Use Of Green Algae Research Articles

The Use of Green Algae to Capture Carbon Dioxide in Wastewater

The Use of Green Algae to Capture Carbon Dioxide in Wastewater

Biological treatment of agro-processing industrial effluents from tannery, coffee and dairy plants using green algae (<i>Chlorella Ssp</i>.) cultured in a photo bioreactor

Due to increased environmental pollution as a result of high emission rates from agro-processing industries, the effluents must be cleaned up before being released into the environment. This study outlines the use of green algae for nutrient removal from agro-processing effluents discharged from three agro-industries (namely coffee, dairy, and tannery) in Kenya and how they can be used for the propagation of microalgae for biofuel production. Green algae were grown inside a photobioreactor containing the three agro-industrial effluents as nutrient media for 21 days. Thereafter, the algae were harvested and evaluated for biofuel production. The effectiveness of green algae (chlorella ssp) to extract the cations from the various agro-processing effluents was used to gauge how well they performed. Additionally, the algae growth rate, quantity of lipids, and biomass generated were used to evaluate the strains' effectiveness in producing biofuel. The results indicate that the highest maximum algae growth rate of 14.528 mg/mL occurred in the dairy effluent. The corresponding values for the coffee and tannery effluents were 13.016 mg/mL and 10.866 mg/mL, respectively. Biochemical analysis was done to establish the amount of biomass in the algae. The results showed that there was higher biomass productivity per day of 293.944, 124.849, and 91.997 μg/mL for the dairy, coffee, and tannery effluents, respectively. The contents of linolenic acid in the chlorella strain in the dairy, coffee, and tannery effluents were 13.21, 12.86, and 15.98%, respectively. The values obtained were slightly above the recommended lower limit value of 12% (EN 14214, 2004) for the production of quality biofuels. The results further show that high chemical oxygen demand removal (maximum of 47.7–67.8%) and total phosphorus removal (maximum of 95%) were achieved in all three effluents. Finally, the fatty acid methyl ester profiles produced indicated that the lipid content of the cultivated green algae was appropriate for the production of biofuel.

Effect of Algae Decaying on Shrimp Culture System and Suggested Biological Remediation Strategies

Pond water with algae blooms was collected, and maintained in the dark over a 2-day period without nutritional supplements. The physico-chemical parameters and the density of algae were measured. The concentration of NH 4+-N, DIN and PO4–P in water in darkness significantly increased, and the density of algae decreased significantly. Isolated water was exposed to three bio-remediation water treatments: addition of green algae, Bacillus subtilis and photosynthetic bacteria. After remediation, the concentrations of NH4+ -N, NO3- -N, DIN and PO4- -P in the three treatment groups were significantly lower than the control group. No difference was observed in the concentration of NO2–N between the control group and the photosynthetic bacteria group. Results from all treatments showed water quality deterioration along with increase in nitrogen and phosphorus concentrations. Bio-remediation methods can be effectively adapted in shrimp culture after algae decay, and one of the most promising biological remediation strategies is the use of green algae.

Potential use of green algae as a biosorbent for hexavalent chromium removal from aqueous solutions.

The hexavalent chromium Cr(VI) poses a threat as a hazardous metal and its removal from aquatic environments through biosorption has gained attention as a viable technology of bioremediation. We evaluated the potential use of three green algae (Cladophora glomerata, Enteromorpha intestinalis and Microspora amoena) dry biomass as a biosorbent to remove Cr(VI) from aqueous solutions. The adsorption capacity of the biomass was determined using batch experiments. The adsorption capacity appeared to depend on the pH. The optimum pH with the acid-treated biomass for Cr(VI) biosorption was found to be 2.0 at a constant temperature, 45 °C. Among the three genera studied, C. glomerata recorded a maximum of 66.6% removal from the batch process using 1.0 g dried algal cells/100 ml aqueous solution containing an initial concentration of 20 mg/L chromium at 45 °C and pH 2.0 for 60 min of contact time. Langmuir and Freundlich isotherm equations fitted to the equilibrium data, Freundlich was the better model. Our study showed that C. glomerata dry biomass is a suitable candidate to remove Cr(VI) from aqueous solutions.

The adsorption potential and recovery of thallium using green micro-algae from eutrophic water sources

Thallium (Tl) is a highly volatile and toxic heavy metal regarded to cause pollution even at very low concentrations of several parts per million. Despite the extremely high risk of Tl in the environment, limited information on removal/recovery exists. The study focussed on the use of green algae to determine the sorption potential and recovery of Tl. From the study, removal efficiency was achieved at 100% for lower concentrations of ≥150mg/L of Tl. At higher concentrations in a range of 250–500mg/L, the performance of algae was still higher with sorption capacity (qmax) between 830 and 1000mg/g. Generally, Chlorella vulgaris was the best adsorbent with a high qmax and lower affinity of 1000mg/g and 1.11L/g, respectively. When compared to other studies on Tl adsorption, the tested algae showed a better qmax than most adsorbents. The kinetic studies showed better correlation co-efficient of ≤0.99 for Pseudo-second order model than the first order model. Recovery was achieved highest for C. vulgaris using nitric acid at 93.3%. The strongest functional groups responsible for Tl binding on the algal cell wall were carboxyl and phenols. Green algae from freshwater bodies showed significant potential for Tl removal/recovery from industrial wastewater.

Quantifying Uptake and Retention of Copper Ions in Silica-Encrusted Chlamydomonas reinhardtii

Using copper (II) ion as a model pollutant, we report a new bioremediation concept, which involves the use of green algae Chlamydomonas reinhardtii to efficiently collect copper ions from the solution, followed by encapsulating copper loaded algae with silica, thus reducing the bioavailability of copper ions in the solution. Specifically, the potential of Chlamydomonas reinhardtii as an active copper (II) absorbent was demonstrated by quantifying and characterizing the copper uptake rate, capacity, efficacy, as well as copper retention from C. reinhardtii. Subsequently, a method of encrusting copper loaded C. reinhardtii with silica was developed, taking the advantage that the presences of high abundant polysaccharides and glycoproteins on the cell walls, as well as the presence of (3-amino-propyl) trimethoxysilane (APS) can function as nucleation center for silicification process of tetramethyl orthosilicate (TMOS). Both fluorescence imaging and scanning electron microscope (SEM) imaging confirmed the silica encrustation. It is expected that silica encrustation of algae has the potential for in situ remediation of various contaminants in a wide range of environments while providing long-term stabilization and diminishing the bioavailability of the contaminants.

HAZARDOUS WASTE: Pond Algae Sequester Strontium-90

Strontium-90 is a radioactive by-product of fission reactions within nuclear reactors that generate electricity. About 3% of the mass of spent nuclear fuel consists of fission products including strontium-90.1 Because of its high decay energy and its long half-life of 30 years—it takes hundreds of years to decay naturally to harmless levels—strontium-90 is classified a high-level waste. Strontium-90 deposits in bone and bone marrow, and exposure from contaminated food and water is linked to bone cancer and leukemia.2 Now Derk Joester, an assistant professor of materials science and engineering at Northwestern University in Evanston, Illinois, and his colleagues have found that common freshwater green algae sequester strontium into insoluble crystals, offering a possible way to separate strontium-90 from less hazardous components of nuclear waste.3 Closterium moniliferum, a ubiquitous bright green pond alga, forms crystals composed of strontium, barium, and sulfate. The crescent-shaped algae store the crystals in tiny vacuoles. Barium is necessary for the organism to deposit strontium, and the Northwestern team found that varying the ratio of barium to strontium in water boosted the amount of strontium captured in crystals by a factor of up to 150.3 This enhanced the strontium selectivity of the process. Nonradioactive strontium was used for the proof-of-concept laboratory experiments. Whether C. moniliferum tolerates radioactive strontium-90 needs to be determined, but the authors point out these organisms “have proven to be resistant to harsh environments such as extreme temperature, acidic pH, low nutrient availability, and light limitation.”3 C. moniliferum also prefers strontium to calcium. This is important because calcium, a harmless mineral, is found in nuclear waste along with strontium. Plants tested for bioremediation do not differentiate between strontium and calcium, so they become saturated with the latter simply because it is more abundant.4 But C. moniliferum does differentiate: “Algae avoid this problem by actively excreting calcium during crystal formation,” Joester says. He adds that algae potentially could become direct bioremediation agents, and understanding how they lock up strontium could lead to better engineered microbes. The Northwestern team envisions a filtration system where algae would precipitate crystals in hours or days. The crystals would be harvested, then incinerated to remove organic matter. The remaining concentrated crystals would be fused into glass blocks (“vitrified”) for safe storage, according to first author Minna Krejci, a Ph.D. candidate at Northwestern University. Some nuclear waste is already vitrified,1 but Joester says the sheer volume of nuclear waste makes it economically unfeasible to contain everything in glass blocks. The U.S. Department of Energy estimates the cost to process all radioactive waste currently stored in the United States at $50 billion.5 “These results look very promising for the use of green algae for bioremediation,” says Belinda Sturm, an environmental engineer at the University of Kansas, Lawrence. However, algae grown for biofuels are expensive to harvest at large scale, and similar challenges may apply to algae that clean up nuclear waste. “This does not negate their potential but emphasizes the need for further study,” Sturm says. If sequestration proves successful, algae may help to recover strontium-90 dispersed in oceans, lakes, or rivers after nuclear accidents, such as leaks from the Fukushima nuclear power plant in Japan.6 Perhaps algae could be designed to sink to the bottom, allowing strontium-90 to decay without entering the food chain, or floating algae could be skimmed off the surface and contained, suggests Roger Blomquist, principal nuclear engineer at Argonne National Laboratory.

Growth of Nile tilapia (Oreochromis niloticus L.) fed with diets containing graded levels of green algae ulva meal (Ulva rigida) reared in geothermal waters of southern Tunisia

Summary The use of green algae ulva meal (UM) (Ulva rigida) was evaluated as a replacement for soybean meal in a practical diet formulated to contain 28% crude protein, 7.50% lipid and 15 kJ gross energy g−1. Soybean meal was replaced by 0%, 10%, 20% and 30% of UM (diets U0, U1, U2 and U3, respectively). The feeding experiment was carried out in an open circulation system. Each diet treatment was applied to triplicate groups of 30 fish (21.37 ± 0.193 g average wet weight) per tank (400 L) arranged in a completely randomized design. The fish were hand fed to satiation four times daily between 07.00 and 18.00 hours for 75 days. There were no significant differences (P > 0.05) in growth performance among fish fed with diets U0, U1 and U2. However, fish fed diet U3 had significantly lower growth (P < 0.05) than those fed diets U0, U1 and U2. Fish fed the control diet (U0) and diets including 10% and 20% UM had significantly (P < 0.05) better daily weight gain, relative growth weight, specific growth weight and protein efficiencies ratio than those fed with diet U3. Feed conversion ratio increased with increasing UM content, but only the value found in fish fed with diet U3 differed significantly (P < 0.05) from all other treatments. Survival rates ranged between 91.11% and 93.33%. No feed-related mortality was observed during the entire experimental period. Apparent protein digestibility (APD) of diets ranged from 87.06 to 69.91% and was lowest for fish fed with diet U3. In general, APD values decreased with increasing inclusion levels of UM, explained by the increase of anti-nutritional factors and high non-digestible fibre content. Compared to the control diet (U0), fish fed diets containing high levels of UM had lower levels of carcass lipid and higher levels of carcass moisture. Results show that this product can be included by up to 20% in practical male Nile tilapia diets with no detrimental effects.