Mixed Algal Culture Research Articles

Biodeterioration potential of algae on building materials - Model study

Although biodeterioration of building materials is a well-recognized problem, unlike heterotrophic organisms the influence of aerophytic algae has been so far attributed only to aesthetical and indirect biodeterioration. This article concentrates on determining the influence of mixed algal cultures of Coenochloris signiensis, Stichococcus bacillaris, Klebsormidium flaccidum and Chlorococcum infusionum on brick and plaster samples, studied in model environment. Inoculated and incubated for 28 days samples were examined with chlorophyll a measurements, cell density estimation, microscopic observations, water absorptivity tests, pH determination and metabolome profiling. Algal growth led to the lowering pH values of plaster samples by 0.53–0.54 and brick samples by 0.29–0.36 as well as increasing water absorptivity by 4.65% and 4.76% respectively. CIE L*a*b color measurements revealed material discoloration of ΔE = 16.11 ± 1.38 for brick and ΔE = 16.59 ± 0.73 for plaster samples. Metabolome analysis confirmed high activity of biofilms with 112 metabolites detected on brick and 203 on plaster samples. 25 and 35 metabolic pathways were confirmed respectively. Compounds with documented biodeteriorative potential such as acetic, isobutyric and citric acid were found. The acquired results suggest that the impact of green algae on building substrates goes beyond aesthetic and indirect biodeterioration and should be further explored.

Detection and identification of a mixed cyanobacteria and microalgae culture using derivative spectrophotometry.

Early detection and monitoring of algal blooms and potentially toxic cyanobacteria in source waters are becoming increasingly important with rising climate change and industrialization. There is a growing need to measure the mixed microalgae cultures sensitively and accurately, as multiple algae species are present in natural source waters. This study investigated the detection of an equal concentration, mixed-culture of cyanobacteria (Microcystis aeruginosa) and a common green algae (Chlorella vulgaris) in water using UV-Vis spectrophotometry while employing longer pathlengths and derivative spectrophotometry to improve the detection limit. A strong linear relationship (R2>0.99) was found between the concentration and absorbance of the mixed-culture at 682nm using 50 and 100mm pathlengths. This study showed that the cyanobacterial (phycocyanin) peak could be separately identified in mixed-culture setting, while the chlorophyll peaks of both algae overlapped each other. The lowest detection limit of the mixed algal culture using traditional spectrophotometry and derivative spectrophotometry was calculated to be 25,997 cells/mL and 5505 cells/mL using a 100mm cuvette pathlength. Lastly, the performance of mixed-culture and individual algal cultures were compared, and analyses were carried out to evaluate differences in slopes which can be used for quantification purposes. The results indicate that derivative spectrophotometry significantly improved the detection limit making the method potentially viable for the early detection of mixed algal cultures.

Microalgae Potentials for Phycoremediation with Paint Effluent of Electroplating Industry

Water pollution is a one of the major environmental issue that the world is facing nowadays. The untreated effluent as well as the chemically treated effluent both results in pollutions. These toxic contaminants directly and indirectly affect the flora and fauna of the ecosystem. The solution for such a drastic environmental issue lies within the cells of one such cosmopolitan plant group namely “Algae”. These are certain algal species which have the inhibit capacity to utilize some of the most threatening environmental contaminants such as nitrogenous compounds, ammonia, phosphates and some of the metal ions so on. Hence, treating the effluent with algae would be an eco-friendly method to reduce pollution. Phycoremediation of effluent using algae is a novel green-technique when applied to aqueous pollution. The present investigation included the preliminary screening of microalgae potentials for their tolerance and growth in paint effluent from an electroplating industry which include the native microalgae isolated from the effluent treatment plant (ETP). The microalgae, such as Chlamydomonas pertusa, Dactylococcopsis raphioides and Chlorococcum humicolo were selected and employed in the treatment of electroplating paint effluent an individually and also as mixed algal group. The physico-chemical parameters were analyzed. The individual culture and the mixed algal culture both could effectively reduce TDS (Total Dissolved Solid), TSS (Total Suspended Solid), free ammonia, calcium, sodium, nitrate and phosphate. Chlorococcum humicolo had a significant remedial level of Turbidity (20.51%), Calcium (95.76%), Sodium (8.33%), Free ammonia (62.96%), Phosphate (71.29%) and Total Kjeldhal Nitrogen (48.23%) treated with paint effluent of electroplating industry among the microalgae. Thus, Chlorococcum humicolo could be selected for further field pilot scaling up study. Phycoremediation is a cost-effective, efficient and a sustainable technology for future clean earth.

Photosynthesis, competition, and wastewater treatment characteristics of the microalga Monoraphidium sp. Dek19 at cool temperatures

Monoraphidium sp. Dek19 (M. Dek19) is a versatile cold-adapted microalga suitable for treatment of municipal wastewater and production of biofuels from cellular lipids. This study investigated the growth and photosynthetic properties of M. Dek19 which allow it to phycoremediate effluent under cool conditions. Autotrophic cultures grown in tertiary effluent reached greater cell densities at 10 °C than at 22 °C. At both temperatures, this alga could completely deplete polluting PO43− and NO32− ions during growth to stationary phase. M. Dek19 also grew prolifically in primary effluent from an earlier water treatment stage. NH4+ was removed as an alternate N-source, and algal photosynthesis had potential for energy-saving oxygenation of downstream aerobic treatments, including the activated sludge step. In mixed algal culture at a cool temperature (10 °C), M. Dek19 outcompeted Chlorella sp. However, at 22 °C this advantage was diminished, and the population of M. Dek19 cells declined. Photosynthetic O2 evolution by log-phase M. Dek 19 cells at 22 °C showed light saturation at 100 μmol photons m−2 s−1. At 10 °C, photosynthetic rates were 50% lower, light saturation decreased to 60 μmol photons m−2 s−1, yet the cells grew to higher cell densities under cooler conditions. At stationary phase, maximal photosynthesis declined by 50%, indicating self-shading effects. Concurrently, cellular Chlorophyll (Chl) content increased 2-fold, and Chl a/b ratios increased from 1.7 to 3.72. This indicated an acclimation to lower light penetration as the culture matured. The potential for biofuel production was evident from the elevated neutral lipid content of M. Dek19 as nutrients were depleted from the wastewater. We conclude that M. Dek19 is well-adapted to low temperatures and light levels found in winter at many water treatment facilities in colder climates. Thus, M. Dek19 offers a means to phycoremediate municipal wastewater in geographical areas where outdoor growth of algae has previously been discounted as impractical.

Paraphysoderma sedebokerense Infection in Three Economically Valuable Microalgae: Host Preference Correlates with Parasite Fitness.

The blastocladialean fungus Paraphysoderma sedebokerense parasitizes three microalgae species of economic interest: Haematococcus pluvialis, Chromochloris zofingiensis and Scenedesmus dimorphus. For the first time, we characterized the developmental stages of isolated fungal propagules in H. pluvialis co-culture, finding a generation time of 16 h. We established a patho-system to compare the infection in the three different host species for 48 h, with two different setups to quantify parameters of the infection and parameters of the parasite fitness. The prevalence of the parasite in H. pluvialis and C. zofingiensis cultures was 100%, but only 20% in S. dimorphus culture. The infection of S. dimorphus not only reached lower prevalence but was also qualitatively different; the infection developed preferentially on senescent cells and more resting cysts were produced, being consistent with a reservoir host. In addition, we carried out cross infection experiments and the inoculation of a mixed algal culture containing the three microalgae, to determine the susceptibility of the host species and to investigate the preference of P. sedebokerense for these microalgae. The three tested microalgae showed different susceptibility to P. sedebokerense, which correlates with blastoclad’s preference to the host in the following order: H. pluvialis > C. zofingiensis > S. dimorphus.

Algal cells harvesting using cost-effective magnetic nano-particles

Innovative iron-based nanoparticles were synthesized, characterized and tested for the first time for harvesting single and mixed algal culture from real wastewater. The tailor-made magnetic nanoparticles (MNPs; Fe-MNP-I and Fe-MNP-II) achieved a percentage algae harvesting efficiency (%AHE) higher than 95% using a concentration of MNPs (CMNP) of 25 ± 0.3 (std. dev = 0.08) mg.L−1, mixing speed (Mspeed) of 120 ± 2 (std. dev = 0.10) rpm, short contact time (Ct) of 7 ± 0.1 (std. dev = 0.05) min and separation time (SPt) of 3 ± 0.1 (std. dev = 0.09) min. The optimum operational conditions for harvesting of Chlorella vulgaris (C.v) were determined at (CMNP = 40 ± 0.4 (std. dev = 0.5) gMNPs.L−1, SPt = 2.5 ± 0.4 (std. dev = 0.1) min, Mspeed = 145 ± 3 (std. dev = 1.50) rpm and Ct = 5 ± 0.3 (std. dev = 0.10) min using surface response methodology. Langmuir model describes better the adsorption behavior of algae-Fe-MNP-I system, while both Langmuir and Freundlich fit well the adsorption behavior of algae-Fe-MNP-II. The maximum adsorption capacity of Spirulina platensis (SP.PL) (18.27 ± 0.07 (std. dev = 0.19) mgDWC.mgparticles−1) was higher than that for Chlorella vulgaris (C.v) (11.52 ± 0.01 (std. dev = 0.34) mgDWC.mgparticles−1) and mixed algal culture (M.X) (17.20 ± 0.07 (std. dev = 0.54) mgDWC.mgparticles−1) over Fe-MNP-I. Zeta potential measurements revealed that the adsorption mechanism between MNPs and algal strains is controlled by electrostatic interaction. The synthesized MNPs were recycled 10 times using alkaline-ultrasonic regeneration procedure.

Characterization of Soluble Algal Products (SAPs) after electrocoagulation of a mixed algal culture

The dewatering of algal culture requires coagulation of the algal cells. However, the coagulation in a continuous operation is slowed down through the excretion of Soluble Algal Products (SAPs). Electrocoagulation (EC), already utilized as a coagulation technique, has been investigated for its effects on SAPs characterizations. A mixed culture of Chlorella vulgaris, Scenedesmus Obliquus, Botryococcus braunii, Botryococcus sudeticus, and Afrocarpus falcatus was prepared and SAPs characteristics, including Specific Ultra Violet Absorbance (SUVA), Zeta potential, Molecular Weight (MW) fractionation, Dissolved Organic Carbon (DOC), protein and carbohydrate content, Excitation-Emission Matrix, and hydrophobicity using XAD resins, were measured and evaluated before and after electrocoagulation using mild steel and aluminum electrodes at 5 and 10 min. The results showed several improvements after EC. According to results, EC can render SAPs hydrophobicity up to 95 %, and the fluorescence peak results showed the complete removal of humic-like. Moreover, the SAPs were removed up to 21, 60, and 47 % for protein, carbohydrate and DOC, respectively. Results collectively showed that electrocoagulation might be able to mitigate the negative effects of growth on flocculation.

Bio-treatment of wastewater using mixed algal cultures

This study was carried out to evaluate the efficiency of mixed algal cultures for wastewater treatment. Free and alginate-immobilized forms of mixed algal culture were used. The highest removal percentages of biological oxygen demand (BOD) were 86.4% and 71.2 % after 32hrs and 48 hrs. in case of free and immobilized cells, respectively. Moreover, the highest values of chemical oxygen demand (COD) removal were 83.74% and 59.71% after 32hrs and 48 hrs for free and immobilized cells, respectively. Treatment with free cells showed removal values for total dissolved salts (TDS), phosphorus and NH3-N were 20.5%, 34.6% and 43.8% respectively after 32 hours. While in case of immobilized cells the highest removal values 18.4%, 34% and 58.5%, for TDS, Phosphorus and NH3-N, respectively were recorded after 48 hrs. Generally, concentration of heavy metals decreased due to treatment with algal free and immobilized cells. As a result of treatment with algal free and immobilized cells, 100% and 95.9% of Cu wastewater content was removed after 8 hrs and 48 hrs, respectively. Moreover, 96.2% and 98.1% of Fe was removed after 32 and 48 hours due to application of free and immobilized cells, respectively. As a result of inoculation with the mixed algal cultures in free cells 99.4% of Mn and 84.2% of Zn content were removed after 32 hours. Whereas, 98.6% of Pb content was removed after only 8 hrs. In case of using the immobilized cells the highest removal percentages of the three heavy metals recorded after 48 hours as follow 97.8% of Mn, 89.0% of Pb and 97.37% of Zn. Accordingly, treatment of wastewater with mixed algal free or immobilized cells is a fruitful method to produce an effluent of high quality to be used for irrigation. Whereas, the algal free cells were found to be more efficient than the immobilized ones.

Productivity of the mixed culture of microalgae Desmodesmus armatus (Chod.) Hegew. and Acutodesmus dimorphus (Turpin) Tsarenko

The article is devoted to the study of the productivity of mixed cultures of microalgae Desmodesmus armatus (Chod.) Hegew. and Acutodesmus dimorphus (Turpin) Tsarenko. Algae were mixed in the following ratios: D/A (1:1), D/A (1:2) and D/A (2:1). The efficiency of mixed cultures growing was compared with that for monocultures of D. armatus and A. dimorphus. Mono- and mixed cultures of algae were grown in Tamiya for 21 days, in a climatic room. Every three days, the amount of biomass was analyzed according to the density of the culture. By the end of the stationary growth phase, the biomass productivity of mono- and mixed algal cultures was analyzed. It was noted that the largest amount of biomass accumulates in the mixed D/A culture (1:1) on the 12th day of cultivation. The nutrient content in the mixed cultures biomass depends on cultivation conditions and does not significantly differ from that for monocultures of both species. The highest amount of total protein was observed in the mixed D/A culture (1:1). The content of chlorophyll a and b differs slightly in the three variants of mixed cultures and is at the level of the monoculture indicator. The content of carotenoids conclusively decreased in 1.6 - 1.8 times in mixed cultures as compared to monocultures. The biomass of a mixed culture of D. armatus and A. dimorphus in a 1: 1 ratio can be used to grow the freshwater zooplankton.

Intergraded wastewater treatment and carbon bio-fixation from flue gases using Spirulina platensis and mixed algal culture

In this work, Spirulina platensis (SP.PL) and mixed algal culture (M.X) were used as an economical treatment technology to solve dual environmental issues related to carbon dioxide (CO2) capturing and wastewater treatment. The impact of the concentration of CO2 (2.5%, 5%, 10%, and 15% v/v) on the specific growth rate (μ) of SP.PL and M.X, biomass production (Px), carbon dioxide bio-fixation rate (RCO2), organic matters and nutrient removals were assessed. The μ values of SP.PL and M.X increased by increasing the CO2 concentration until the optimum value (10v/v%) was reached, after that, increasing the CO2 dose negatively affected the growth rate. μ values ranged from 0.45–0.79 day−1 for SP. PL and from 0.48 to 0.86 day-1 for M.X. Both algae strains have shown high biomass productivities (Px of 0.246 gdw.L−1.d−1 for SP.PL and 0.384 gdw.L−1.d−1 for M.X), and significant carbon bio-fixation rates (RCO2 of 0.360 gC.L−1.d−1 for SP.PL and 0.460 gC.L−1.d−1 for M.M). the M.X obtained from the secondary basin of local WWTP performed better than single strain SP.PL in removing organic matter (% CODremoval ˜ 97.2), total inorganic nitrogen (% TINremoval ˜ 99.6) and total phosphorus (TPremoval˜ 99.41) under all studied conditions. Microalgae with fast growth rate and naturally grown in the water system can be a sustainable and effective technology for CO2 uptake and nutrients removals.

Monoalgal and mixed algal cultures discrimination by using an artificial neural network

In this paper, a rapid methodology to elucidate microalgae species in suspensions has been developed and validated. To do this, microalgae spectral signatures from light absorption measurements of different algal species were analysed through an artificial neural network (ANN) in order to describe and classify them. Four important species were used: Nostoc sp., Scenedesmus almeriensis, Spirulina platensis and Chorella vulgaris. Absorbance from monoalgal and mixed algal cultures was the input data for training, testing and validating the ANN. The results show that the ANN was capable of distinguishing between monoalgal and mixed algal cultures, identifying the microalgae species in the monoalgal cultures and providing the approximate composition of mixed algal cultures. These results confirm that the application of spectral signatures with ANN is a suitable method for approximating the biological composition of microalgae cultures.

PRODUCTIVITY OF THE MIXED CULTURE OF MICROALGAE DESMODESMUS ARMATUS (CHOD.) HEGEW. AND ACUTODESMUS DIMORPHUS (TURPIN) TSARENKO

Стаття присвячена вивченню продуктивності змішаних культур мікроводоротей Desmodesmus armatus (Chod.) Hegew. та Acutodesmus dimorphus (Turpin) Tsarenko. Водорості змішували у наступних піввідношеннях: D/А (1:1), D/А (1:2) та D/А (2:1). Ефективність вирощування змішаних культур порівнювали із такою для монокультур D. armatus та A. dimorphus. Моно- та змішані культури водоростей вирощували на середовищі Тамія протягом 21 доби, в умовах кліматичної кімнати. Кожні три доби аналізували кількість біомаси за показником густини культури. На кінець стаціонарної фази росту аналізували продуктивність біомаси монота змішаних культур. Відмічено, що найбільша кількість біомаси накопичується у змішаній культурі D/А (1:1) на 12 добу культивування. Вміст нутрієнтів у біомасі змішаних культур залежить від умов культивування і значно не відрізняється від такого для монокультур обох видів. Найбільша кількість загального білка відзначено у змішаній культурі D/А (1:1). Вміст хлорофілів а та b незначно відрізняється у трьох варіантів змішаних культур та знаходиться на рівні показника монокультр. Вміст каротиноїдів достовірно зменшився у змішаних культурах порівняно з монокультурами у 1,6 – 1,8 рази. Біомасу змішаної культури D. armatus та А. dimorphus у співвідношенні 1:1 можна використовувати для вигодовування прісноводного зоопланктону.

Integrated utilization of microalgae cultured in aquaculture wastewater: wastewater treatment and production of valuable fatty acids and tocopherols

Microalgal cultivation in aquaculture wastewater (AWW) from recirculating aquaculture systems (RAS) is an approach for combined production of valuable algal biomass and AWW treatment. The growth, nutrient uptake, fatty acid (FA) profile, and tocopherol content of mixed algal cultures of Euglena gracilis with Selenastrum grown in AWWs from pikeperch (Sander lucioperca) and catfish (Clarias anguillaris) RAS were studied. The highest algal biomass (1.5 g L−1), lipid (84.9 mg L−1), and tocopherol (877.2 μg L−1) yields were achieved in sludge-amended pike perch AWW. Nutrient removal rates in experiments were 98.9–99.5 and 98.4–99.8% for NH4-N and PO4-P, and 75.4–89.2% and 84.3–95.7% for TN and TP, respectively, whereas the COD was reduced by 45.8–67.6%. Biomass EPA and DHA content met, while ARA and tocopherol content exceeded the requirements for fish feed. Algal cultivation in AWWs is a promising alternative for AWW treatment while providing a replacement for fish oil in feed.

Conversion of biowaste leachate to valuable biomass and lipids in mixed cultures of Euglena gracilis and chlorophytes

Microalgae are a sustainable alternative for production of valuable omega −3 fatty acids (FAs), but high production costs limit commercialization. Utilization of waste as a nutrient source increases the economics of the cultivation process. Additionally, using mixed algal cultures instead of monocultures makes the cultivation process more flexible and can increase biomass and lipid production. Here, the growth and lipid production of microalgae Euglena gracilis, Selenastrum sp. and, Chlorella sorokiniana were studied in mono- and mixed cultures in small and pilot scale experiments in biowaste leachate. In pilot scale, also nutrient reduction and the number of bacteria were analyzed. Biomass production in the most productive mixed cultures was similar, but not higher than in most productive monocultures. The lipid production was highest in the small-scale monoculture of Selenastrum (10.4% DW) and in the pilot scale culture of Selenastrum with E. gracilis (11.1% DW). The content of alpha-linolenic acid (ALA) increased and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) remained stable during the cultivation period in all pilot scale cultures. However, increases in biomass and lipid production toward the end of the cultivation resulted in higher EPA and DHA yields in the well growing monoculture of E. gracilis and in the mixed culture of E. gracilis with Selenastrum. Co-cultivation of E. gracilis and Selenastrum also had a positive influence on nutrient uptake and resistance against bacteria. This type of mixed culture may be a good option for commercialization. However, as shown here, minor changes in cultivation conditions can rapidly result in dominance of a subdominant strain, and thus the stability of strain performance and production of desired FAs needs further investigation.

Mixed culture of Chlorella sp. and wastewater wild algae for enhanced biomass and lipid accumulation in artificial wastewater medium

The purpose of this work is to study the co-cultivation of Chlorella sp. and wastewater wild algae under different cultivation conditions (i.e. CO2, light intensity, cultivation time, and inoculation ratio) for enhanced algal biomass and lipid productivity in wastewater medium using Response Surface Methodology (RSM). The results show that mixed cultures of Chlorella sp. and wastewater wild algae increase biomass and lipid yield. Additionally, findings indicate that CO2, light intensity and cultivation time significantly affect algal productivity. Furthermore, CO2 concentration and light intensity, and CO2 concentration and algal composition, have an interactive effect on biomass productivity. Under different cultivation conditions, the response of algal biomass, cell count, and lipid productivity ranges from 2.5 to 10.2 mg/mL, 1.1 × 106 to 8.2 × 108 cells/mL, and 1.1 × 1012 to 6.8 × 1012 total fluorescent units/mL, respectively. The optimum conditions for simultaneous biomass and lipid accumulation are 3.6% of CO2 (v/v), 160 µmol/m2/s of light intensity, 1.6/2.4 of inoculation ratio (wastewater-algae/Chlorella), and 8.3 days of cultivation time. The optimal productivity is 9.8 (g/L) for dry biomass, 8.6 E + 08 (cells/mL) for cell count, and 6.8 E + 12 (Total FL units per mL) for lipid yield, achieving up to four times, eight times, and seven times higher productivity compared to nonoptimized conditions. Provided is a supportive methodology to improve mixed algal culture for bioenergy feedstock generation and to optimize cultivation conditions in complex wastewater environments. This work is an important step forward in the development of sustainable large-scale algae cultivation for cost-efficient generation of biofuel.

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.

Chlorophytes prolong mixotrophic Ochromonas eliminating Microcystis: Temperature-dependent effect

Cyanobacterial blooms, caused by eutrophication and climate warming, exert severely negative effects on aquatic ecosystem. Some species of protozoans can graze on toxic cyanobacteria and degrade microcystins highly efficiently, which shows a promising way to control the harmful algae. However, in the field, many different species of algae coexist with Microcystis and may affect protozoans eliminating Microcystis. Therefore, in this study, we assessed the impacts of chlorophytes, a type of beneficial algae for zooplankton and common competitors of cyanobacteria, on flagellate Ochromonas eliminating toxin-producing Microcystis at different temperatures. Our results showed that Ochromonas still eliminated Microcystis population and degraded the total microcystins with the addition of chlorophytes, although the time of eliminating Microcystis was prolonged and temperature-dependent. Additionally, in the grazing treatments, chlorophytes populations gradually increased with the depletion of Microcystis, whereas Microcystis dominated in the mixed algal cultures without Ochromonas. The findings indicated that although chlorophytes prolong mixotrophic Ochromonas eliminating Microcystis, the flagellate grazing Microcystis helps chlorophytes dominating in the primary producers, which is significant in improving water quality and reducing aquatic ecosystem risks.

Potential of Mixed Algal Culture for Lipid Synthesis using Wastewater as a Nutrient Source

Microalgae can be a good alternative source for wastewater treatment and lipid production owing to their ecofriendly photosynthetic approach. A comparative study was conducted between synthetic media and wastewater in which mixed algal culture (Scenedesmus obliquus, Chlamydomonas reinhardtii and Chlorella vulgaris) was grown. In this study, the growth of mixed algal culture and total lipid contents were analysed. Removal efficiency of nitrate, phosphate and chemical oxygen demand (COD) of mixed algal culture using wastewater as medium was found to be 68.1%, 84.36% and 78%, respectively, and for heavy metals like Zn, Pb, Fe, Cr and Cu, it ranged between 91% and 98%. The lipid content of mixed algal culture was observed to be 7.04%, 10.37% and 16.96% dcw in both synthetic media (BG-11 and BBM) and wastewater. Hence, it can be concluded from this study that synthetic media can be replaced by wastewater for growing mixed algal culture, which in turn can be used for biodiesel production.

Evaluating the usability of 19 effluents for heterotrophic cultivation of microalgal consortia as biodiesel feedstock

A key reason inhibiting commercialization of algal oil as biodiesel feedstock, is cultivation cost. For this reason, the usability of 19 readily available industrial effluents (autoclaved and non-autoclaved) to support heterotrophic growth and lipid accumulation was evaluated using six mixed algal cultures. Autoclaved whey effluent was the best with 14.32 g biomass L−1, 13.23% lipids, resulting in a lipid production of 1.91 g lipids L−1. Biomass production and lipid accumulation were in many cases inverse, e.g. mixed algal culture termed TUT4 accumulating 84.25% lipids on autoclaved acid mine drainage, with very little biomass produced. Biomass production was dependent on the effluent type, whereas the lipid accumulation was influenced mostly by the specific mixed algal cultures. The fatty acid composition of the algal oil (fish cannery and whey effluents) showed high saturation, leading to acceptable cetane numbers, kinematic viscosity, good oxidative stability, but poor cold flow properties.

200 kHz Sonication of Mixed-Algae Suspension from a Eutrophic Lake: The Effect on the Caution vs. Outbreak Bloom Alert Levels

For effective ultrasonic algae removal, several studies have considered the ultrasound equipment linked factors, such as power and frequency. However, studies on the response of mixed algal cultures and associated water quality parameters to ultrasound are limited. In this lab-scale sonication, the removal of cyanobacteria at a pre-set frequency of 200 kHz on mixed algae suspensions collected from a eutrophic lake was investigated. The caution (17.5 µg/L) and outbreak (1450 µg/L) alert levels in terms of chlorophyll-a (Chl-a) concentrations of the initial samples were each sonicated for 10, 15, and 20 min, and then kept in an incubator. Fifteen minutes of sonication resulted in best removal efficiency of 0.94 and 0.77, at an ultrasonic dose of 30 kWh/m3 at the outbreak and caution level concentrations, respectively. Immediately after 15 min sonication, and after standing in the incubator for a day, chlorophyll-a removal efficiencies of 0.28 and 0.90 were achieved in the outbreak level, respectively, and the matching removal efficiencies for the caution level were 0.23 and 0.64. Even though the removal was substantial in both cases, the final 147 µg/L chlorophyll-a concentration of the outbreak, which is itself still in the outbreak level range, shows that ultrasonication is not effective to satisfactorily remove algae from a concentrated suspension. Total dissolved nitrogen and chemical oxygen demand were reduced, overall, due to sonication. However, total dissolved phosphorus of the concentrated level was increased during the treatment. Although sonication needs further replicated experimental testing in whole-lake systems, our results show that 200 kHz sonication was able to reduce chlorophyll-a concentrations in small-scale laboratory tests.