Algal Biomass Growth Research Articles

Finding optimal algal/bacterial inoculation ratio to improve algal biomass growth with wastewater as nutrient source

Algal growth, nutrient removal and settling efficiency were quantified while inoculating sequencing batch reactors with a mixture of microalgae and bacteria (activated sludge). Three algae/bacteria inoculation ratios (5:1, 1:1 and 1:5) as well as pure algal biomass (control) were assessed. Algal biomass production increased with the addition of activated sludge. However, the addition of too much activated sludge can cause disturbance to the Al-Bac biomass growth and algal bacterial processes. All reactors including the control with only algae showed similar settling and nutrient removal efficiencies. Good settling was observed in all reactors with only 5% of total biomass found in supernatant after 1 h of settling. Removal efficiencies of COD, TN and PO4-P in all reactors were 79–82%, 61–65% and 15–37%, respectively, with the lowest phosphorus removal efficiency belonging to 1:5 algae/activated sludge ratio. These results may be due to both long hydraulic (7 days) and solids retention times (up to 30 days). Finally, Al-Bac biomass with 1:1 inoculation ratio showed the best enhancement in terms of biomass growth and algal activities.

The time delays influence on the dynamical complexity of algal blooms in the presence of bacteria

Bacteria associated with oceanic algal blooms are acknowledged to play important roles in carbon, nitrogen, and sulfur cycling. They influence the climate, mediate primary production, participate in biogeochemical cycles, and maintain ecological balance. A greater insight on the control of the interactions between microalgae and other microorganisms, particularly bacteria, would be helpful in exploring the role of bacteria on algal blooms in lakes. The present study is to investigate the effects of bacteria on the occurrence of algal blooms in lakes. We propose a nonlinear mathematical model by taking into account interactions among nutrients, algae, detritus and bacteria in a lake. We assume that bacteria enhance the growth of algal biomass through remineralization only. Equilibria are analyzed for feasibility and stability, substantiated via numerical simulations. Increase in uptake rate of nutrients by algae and bacteria death rate generates transcritical bifurcations. We perform a global sensitivity analysis to identify the important parameters of the model having a significant impact on the densities of algae and bacteria in the lake. Our findings show that massive algal production might occur in the presence of bacteria, and microalgae-bacteria interactions can be beneficial to the massive production of microalgae. Further, the effect of time delays involved in the bacterial decomposition conversion of detritus into nutrients is studied. Chaotic oscillations may arise via equilibrium destabilization on increasing the values of the time lag. To support chaos occurrence, the Poincaré map is drawn and the Lyapunov exponents are also computed. The findings, critically important for lake restoration, indicate that hypoxia in the lake can be prevented if detritus removal is performed on a regular basis, at time intervals smaller than the critical threshold in the delay with which detritus is decomposed into nutrients.

Biological manipulation of eutrophication in West Yangchen Lake

This paper aims to share findings on nonclassical biomanipulation from a field study on eutrophic West Yangcheng (WY) Lake. In the forty years before 2009, cyanobacteria frequently bloomed in WY Lake, an event which has not occurred since 2009. The stocking density of filter-feeding carp was estimated to be more than 50 g/m3 in July after 2009, approximately double the amount observed before 2009, and the ratio of silver carp to bighead carp (SBR) increased from 0.8 to more than 1.6. Compared with the water quality between 2004 and 2007, the total nitrogen (TN) and the chlorophyll-a (Chl-a) concentration decreased while total phosphorus (TP) and transparency (SD) increased significantly after 2009 (P < 0.05). The decreasing Chl-a concentration was observed in Jul, Jun, May, Jul, and Mar in 2009, 2010, 2011, 2016, and 2017, respectively. The Chl-a concentration was significantly negatively correlated with TP (P < 0.05), and no significant correlation with TN was observed (P > 0.05). A significant negative correlation was observed between fish yield and SD (P < 0.05). The results also showed that filter-feeding carp more effectively restrained algae growth when SD was low. These results indicated that a high density of filter-feeding fish with increased SBR interfered with the driving effects of nutrients and temperature on the growth of algal biomass and then restrained bloom of algae. It may be necessary to take SD into consideration for determining the appropriate fish stocking density for the biomanipulation of algae.

Evaluation of the performance of different materials to support the attached growth of algal biomass

The attached microalgal biomass production in wastewater is promising for the development of biofilm reactors aimed at the economic separation and harvesting of biomass. However, the current impasse in the attached algal biomass production relies on the ability of materials to support such adherence. This study evaluated the effects of different support materials on the production and composition of algal biomass cultivated in domestic sewage. Durability and adherence of algal biomass to the threads of the support material were the most important criteria for choosing the material with the best performance. Three support materials were evaluated: cotton, nylon, and polyester. Polyester presented the best results in terms of durability; its resistance to friction tests was the highest, and even increased after its use in the experiment; this was associated with the high biomass production, mostly after the biomass inoculum (50.1 g∙m−2). This support also demonstrated greater development of nitrifying bacteria, which are essential for biofilm formation due to the presence of filaments in their cells. As for biomass characterization, it was observed that the different support materials did not interfere in the composition of the cells present in the attached biomass.

Mathematical and Numerical Modeling of Microalgae Growth

This work concerns the mathematical and numerical modeling of microalgae growth in a photobioreactor. The model used is based on the one developed by Okpokwasili and Nweke in 2005, which is used to describe the influence of nutrients on the growth rate of microalgae. Okpokwasili and Nweke proposed two expressions to calculate the growth rate influenced by several limiting factors. In this work, a material balance and an energy equation are associated with the above-mentioned model in order to describe the change in concentration of algal biomass, nitrogen, phosphorus and inorganic carbon in the culture medium, assuming that the temperature and light intensity are constant. The Runge-Kutta method is used to solve the system of energy and mass equations. The presented model can be used for the simulation and the prediction of algal biomass growth over time. A simulation has been made by experimental data completed by data from literature for the two expressions of the growth rate; the results of the simulation are in agreement with the ones of experience.

Evaluation of gradual adaptation of mixed microalgae consortia cultivation using textile wastewater via fed batch operation

This study investigated mixed microalgae consortia cultivation in a fed batch reactor using textile wastewater. The results showed 95% of total phosphorus (TP) and 70% of total nitrogen (TN) depletion during the operational period. Algal biomass growth, pollutant removal, and biomass constituents were examined for five cycles of the fed batch operation. The length of the cycles decreased from 30 days to 10 days as the cycle repeated, which implied gradual adaptation of microalgae to textile wastewater. Color of textile wastewater was removed in the range of 68–72% in all the cycles experimented. Microbial algal cultivation with textile wastewater would be a feasible approach for remediation and resource recovery purpose.

Degradation of 3-nitro-1,2,4-trizole-5-one (NTO) in wastewater with UV/H2O2 oxidation

Insensitive Munition (IM) formulations contain 3-nitro-1,2,4-trizole-5-one (NTO), an energetic compound with the highest aqueous solubility (16 g L−1) among all IM explosives, including 2,4-dinitroanisole (DNAN) and 1-nitroguanidine (NQ); as a result wastewater streams from IM processing facilities can be highly contaminated and potentially toxic. The removal of energetic compounds from wastewater streams prior to their discharge in the environment is imperative, and new technology must be developed to efficiently treat high levels of NTO and other IM compounds in these streams. In this study, the treatment of NTO wastewater by a UV/H2O2 oxidation process under acidic conditions (pH = 3.0 ± 0.1) and a hydrogen peroxide concentration of at least 1500 mg L−1 resulted in successful removal of the energetic compound. The organic carbon from the NTO ring was completely converted to inorganic carbon (CO2), as confirmed through TOC measurements and GC–MS analysis on the reactor headspace. Nitrate and ammonium ions were the major nitrogen by-products, as indicated by mass spectrometry. The results obtained in this work demonstrate that the UV/H2O2 oxidation process can effectively mineralize high concentrations of NTO in wastewater streams leading to recovery of valuable nutrients that can be used for supporting algal biomass growth for biofuel/biogas generation.

Industrial wastewater treatment in internal circulation bioreactor followed by wetlands containing emergent plants and algae.

Wastewater treatment based on ecological principles is a low cost and highly desirable solution for the developing countries like Pakistan. The present study evaluated the effectiveness of biological treatment systems including Internal Circulation (IC) anaerobic bioreactor and constructed wetlands (CWs) containing macrophytes and mixed algal cultures for industrial wastewater treatment. The IC bioreactor reduced COD (52%), turbidity (89%), EC (24%) of the industrial wastewater. However, the effluents of IC bioreactor did not comply with National Environmental Quality Standards (NEQS) of Pakistan. Post-treatment of IC bioreactor effluents was accomplished in CW containing macrophytes (Arundo donax and Eichhornia crassipes) and mixed algal culture. The CWs planted with macrophytes lowered the concentrations of COD (89%) and turbidity (99%). CWs with algal biomass were not effective in further polishing the effluent. Inhibition of algal biomass growth was observed due to physicochemical characteristics of wastewater. The integrated treatment system consisting of IC bioreactor and macrophytes was found more suitable option for industrial wastewater treatment.

The influence of temperature on algal biomass growth for biogas production

The use of algae is gaining popularity in recent years. Algae can form a suitable substrate for biogas production because they are low in cellulose and have low lignin content. The paper contains a summary with the list of the algae species applied for the biogas production process to this date, coupled with the description of the characteristic conditions in which the process is conducted. The key importance factors during the production of biogas include, among others, grade of algae species used, temperature of the process, mode in which the material is supplied into the tank, mixing method, use of co-substrate, etc. This paper reports the results of the study involving the effect of various temperature conditions on the characteristics of the growth rate of algal biomass. The research was performed for the Chlorella vulgaris BA-0167 strain in the temperature range corresponding to the mesophilic fermentation processes in anaerobic conditions.

Dynamic modeling of green algae cultivation in a photobioreactor for sustainable biodiesel production.

Biodiesel produced from microalgae has been extensively studied due to its potentially outstanding advantages over traditional transportation fuels. In order to facilitate its industrialization and improve the process profitability, it is vital to construct highly accurate models capable of predicting the complex behavior of the investigated biosystem for process optimization and control, which forms the current research goal. Three original contributions are described in this paper. Firstly, a dynamic model is constructed to simulate the complicated effect of light intensity, nutrient supply and light attenuation on both biomass growth and biolipid production. Secondly, chlorophyll fluorescence, an instantly measurable variable and indicator of photosynthetic activity, is embedded into the model to monitor and update model accuracy especially for the purpose of future process optimal control, and its correlation between intracellular nitrogen content is quantified, which to the best of our knowledge has never been addressed so far. Thirdly, a thorough experimental verification is conducted under different scenarios including both continuous illumination and light/dark cycle conditions to testify the model predictive capability particularly for long-term operation, and it is concluded that the current model is characterized by a high level of predictive capability. Based on the model, the optimal light intensity for algal biomass growth and lipid synthesis is estimated. This work, therefore, paves the way to forward future process design and real-time optimization.

Growth of algal biomass in laboratory and in large-scale algal photobioreactors in the temperate climate of western Germany

Growth of Chlorella vulgaris was characterized as a function of irradiance in a laboratory turbidostat (1L) and compared to batch growth in sunlit modules (5–25L) of the commercial NOVAgreen photobioreactor. The effects of variable sunlight and culture density were deconvoluted by a mathematical model. The analysis showed that algal growth was light-limited due to shading by external construction elements and due to light attenuation within the algal bags. The model was also used to predict maximum biomass productivity. The manipulative experiments and the model predictions were confronted with data from a production season of three large-scale photobioreactors: NOVAgreen (<36,000L), IGV (2,500–3,500L), and Phytolutions (28,000L). The analysis confirmed light-limitation in all three photobioreactors. An additional limitation of the biomass productivity was caused by the nitrogen starvation that was used to induce lipid accumulation. Reduction of shading and separation of biomass and lipid production are proposed for future optimization.

Mathematical modeling of the dynamic behavior of an integrated photo-bioelectrochemical system for simultaneous wastewater treatment and bioenergy recovery

An integrated photo-bioelectrochemical (IPB) system is innovative through integrating microbial fuel cells (MFCs) with algal bioreactors for simultaneous organics degradation, nutrient removal, and bioenergy production. A mathematical model has been developed for simulating and understanding the performance of the IPB system. The model inputs include influent COD (chemical oxygen demand), NH4+-N, total phosphorus, external resistance and flow rate, while the outputs include the biomass growth, COD degradation, nutrient removal, and electricity generation. The determination of unknown model parameters was assisted with sensitivity analysis. Satisfactory model fitting and validation was achieved, with low root-mean-square error of 5.6% and 0.2%, respectively, for biomass concentration and current generation under varied COD input. The simulated results suggested that the organic input and flow rate had more significant impacts on the growth of algal biomass than other input factors, while COD, flow rate and external resistance were of importance for current generation. The optimal condition for improving this particular IPB system was predicted to have a COD concentration above 150 mg L−1 and the flow rate at 0.1 mL min−1. This IPB model is the first attempt of the kind for the optimization of an integrated bioprocess of electrochemical reactions and algal growth.

A Sustainable Partnership for Algal Biofuel Production and Waste Treatment for Cogeneration of Energy and Co-products

Background: Algal biofuel production can be made sustainable in partnership with dairy farms, industries and municipal systems for nutrient management requiring waste treatment. Waste streams contain unmined nutrients such as nitrogen, phosphorus, and carbon. The nutrients runoff especially nitrogen and phosphorus pollution can impair water quality of natural water bodies posing environmental threat due to undesirable algae blooms affecting natural aquatic communities. Anaerobic biodigesters can efficiently take care of biochemical oxygen demand to improve water quality but leave behind excess nutrients in the effluent. The excess nutrients can be potentially used for selected algal biomass growth for fuel and co-products. Methods: This paper reviews the algal biofuel systems that can integrate with biodigesters for sustainable cogeneration of renewable energy forms (liquid biofuels, electricity, and heat) so that the waste effluent from dairy farms, municipal and industrial anaerobic digesters, food and beverage and other industries can be combined with the algal biofuel process to produce additional valued co-products including feedstock for biogas, organic fertilizer, and animal feed for generating additional revenues. Conclusion: A successful implementation of a system as described will have multifold higher oil yield from non-food algae biomass compared to food sources (e.g. soybean and corn oil) for biofuel; benefit environment by capturing nitrogen and phosphorus from effluents to reduce environmentally harmful runoff affecting the health of natural water bodies, reduce in the fuel emissions especially the oxides of nitrogen in contrast to both diesel and conventional biodiesel, meet environmental protection regulations with reductions in particulate matter and total hydrocarbons; and bring economic benefits from marketable products across the complete supply chain involved at the sites that implement bolt on algal system with waste management systems for cogeneration of energy. Keywords: Algae, wastewater, nutrients, biofuel, cogeneration, digester, renewable diesel, fertilizer, animal feed, co-products.

Self-sustainable electricity production from algae grown in a microbial fuel cell system

This paper describes the potential for algal biomass production in conjunction with wastewater treatment and power generation within a fully biotic Microbial Fuel Cell (MFC). The anaerobic biofilm in the anodic half-cell is generating current, whereas the phototrophic biofilm on the cathode is providing the oxygen for the Oxygen Reduction Reaction (ORR) and forming biomass. The MFC is producing electricity with simultaneous biomass regeneration in the cathodic half-cell, which is dependent on the nutrient value of the anodic feedstock. Growth of algal biomass in the cathode was monitored, assessed and compared against the MFC power production (charge transfer), during this process. MFC generation of electricity activated the cation crossover for the formation of biomass, which has been harvested and reused as energy source in a closed loop system. It can be concluded that the nutrient reclamation and assimilation into new biomass increases the energy efficiency. This work is presenting a simple and self-sustainable MFC operation with minimal dependency on chemicals and an energy generation system utilising waste products and maximising energy turnover through an additional biomass recovery.

Effect of lake water on algal biomass and microbial community structure in municipal wastewater-based lab-scale photobioreactors.

Photobioreactors are a novel environmental technology that can produce biofuels with the simultaneous removal of nutrients and pollutants from wastewaters. The aim of this study was to evaluate the effect of lake water inoculation on the production of algal biomass and phylogenetic and functional structure of the algal and bacterial communities in municipal wastewater-treating lab-scale photobioreactors. Inoculating the reactors with lake water had a significant benefit to the overall algal biomass growth and nutrient reduction in the reactors with wastewater and lake water (ratio 70/30 v/v). The metagenome-based survey showed that the most abundant algal phylum in these reactors was Chlorophyta with Scenedesmus being the most prominent genus. The most abundant bacterial phyla were Proteobacteria and Bacteroidetes with most dominant families being Sphingobacteriaceae, Cytophagaceae, Flavobacteriaceae, Comamonadaceae, Planctomycetaceae, Nocardiaceae and Nostocaceae. These photobioreactors were also effective in reducing the overall amount of pathogens in wastewater compared to reactors with wastewater/tap water mixture. Functional analysis of the photobioreactor metagenomes revealed an increase in relative abundance genes related to photosynthesis, synthesis of vitamins important for auxotrophic algae and decrease in virulence and nitrogen metabolism subsystems in lake water reactors. The results of the study indicate that adding lake water to the wastewater-based photobioreactor leads to an altered bacterial community phylogenetic and functional structure that could be linked to higher algal biomass production, as well as to enhanced nutrient and pathogen reduction in these reactors.

Biosequestration of CO2 using power plant algae (Rhizoclonium hieroglyphicum JUCHE2) in a Flat Plate Photobio-Bubble-Reactor – Experimental and modeling

Biosequestration of CO2 in a 1.8L Flat Plate Photobio-Bubble-Reactor using power plant algae (Rhizoclonium hieroglyphicum JUCHE2) has been studied. CO2 concentration and light intensity have been varied in the range of 5–25% and 82μmolm−2s−1–398.71μmolm−2s−1, respectively. Dependence of initial specific growth rate of algae has been explained by Haldane type kinetics and by Langmuir–Hinshelwood type kinetics including shape factor with respect to liquid phase CO2 concentration and the intensity of light, respectively. Half saturation constants for CO2 (=Ks) and light (=KE), inhibition constant for CO2 (=KI) and maximum specific growth rate (=μmax) have been determined, respectively as 1.25×10−7Mol/L, 120μmolm−2s−1, 0.00165Mol/L and 0.996d−1. A mathematical model of the Flat Plate Photobio-Bubble-Reactor has been developed incorporating effects of phenomena like gas to liquid mass transfer of CO2, stripping of dissolved CO2 to overhead gas space of the reactor, CO2 uptake by algal biomass. Population dynamics of long term growth of algal biomass have been incorporated by using a Gaussian time function. The model has been validated up to gas phase CO2 concentration of 25% through successful comparison of predicted data with corresponding experimental results.

Biodiesel from wastewater: lipid production in high rate algal pond receiving disinfected effluent.

The production of different species of microalgae in consortium with other micro-organisms from wastewaters may represent an alternative process, to reduce the costs, for obtaining biofuels. The aim of this study was to evaluate the influence of pre-ultraviolet disinfection (UV) in the production of lipids from biomass produced in high rate ponds. Two high rate algal ponds were evaluated: a pond that received domestic sewage without disinfection and the other receiving domestic sewage previously disinfected by UV radiation (uvHRAP). The UV disinfection did not lead to significant differences in fatty acid profile and total lipid productivities, although it increased algal biomass concentration and productivity as well as lipid content. Moreover, the overall biomass concentrations and productivities decreased with the UV disinfection, mostly as a consequence of a loss in bacterial load. We thus conclude that uvHRAP disinfection may represent a potential strategy to promote the cleaner and safer growth of algal biomass when cultivated in consortium with other micro-organisms. Mainly regarding the use of wastewater as culture medium, together with a cheaper production of lipids for biodiesel, pre-disinfection may represent an advance since extraction costs could be significantly trimmed due to the increase in lipid content.

Algal biocathode for in situ terminal electron acceptor (TEA) production: synergetic association of bacteria-microalgae metabolism for the functioning of biofuel cell.

Replacement of energy intensive mechanical aeration with sustainable oxygenic photosynthesis by microalgae at cathode was studied in dual-chambered microbial fuel cell (MFC). The synergistic association between bacterial fermentation at anode and the oxygenic photosynthesis of microalgae at cathode facilitated good power output as well as treatment efficiency. However, MFC operation during spring showed higher bioelectrogenic activity (57.0 mW/m(2)) over summer (1.1 mW/m(2)) due to the higher oxygenic photosynthetic activity of microalgae and respective dissolved oxygen (DO) levels. This can be attributed to RuBisCO inactivation under high temperatures and light intensity of summer, which prevented rich algal biomass growth as well as their photosynthetic activity. Unlike abiotic cathode, the algal cathode potential increased with operation time due to the algal biomass growth during spring but was negligible during summer. The catalytic currents on voltammetric signatures and the bioprocess parameters also corroborated well with the observed power output.

Growth of microalgal biomass on supernatant from biosolid dewatering

The paper reports the results of an experiment to assess the feasibility of including a photobioreactor within the design of a wastewater treatment plant, growing microalgae on the centrate from anaerobic sludge dewatering. The growth of algal biomass would take advantage of the available nitrogen and provide a substrate for biogas production by anaerobic digestion. Tests were carried out by semi-continuously feeding a photobioreactor with a centrate-effluent blend and by increasing the fraction of centrate. The experimental results show that the centrate does not induce any toxicity and, on the contrary, can be well utilized by microalgae, whose average specific growth rate (μ), on centrate as such, was between 0.04 and 0.06 d(-1). The maximum biomass concentration in the photobioreactor effluent was 1.6 gSS/L at 10 days HRT (hydraulic retention time). Methane production tests led to biochemical methane production values of 335 ± 39, and 284 ± 68 mL 0°C, 1 atm CH4/g VS for the two tested samples, in agreement with literature values. Settling tests show that the settling capacity of microalgae, although satisfactory, could be effectively improved after mixing with activated sludge, confirming the potential to use the existing primary settler for microalgae thickening in order to feed microalgae for anaerobic digestion with primary/secondary sludge.

Optimize Flue Gas Settings to Promote Microalgae Growth in Photobioreactors via Computer Simulations

Flue gas from power plants can promote algal cultivation and reduce greenhouse gas emissions(1). Microalgae not only capture solar energy more efficiently than plants(3), but also synthesize advanced biofuels(2-4). Generally, atmospheric CO2 is not a sufficient source for supporting maximal algal growth(5). On the other hand, the high concentrations of CO2 in industrial exhaust gases have adverse effects on algal physiology. Consequently, both cultivation conditions (such as nutrients and light) and the control of the flue gas flow into the photo-bioreactors are important to develop an efficient "flue gas to algae" system. Researchers have proposed different photobioreactor configurations(4,6) and cultivation strategies(7,8) with flue gas. Here, we present a protocol that demonstrates how to use models to predict the microalgal growth in response to flue gas settings. We perform both experimental illustration and model simulations to determine the favorable conditions for algal growth with flue gas. We develop a Monod-based model coupled with mass transfer and light intensity equations to simulate the microalgal growth in a homogenous photo-bioreactor. The model simulation compares algal growth and flue gas consumptions under different flue-gas settings. The model illustrates: 1) how algal growth is influenced by different volumetric mass transfer coefficients of CO2; 2) how we can find optimal CO2 concentration for algal growth via the dynamic optimization approach (DOA); 3) how we can design a rectangular on-off flue gas pulse to promote algal biomass growth and to reduce the usage of flue gas. On the experimental side, we present a protocol for growing Chlorella under the flue gas (generated by natural gas combustion). The experimental results qualitatively validate the model predictions that the high frequency flue gas pulses can significantly improve algal cultivation.