INTEGRATED SYSTEM FOR OPTIMIZED ALGAL PRODUCTION IN OPEN PONDSTarek Farouk Aly Fayed
AbstractABSTRACT Microalgae can metabolize various waste streams and convert the wastes into carbohydrates, lipids and proteins, which can be used to produce a wide variety of products. Lipids can be processed into biodiesel; carbohydrates into bioethanol and biomethanol; and proteins can be used as food supplement for humans and animal feedstock. Thus, microalgal cultivation can contribute to CO2 mitigation and nutrients recovery from wastewater and thus could be considered of high economic value. The present work aims to setup an integrated system which can optimize the microalgae productivity in open ponds along with reducing the capital cost needed to be commercially viable, through: 1-Enhancing the method of mixing of suspended algae to keep the algae cells always suspended next to the surface of the culture allowing the ability of increasing the depth of the algae pond without any increase in the power consumption, as well as the use of the economic paddlewheel method for mixing algal broth. Moreover increasing the depth of the algae pond leads to a decrease in the needed land area infrastructure. 2- Using captured CO2 released from incineration of agriculture residues (rice husk and corn stalk) in fluidized bed combustion, as a source of cheap carbon dioxide. 3- Using municipal wastewater ingredients (e.g., nitrogen and phosphorus) as a source of cheap macro nutrients. Results proved that microalgae cultivated in a 90 cm deep straight pond equipped with mobile electro-mechanical mixer, achieved the same growth rate, with lower power consumption than that cultivated in a traditional 30 cm deep raceway pond. Moreover, reductions in ammonia and dissolved phosphate concentrations in wastewater in a straight pond are approximately equal to that in a traditional raceway pond. Microalgae cultivated in a pond pumped with CO2 gas resulting from the incineration of agriculture residues (rice husk and corn stalk), achieved higher growth rate with lower hydraulic retention time than that cultivated without feeding carbon dioxide. The final result showed that the capital cost of algal production was reduced by about 30% as a result of reducing cost of mixing by about 25 % which represents over 10% from the total cost.
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