation of microalgae using cationic starch

Due to their small size and low concentration in the culture medium, cost-efficient harvesting of microalgae is a major challenge. We evaluated the potential of cationic starch as a flocculant for harvesting microalgae using jar test experiments. Cationic starch was an efficient flocculant for freshwater (Parachlorella, Scenedesmus) but not for marine microalgae (Phaeodactylum, Nannochloropsis). At high cationic starch doses, dispersion restabilization was observed. The required cationic starch dose to induce flocculation increased linearly with the initial algal biomass concentration. Of the two commercial cationic starch flocculants tested, Greenfloc 120 (used in wastewater treatment) was more efficient than Cargill C*Bond HR 35.849 (used in paper manufacturing). For flocculation of Parachlorella using Greenfloc 120, the cationic starch to algal biomass ratio required to flocculate 80% of algal biomass was 0.1. For Scenedesmus, a lower dose was required (ratio 0.03). Flocculation of Parachlorella using Greenfloc 120 was independent of pH in the pH range of 5 to 10. Measurements of the maximum quantum yield of PSII suggest that Greenfloc 120 cationic starch was not toxic to Parachlorella. Cationic starch may be used as an efficient, nontoxic, cost-effective, and widely available flocculant for harvesting microalgal biomass.

Effects of biological and physical factors on seasonal oxygen dynamics in a stratified, eutrophic coastal ecosystem

Using a dual‐budget approach based on oxygen concentrations and stable isotopes, we examined primary production, respiration, and production to respiration ratios (P : R) across the Louisiana continental shelf to determine the relative roles of biological and physical factors in controlling seasonal oxygen dynamics. Regression models for δ18O and P :R indicated that the concentration of algal biomass explained most of the variability of the seasonal oxygen dynamics in surface waters. Physical factors, such as salinity, temperature, water‐column stability, and station depth were only of minor importance. Seasonal oxygen dynamics were more pronounced in bottom waters than in surface waters as hypoxia was common in bottom waters during summer months (May‐October). During cooler winter months (November‐April), oxygen concentrations throughout the water column were close to equilibrium with the atmosphere. The relative importance of benthic respiration to water‐column respiration in bottom waters was more pronounced during summer months when the water column was stratified. A strong physical disturbance caused by Hurricane Claudette during the summer of 2003 resulted in lower surface productivity relative to the calm 2001 and 2002 summertime conditions. Even though estimates of surface primary production and P :R were lower in July 2003 compared to July 2002, concentration of algal biomass (particulate organic carbon, C: N) remained the most important factor for d18O and P :R dynamics. The physical disturbance due to the hurricane, however, diminished the relative importance of benthic respiration, so that the system rather resembled wintertime conditions.

Effect of Lake Management Efforts on the Trophic State of a Subtropical Shallow Lake in Lakeland, Florida, USA

For more than a decade, Lakeland, FL, has invested in restoring its urban Lake Hollingsworth from a hypereutrophic state to its natural eutrophic state. The lake bottom was dredged of nearly 2 million m3 of accumulated organic sediments, and treatment wetlands, storm water curb inlet strainers, and a storm water baffle box were installed within the lake’s catchment area to reduce the loading of dirt, leaves, and trash to the lake. After dredging ceased, the lake was dosed one time with alum to improve water clarity and reduce phosphorus recycling from its sediments. Water quality surrogates for algal biomass— Secchi disk transparency and water column total nitrogen, total phosphorus, and chlorophyll-α concentrations— were reviewed to assess Lakeland’s progress towards its goal. In the years since dredging has stopped, algal biomass concentration in Lake Hollingsworth has significantly declined. Even with these improvements, however, the lake still remains hypereutrophic.

Nitrogen transformation processes in the Elbe River: Distinguishing between assimilation and denitrification by means of stable isotope ratios in nitrate

During a 9-day Lagrangian sampling campaign along the free-flowing section of the Elbe River in July 2005, water from the river as well as from major tributaries and sewage treatment plants was sampled to investigate major nitrogen transformation processes, focussing on denitrification and N-assimilation by phytoplankton. Samples were analysed for $$\delta^{15}N - NO^{-}_{3}$$ , $$\delta^{18}O - NO^{-}_{3}$$ , $$\delta^{15}N - NH^{+}_{4}$$ , nutrient concentrations, chlorophyll a (Chl a), and particulate organic matter. A strong decrease in nitrate concentration accompanied by strong increases in Chl a, particulate organic carbon (POC) and δ15N- and $$\delta^{18}O - NO^{-}_{3}$$ values were measured along the river. The ratio of the increase in δ15N vs. δ18O of the river nitrate samples was 0.89:1. Together with the observed decrease in nitrate and the increase in Chl a and POC, this indicates a major role of nitrogen assimilation by phytoplankton. This finding is supported by budget calculations, while nitrate inputs from the sampled tributaries and from sewage treatment plants were of minor importance for the nitrogen budget of the Elbe River. The stable isotope analysis of nitrogen and oxygen in nitrate is shown to be a powerful tool for the identification of N transformation processes along large rivers, particularly if combined with Lagrangian measurements of algal biomass, and dissolved and particulate nutrient concentrations.