Algal Consortium Research Articles

Bioelectricity generation using sulphate-reducing bacteria as anodic and microalgae as cathodic biocatalysts

ABSTRACTBecause microalgal species carry out oxygenic photosynthesis, they can be employed in the cathode chamber of microbial fuel cells, thus negating the need for mechanical aeration for oxygen reduction reactions. A conventional H-shaped configuration is used for comparative analysis of bioelectricity generation using pure and mixed microalgal cultures. Three reactors are simultaneously inoculated with sulphate-reducing bacteria as anodic and mixed culture of microalgae (MA#1) and two pure species in the cathodic chamber in separate reactors (MA#2; MA#3). Maximum open circuit potentials of 670, 476 and 529 mV are achieved with MA#3, MA#2 and MA#1, respectively. Power densities on the order of 442.5, 69 and 135 mW/m3 are obtained for microalgal cultures MA#3, MA#2 and MA#1, respectively. The highest power and current density values are obtained with MA#3 inoculated with pure algal species. The algal species are also examined for their lipid content with the use of Fourier transform infrared spectroscopy, Nile red spectroscopy and lipid content analysis. A good amount of lipid content is shown in spectroscopy images. Biomass content is highest for the algal consortium (MA#1) whereas lipid content is best in the case of pure algal species (MA#2).

Cultivation of native algal consortium in semi-continuous pilot scale raceway pond for greywater treatment coupled with potential methane production

The native algal consortium, collected from wastewater pond, was grown in greywater and the process was scaled up in open ponds raceway (800L). It showed good growth along with removal of various nutrients concentration such as ammonia, nitrate, dissolved phosphate and sCOD below safe discharge limits, in both batch (flask study) and raceway ponds. The algal biomass thus obtained was rich in lipid (45.87% TS). The estimated theoretical methane potential was 745.87mL CH4 g−1 VS while experimental cumulative yield of up to 630mL CH4 g−1 VS (calculated based on the VS conversion into methane during anaerobic digestion) was observed during 30 d anaerobic digestion of algal biomass. The digestibility of the algal biomass was low (37%) with only 44% volatile solid reduction. The tested consortium has good potential for wastewater treatment coupled with substantial biomass production. However, further attempts for pretreatment and codigestion are essential to improve the methane yield and digestibility of the tested algal biomass.

Review of the harvesting and extraction program within the National Alliance for Advanced Biofuels and Bioproducts

Energy-efficient and scalable harvesting and lipid extraction processes must be developed in order for the algal biofuels and bioproducts industry to thrive. The major challenge for harvesting is the handling of large volumes of cultivation water to concentrate low amounts of biomass. For lipid extraction, the major energy and cost drivers are associated with disrupting the algae cell wall and drying the biomass before solvent extraction of the lipids. Here we review the research and development conducted by the Harvesting and Extraction Team during the 3-year National Alliance for Advanced Biofuels and Bioproducts (NAABB) algal consortium project. The harvesting and extraction team investigated five harvesting and three wet extraction technologies at lab bench scale for effectiveness, and conducted a techoeconomic study to evaluate their costs and energy efficiency compared to available baseline technologies. Based on this study, three harvesting technologies were selected for further study at larger scale. The selected harvesting technologies: electrocoagulation, membrane filtration, and ultrasonic harvesting, were evaluated in a field study at minimum scale of 100L/h. None of the extraction technologies were determined to be ready for scale-up; therefore, an emerging extraction technology (wet solvent extraction) was selected from industry to provide scale-up data and capabilities to produce lipid and lipid-extracted materials for the NAABB program. One specialized extraction/adsorption technology was developed that showed promise for recovering high value co-products from lipid extracts. Overall, the NAABB Harvesting and Extraction Team improved the readiness level of several innovative, energy efficient technologies to integrate with algae production processes and captured valuable lessons learned about scale-up challenges.

Lipid enhancement in microalgae by temporal phase separation: Use of indigenous sources of nutrients

Abstract Microalgae have been recommended as superior candidate for fuel production because of their advantages of higher photosynthetic efficiency, biomass & lipid productivity, and faster growth rate as compared to other energy crops. To meet up all these criteria, we have developed a continuous outdoor micro-algal raceway pond reactor (RPR) and a lab scale indoor tubular photo bioreactor (PBR) for biofuel production. An attempt to utilise indigenous sources of nutrients to improve the economics also revealed that micro-algal culturing can also be used as a mode of nutrient removal and water treatment. The photosynthetic rate and lipid production were enhanced by arresting daytime cell division and promoting night-time cell division. A 50% lipid improvement was observed for the particular algal consortia. Microscopic studies revealed that temporal phase separation could be achieved by adjusting nutrient distribution pattern. To monitor temporal phase separation, it is required to know DNA multiplication model. Quantification of gDNA in RPR confirmed that cell division happens during the night which positively affects the photosynthetic efficiency and lipid productivity of microalgae.

Bioremediation efficacy\u2014comparison of nutrient removal from an anaerobic digest waste-based medium by an algal consortium before and after cryopreservation

An algal consortium was isolated from an integrated steelmaking site at TATA Steel Strip Products Ltd. in Port Talbot, UK, and its bioremediation capacity tested. Excellent “bioremediation” was observed when the mixed culture was “applied” to diluted effluent from an enhanced anaerobic digestion plant at Dŵr Cymru Welsh Water at Port Talbot, UK. After 5 days of cultivation in a 600-L photobioreactor, 99% of the total nitrogen (initial level, 4500 μmol L−1) and total phosphorus (initial level, 690.4 μmol L−1) were removed from the waste stream. The consortium was deposited in the Culture Collection of Algae and Protozoa (CCAP), an international depository authority for microalgal patents, as CCAP 293/1. This material has been successfully cryopreserved using a two-step cryopreservation protocol with dimethyl sulphoxide (5% v/v) used as a cryoprotectant. On recovery of samples after 3 months storage at −196 °C, the specific bioremediation activity of the revived consortium was tested. The capacity of the revived culture to bioremediate effluent was not significantly different (p < 0.05) from a non-cryopreserved control, with 99% of total nitrogen and phosphorus remediated by day 4. Although non-axenic algal cultures have previously been cryopreserved, this is the first report of the successful cryopreservation of mixed algal consortium, with validation of its ability to bioremediate after thawing comparing non-cryopreserved cultures with a revived post-thaw algal consortium. The study also highlights the need to ensure the long-term security and the requirement to validate the functionality of conserved inocula with biotechnological/bioremediation potential.

Role of Algal Consortium for Treatment of Primary Effluent: An Approach towards Nutrient Removal and Biomass Production

Role of Algal Consortium for Treatment of Primary Effluent: An Approach towards Nutrient Removal and Biomass Production

Parboiled rice effluent: A wastewater niche for microalgae and cyanobacteria with growth coupled to comprehensive remediation and phosphorus biofertilization

The potential of microalgae and cyanobacteria for bioremediation of wastewater by nutrient uptake combined with simultaneous biomass production is a well recognized perception of today's world. The present study illustrates the treatment of a highly polluted wastewater generated during parboiling of paddy in rice mill industries, widely operational in developing countries where rice is the staple food crop, with the help of microalgal and cyanobacterial isolates capable of growing at high rates in parboiled rice mill effluent (RME). This endeavor leads to comprehensive bioremediation of the said effluent and subsequent use of the harvested biomass as slow release phosphorus biofertilizers and the treated effluent for crop irrigation. The RME-acclimatized algal consortium demonstrated highest growth in terms of fresh weight and greatest remediation efficiency at the end of 36days' treatment of RME, with 93.9% phosphorus and 100% ammonia-nitrogen removal, 98.7%, 91.6% and 93.5% reduction in biological oxygen demand, chemical oxygen demand and total dissolved solid, respectively, and an increment of 186±0.3mgL−1 dissolved oxygen, bringing down the pollutants level well below the discharge limits suggested by Central Pollution Control Board, India. Additionally, microalgae in the consortium aggregated in clumps spontaneously in presence of the filaments of Phormidium sp. facilitating easy harvest. The RME-acclimatized algal consortium demonstrated highest accumulation of polyphosphate (poly-P) (0.76±0.01% of dry weight) as well as highest release of phosphorus in non-sterile soil emphasizing the essential role of soil phosphorus solubilizing organisms to leach soluble phosphorus from the insoluble poly-P present in the biomass. The rice seedlings watered with treated RME also showed improved growth effect on shoot height and leaf width. The study results establish the suitability of RME as an excellent growth media for microalgae and cyanobacteria.

Performance of an algal-bacterial system for treatment of biomass gasifier wastewater in a 16-L RBC at 36 h HRT

Wastewater generated during gasification of biomass contains phenolics, nitrogen heterocyclics and polynuclear aromatic hydrocarbons (PAHs). In this work a sessile freshwater algal consortium and Exiguobacterium aurantiacum (3:1 v/v) was used for forming biofilm in a three stage 16-L RBC for treatment of gasifier wastewater having initial COD of 1381±50 mg/L. Biofilm formation was achieved through gradual acclimatization to gasifier wastewater before conducting flow-through studies at 36 h hydraulic retention time (HRT). COD removal in the first, second and third stage were 65±5%, 76±5% and 83±5%, respectively at pseudo steady state. Microalgae in the biofilm were predominantly comprised of green algae.

Organic carbon, influent microbial diversity and temperature strongly influence algal diversity and biomass in raceway ponds treating raw municipal wastewater

Algae based wastewater treatment coupled to biofuel production has financial benefits and practical difficulties. This study evaluated the factors influencing diversity and growth of indigenous algal consortium cultivated on untreated municipal wastewater in a high rate algal pond (HRAP) for a period of 1year using multivariate statistics. Diversity analyses revealed the presence of Chlorophyta, Cyanophyta and Bacillariophyta. Dominant microalgal genera by biovolume in various seasons were Scenedesmus sp., Microcystis sp., and Chlorella sp. Scenedesmus sp., persisted throughout the year but none of three strains co-dominated with the other. The most significant factors affecting genus dominance were temperature, inflow cyanophyta and organic carbon concentration. Cyanophyta concentration affected microalgal biomass and diversity, whereas temperature impacted biomass. Preferred diversity of microalgae is not sustained in wastewater systems but is obligatory for biofuel production. This study serves as a guideline to sustain desired microalgal consortium in wastewater treatment plants for biofuel production.

Combining urban wastewater treatment with biohydrogen production – An integrated microalgae-based approach

The aim of the present work was the simultaneous treatment of urban wastewater using microalgae and the energetic valorization of the obtained biomass. Chlorella vulgaris (Cv), Scenedesmus obliquus (Sc) and a naturally occurring algal Consortium C (ConsC) were grown in an urban wastewater. The nutrient removals were quite high and the treated water fits the legislation (PT Dec-Lei 236/98) in what concerns the parameters analysed (N, P, COD). After nutrient depletion the microalgae remained two more weeks in the photobioreactor (PBR) under nutritional stress conditions, to induce sugar accumulation (22–43%). The stressed biomass was converted into biohydrogen (bioH2), a clean energy carrier, through dark fermentation by a strain of the bacteria Enterobacter aerogenes. The fermentation kinetics were monitored and fitted to a modified Gompertz model. The highest bioH2 production yield was obtained for S. obliquus (56.8mL H2/gVS) which was very similar when using the same algae grown in synthetic media.

Growth of an Indigenous Algal Consortium on Anaerobically Digested Municipal Sludge Centrate: Photobioreactor Performance and Modeling

Centrate from dewatering anaerobically digested municipal sludge is a particular concern in wastewater treatment, as it contains high ammonia concentrations and is often recycled to the head of the plant, reducing efficiency. Algae have the potential to remove ammonia from this wastewater, while producing biomass that can be used as an energy feedstock. In this research, an indigenous algal consortium was cultivated on municipal sludge centrate in a semi-continuous photobioreactor under natural light conditions. The goals of this research were to (1) enrich an algal consortium capable of growth on sludge centrate; (2) determine the main species of the consortium;(3) measure biomass, lipid production, and nutrient removal rates; and (4) develop a simple model to describe the system. The results suggested that Chlorella sp. was the dominant species (95 %) in the consortium. Mean biomass productivity was 5.2 g m−2 day−1, which was relatively high compared with other studies carried out with high ammonia strength wastewaters. Lipid production was low, comprising only 10 % of total biomass. The algal consortium effectively removed nutrients from the centrate, with observed mean removal efficiencies for total nitrogen, total phosphorus, and chemical oxygen demand of 65, 72, and 8 %, respectively. A simple irradiance-based model was developed from the fundamental Michaelis-Menten photosynthesis-irradiance (PI) response for photosynthetic organisms. A good fit to the experimental data was obtained with the irradiance-based model (R2 = 0.96), indicating that the system was light limited. The results show that biomass production can be predicted based on irradiance only.

TESTING OF CHLORELLA/SCENEDESMUS MICROALGAE CONSORTIA FOR REMEDIATION OF WASTEWATER, CO₂ MITIGATION AND ALGAE BIOMASS FEASIBILITY FOR LIPID PRODUCTION

Industry, transport and unsustainable agriculture result in the increased quantity of wastewater, release of nutrients and emission of carbon dioxide that promotes eutrophication of water bodies and global climate change. the application of microalgae for phycoremediation, their biomass use for human needs may increase sustainability and have a positive effect on the regional development. The experiments were carried out in order to establish the feasibility of treating the local municipal wastewater with microalgae consortia and their biomass potential for biofuel production. The results revealed that Chlorella/Scenedesmus consortium eliminated up to 99.7–99.9% of inorganic phosphorus and up to 88.6–96.4% of inorganic nitrogen from the wastewater within three weeks. The ammonium removal was more efficient than that of nitrate. Chlorella algae grew better in diluted, while Scenedesmus – in the concentrated wastewater. The consortium treated wastewater more efficiently than a single species. The maximum biomass (3.04 g/L) of algal consortium was estimated in concentrated wastewater. Algae accumulated 0.65–1.37 g of CO2/L per day in their biomass. Tus, Chlorella/Scenedesmus consortium is a promising tool for nutrients elimination from the local wastewater under the climatic conditions specific to Lithuania. However, none of the two species were able to accumulate lipids under the nitrogen starvation conditions.

Nutrient Removal and Biofuel Production in High Rate Algal Pond Using Real Municipal Wastewater

This study evaluated the growth and nutrient removal ability of an indigenous algal consortium on real untreated municipal wastewater in a high rate algal pond (HRAP). The HRAP was operated semicontinuously under different hydraulic retention times (HRT: 2, 4, 6, and 8 days). The average removal efficiencies of chemical oxygen demand, and total nitrogen and phosphate of real municipal wastewater were maintained at 85.44 ± 5.10%, 92.74 ± 5.82%, and 82.85 ± 8.63%, respectively, in 2 day HRT. Algae dominated the consortium and showed high settling efficiency (99%), and biomass and lipid productivity of 0.500 ± 0.03 g/l/day and 0.103 ± 0.0083 g/l/day (2 day HRT), respectively. Fatty acid methyl ester analysis revealed a predominance of palmitate (C16:0), palmitoleate (C16:1), linoleate (C18:2), and linolenate (C18:3). Microalgal diversity analyses determined the presence of Chlorella, Scenedesmus, and Stigeoclonium as the dominant microalgae. The algal consortium provides significant value not only in terms of energy savings and nutrient removal but also because of its bioenergy potential as indicated by the lipid content (20-23%) and FAME profiling.

Antimicrobial hyperbranched poly(ester amide)/polyaniline nanofiber modified montmorillonite nanocomposites

There has been growing interest in the use of nanomaterials featuring potent of antimicrobial activity in the biomedical domain. It still remains a challenge for the researchers to develop an efficient nanocomposite possessing antimicrobial efficacy against broad spectrum microbes including bacteria, fungi as well as algal consortium, posing serious challenges for the human survival. In addressing the above problem, we report the fabrication of bio-based hyperbranched poly(ester amide) (HBPEA)/polyaniline nanofiber modified montmorillonite (MMT) nanocomposites by an ex-situ polymerization technique at varied weight percentages (1, 2.5, 5wt.%) of the modified MMT (nanohybrid). The Fourier transform infrared spectroscopy confirmed the structural changes upon interaction of the nanohybrid with HBPEA. A probable mechanism is proposed for the formation of nanocomposites with partially exfoliated nanoplatelet structure, which was further confirmed from the high resolution transmission electron microscopic analyses. The prepared nanocomposites exhibited potent efficacy against gram positive bacteria like Bacillus subtilis and Staphylococcus aureus as compared to the gram negative ones like Pseudomonas aeruginosa and Escherichia coli. The nanocomposites showed significant antifungal activity against Aspergillus niger, Fusarium oxysporum and Coleotricum capcii and antialgal activity against algal consortium comprising of Chlorella, Hormidium and Cladophorella species. The formation of thermosetting nanocomposites resulted in the acceptable improvement of desired physico-chemical and mechanical properties including thermostability. Thus pronounced antimicrobial activity of the nanocomposites against a spectrum of bacterial and fungal strains as well as a consortium of algal species along with other desired performance vouched them as potent antimicrobial materials in the realm of health and biomedical industry.

Growth and nitrogen removal capacity of Desmodesmus communis and of a natural microalgae consortium in a batch culture system in view of urban wastewater treatment: Part I

The microalgal biomass applications strongly depend on cell composition and the production of low cost products such as biofuels appears to be economically convenient only in conjunction with wastewater treatment. As a preliminary study, in view of the development of a wastewater treatment pilot plant for nutrient removal and algal biomass production, a biological wastewater system was carried out on a laboratory scale growing a newly isolated freshwater algal strain, Desmodesmus communis, and a natural consortium of microalgae in effluents generated by a local wastewater reclamation facility. Batch cultures were operated by using D. communis under different growth conditions to better understand the effects of CO2, nutrient concentration and light intensity on the biomass productivity and biochemical composition. The results were compared with those obtained using a natural algal consortium. D. communis showed a great vitality in the wastewater effluents with a biomass productivity of 0.138–0.227 g L−1 d−1 in the primary effluent enriched with CO2, higher biomass productivity compared with the one achieved by the algal consortium (0.078 g L−1 d−1). D. communis cultures reached also a better nutrient removal efficiency compared with the algal consortium culture, with almost 100% for ammonia and phosphorous at any N/P ratio characterizing the wastewater nutrient composition. Biomass composition was richer in polysaccharides and total fatty acids as the ammonia concentration in the water decreased. In view of a future application of this algal biomass, due to the low total fatty acids content of 1.4–9.3 wt% and the high C/N ratio of 7.6–39.3, anaerobic digestion appeared to be the most appropriate biofuel conversion process.

Use of an algal consortium of five algae in the treatment of landfill leachate using the high-rate algal pond system

Five species of microalgae Chlorella vulgaris, Scenedesmus quadricauda, Euglena gracilis, Ankistrodesmus convolutus and Chlorococcum oviforme, were screened for their ability to grow in treated landfill leachate (TL) using shake flask cultures. The treated leachate had undergone previous treatment through mechanical aeration in treatment ponds at the landfill site. The five algae, except for C. oviforme, were able to grow in medium containing up to 50% TL. Two high-rate algal ponds (HRAP) equipped with paddlewheel were used for the semi-continuous cultures. A mixture of the five algae was used to inoculate one of two HRAPs for secondary treatment of TL. The other HRAP was filled with natural lake water containing mixed populations of algae. A volume of 400 mL (1%) from both ponds were removed daily and replaced with TL. The leachate loading rate was increased to 2% (0.8 L day−1) on day 197 and then to 4% (1.6 L day−1) on day 309, providing hydraulic retention time of 100, 50 and 25 days, respectively. Although higher biomass was obtained in the HRAP containing the consortium of five algae, there was no significant difference in reduction of pollutants between the two ponds. The HRAPs produced algal biomass ranging from 2.00 to 5.54 g dry weight L−1 with significant reduction in chemical oxygen demand (91.0%), ammoniacal nitrogen (99.9%) and orthophosphate (86.0%) contents. The HRAP offers a potential treatment system for TL which is simple, low cost, flexible in use and requiring low maintenance.

Bioremediation of Tannery Effluents Using a Consortium of Blue-Green Algal Species

Trivalent chromium in the form of basic chromium sulfate (BCS) is used for tanning hides/skins and is a strong pollutant of the soil and water bodies. Significant quantities of unutilized chemicals, such as sulfates, chlorides, are also discharged, contributing to high levels of total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), etc. Though many treatment techniques are being practiced, biotechnological methods are gaining importance. Biosorption is recognized as a cost-effective technology worldwide; one potential sorbent being blue–green algae (BGA), for treating metal-bearing effluents. This work studies the feasibility of using a species each of Spirulina, Oscillatoria, and Synechocystis, individually and as a consortium, as sorbents to remove Cr3+ from a segregated stream, viz. exhaust chrome liquor (ECL) and synthetic BCS solution. The species studied were found to be effective in removing Cr3+ considerably at varying concentrations, besides reducing sulfates, BOD, COD, etc. The results of ECL experiments were more encouraging than those for BCS solution. The kinetic data on Cr3+ sorption onto algal biomass fit well into the pseudo-second order model. The equilibrium data were analyzed using the classic Langmuir and Freundlich isotherm models, yielding good fits. The results of the experiments indicate that algal consortia could be good alternatives to the conventional treatment methods for leather and other industrial wastewaters containing chromium.

Biomass and bioenergy production potential of microalgae consortium in open and closed bioreactors using untreated carpet industry effluent as growth medium

Improved wastewater management with beneficial utilization will result in enhanced sustainability and enormous cost savings in industries. Algae cultivation systems viz. raceway ponds, vertical tank reactors (VTR) and polybags were evaluated for mass production of algal consortium using carpet industry (CI) untreated wastewater. Overall areal biomass productivity of polybags (21.1gm−2d−1) was the best followed by VTR (8.1gm−2d−1) and raceways (5.9gm−2d−1). An estimated biomass productivity of 51 and 77tonsha−1year−1 can be achieved using 20 and 30L capacity polybags, respectively with triple row arrangement. Biomass obtained from algal consortium was rich in proteins (∼53.8%) and low in carbohydrates (∼15.7%) and lipids (∼5.3%). Consortium cultivated in polybags has the potential to produce 12,128m3 of biomethane ha−1year−1. To be economically viable, the capital expenditure for polybag reactors needs to be reduced to $10m−2 for bioenergy/biofuel production.

Response of an Algal Consortium to Diesel under Varying Culture Conditions

A diesel-tolerant sessile freshwater algal consortium obtained from the vicinity of Powai Lake (Mumbai, India) was cultured in the laboratory. The presence of diesel in batch cultures enhanced the maximum specific growth rate of the algal consortium. With decrease in light-dark (L:D) cycle from 20:4 to 4:20 h, the chlorophyll-a levels decreased; however, the removal of diesel was found to be maximum at L:D of 18:6 h with 37.6% degradation over and above controls. In addition to growth in the form of green clumps, white floating biomass was found surrounding the diesel droplets on the surface. This culture predominated at the least L:D ratio of 4:20 h. Studies confirmed the ability of the floating organisms to grow heterotrophically in the dark utilizing diesel as carbon source and also in the presence of light in a medium devoid of organic carbon sources.

Growth of benthic freshwater algae on dairy manures

A potential alternative to land application of livestock manures for cropproduction is the production of algae to recover the nitrogen andphosphorus present in the manure. Compared to terrestrial plants,filamentous algae have exceedingly high growth and nutrient uptake rates. Moreover, they are capable of year-round growth in temperate climates,can be harvested on adapted farm-scale equipment, and yield a biomassthat should be valuable as an animal feed supplement. The objective of thisresearch was to evaluate algal turf scrubber (ATS) technology to removenitrogen, phosphorus and chemical oxygen demand from raw andanaerobically digested dairy manure. Laboratory-scale ATS units wereoperated by continuously recycling wastewater and adding manure effluentsdaily. ATS units were seeded with algal consortia from a nearby streamand grown using dairy manures from two different dairy farms. Algalbiomass was harvested weekly and dried prior to analysis for total Kjeldahlnitrogen, total phosphorus, and inorganic constituents. Wastewater sampleswere analyzed for total Kjeldahl nitrogen, ammonium, nitrate,orthophosphate, conductivity and chemical oxygen demand. Using atypical manure input containing 0.6–0.96 g total nitrogen day-1,the dried algal yield was approximately 5 g m-2 day-1. Thedried algae contained approximately 1.5–2% phosphorus and 5–7%nitrogen. Algal nitrogen and phosphorus accounted for 42–100% ofinput ammonium-nitrogen (33–42% of total nitrogen) and 58–100%of input total phosphorus, respectively.