Papers by rizwan muhammad
The co-culture system of photosynthetic micro-algae Chlorella vulgaris and aerobic heterotrophic ... more The co-culture system of photosynthetic micro-algae Chlorella vulgaris and aerobic heterotrophic bacteria Pseudomonas putida was investigated as a possible combination of symbiotic mixed culture for the simultaneous removal of nutrients (ammonium and phosphate) and organic contaminants. Using synthetic municipal wastewater, the co-culture system exhibited symbiotic enhancement in the removal of nutrients and organic carbon compared to each of axenic cultures. The co-culture system performed successfully in removing both of ammonium and chemical oxygen demand (COD), showing around 80% removal for 4 days. Strategies of nitrogen and phosphorous starvation in C. vulgaris for two days prior to main treatment did not increase the performance of nutrients removal, indicating that the nutrient starvation as a pretreatment is unnecessary. Without alkalinity (as bicarbonate), nutrients and COD were not removed significantly, implying that the existence of alkalinity is essential for symbiotic treatment of both nutrients and organics. Results demonstrated that co-culture system composed of C. vulgaris and P. putida can be a potential candidate of mixed culture system for the simultaneous removal of nutrients and organic carbon in wastewater treatment using a single reactor.
A B S T R A C T Simultaneous removal of nutrients (ammonium and phosphate) and COD was investigat... more A B S T R A C T Simultaneous removal of nutrients (ammonium and phosphate) and COD was investigated by the co-culture consortium of microalga Chlorella vulgaris and bacterium Pseudomonas putida. The co-culture system showed higher removal of both nutrients and COD than the each axenic culture, indicating that nutrients uptake capability of C. vulgaris was enhanced in the presence of P. putida. The best performance in the removal of nitrogen, phosphorus, and COD was obtained through the co-culture with suspended P. putida and immobilized C. vulgaris, demonstrating that the employment of immobilization of one species is more synergistic than suspended co-culture system in nutrients removal from wastewater.
Changes in the cell growth and lipid accumulation of marine microalga Dunaliella tertiolecta were... more Changes in the cell growth and lipid accumulation of marine microalga Dunaliella tertiolecta were investigated in response to the combination of different stress factors including the variation of iron supply as a primary stress factor and different options in light irradiation and CO2 supply as a secondary stress factor. High or limited Fe conditions could act as a stress for lipid synthesis. As a secondary stress factor, non-CO2 condition was good for lipid accumulation, but the overall cell growth was sacrificed significantly after a long-time cultivation. Dark condition as a secondary stress factor also favored lipid accumulation and the extent of cell density reduction at the early period in the dark was small compared to other stress conditions. The two-stage cultivation strategy was necessary to maximize lipid production because tendencies of the cell growth and lipid content were not identical under the chosen stress condition. The first stage was for preparing a high cell density under the normal growth-favoring condition and the second stage was the stress condition to induce lipid accumulation in a short time. The short-term (12 h) incubation under the 5X Fe (3.25 mg/L) and dark conditions resulted in the best lipid productivity of 1.44 g/L/d providing 2 g/L inoculum at the second stage.
A B S T R A C T Simultaneous removal of nutrients (ammonium and phosphate) and COD was investigat... more A B S T R A C T Simultaneous removal of nutrients (ammonium and phosphate) and COD was investigated by the co-culture consortium of microalga Chlorella vulgaris and bacterium Pseudomonas putida. The co-culture system showed higher removal of both nutrients and COD than the each axenic culture, indicating that nutrients uptake capability of C. vulgaris was enhanced in the presence of P. putida. The best performance in the removal of nitrogen, phosphorus, and COD was obtained through the co-culture with suspended P. putida and immobilized C. vulgaris, demonstrating that the employment of immobilization of one species is more synergistic than suspended co-culture system in nutrients removal from wastewater.
The effects of iron sources with different speciation and anionic moieties (ferric chloride, ferr... more The effects of iron sources with different speciation and anionic moieties (ferric chloride, ferrous chloride, ferric EDTA, ferrous EDTA, ferric ammonium sulfate, and ferrous ammonium sulfate) on the cell growth and the production of energy storage (lipid and carbohydrate) from Dunaliella tertiolecta were investigated. The influence of iron dosage was also compared in the range from 0.65 mg/L (1X) to 6.5 mg/L (10X) as Fe concentration. Best cell growth rate was achieved when ferrous ammonium sulfate was used. Ferric EDTA resulted in higher lipid content than other iron sources, while ferrous ammonium sulfate favored the accumulation of carbohydrate among six iron sources. The accumulations of lipid and carbohydrate as energy storage competed each other and thus both contents did not increase together. In the presence of ferric EDTA, lipid content is increasing, while carbohydrate content is decreasing. On the contrary, lipid content is decreasing while carbohydrate is increasing in the presence of ferric ammonium sulfate. Because the overall carbohydrate content was larger than that of lipid, bioethanol production would be more advantageous than biodiesel production with the present D. tertiolecta strain if the carbohydrate in D. tertiolecta contains a high fraction of glucose with a good saccharification yield.
A B S T R A C T Pakistan has a strong potential of biodiesel production if the available feedstoc... more A B S T R A C T Pakistan has a strong potential of biodiesel production if the available feedstock resources are used sustainably and implementable policies are made in appropriate direction. To meet the energy demands and to find alternative and non-conventional resources of energy different challenges like research and development, infrastructure development, decentralized type of power delivery system, commercialization, market development , education and outreach programs, public awareness, monitoring, subsidies, government participation, technology transfer and evaluation must be considered and a comprehensive policy must also be made to systematically control and integrate them at national level. Pakistan is enriched with a wide variety of feed stocks which can be used for biodiesel production. Pakistan has an enormous potential of biodiesel production from jatropha, plants seed oil and microalgae which needs more consideration and practical applications. Harvesting the potential of microalgae for biodiesel production in Pakistan can be helpful to make it self-sufficient for energy demands. Pakistan is also facing several challenges like climate change, lack of financial resources, state of art technology and absence of appropriate government policies, which limit the commercialization of biodiesel. Although Government of Pakistan has established different institutions to promote and develop alternative energy technologies and to achieve 10% share of bioenergy in the energy sector by 2020, but still the targets are to be achieved on practical grounds. In this article, we have reviewed the potential of biodiesel in Pakistan, feed stocks, biodiesel production process, barriers and future developments. Future policies on biofuels, trends, recommendations, and the implication of existing policies are also discussed with research and developments goals for the promotion of biodiesel in Pakistan.
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Papers by rizwan muhammad