Bioreactor for microalgal cultivation systems: strategy and development

Microalgae are important natural resources that can provide food, medicine, energy and various bioproducts for nutraceutical, cosmeceutical and aquaculture industries. Their production rates are superior compared to those of terrestrial crops. However, microalgae biomass production on a large scale is still a challenging problem in terms of economic and ecological viability. Microalgal cultivation system should be designed to maximize production with the least cost. Energy efficient approaches of using light, dynamic mixing to maximize use of carbon dioxide (CO2) and nutrients and selection of highly productive species are the main considerations in designing an efficient photobioreactor. In general, optimized culture conditions and biological responses are the two overarching attributes to be considered for photobioreactor design strategies. Thus, fundamental aspects of microalgae growth, such as availability of suitable light, CO2 and nutrients to each growing cell, suitable environmental parameters (including temperature and pH) and efficient removal of oxygen which otherwise would negatively impact the algal growth, should be integrated into the photobioreactor design and function. Innovations should be strategized to fully exploit the wastewaters, flue-gas, waves or solar energy to drive large outdoor microalgae cultivation systems. Cultured species should be carefully selected to match the most suitable growth parameters in different reactor systems. Factors that would decrease production such as photoinhibition, self-shading and phosphate flocculation should be nullified using appropriate technical approaches such as flashing light innovation, selective light spectrum, light-CO2 synergy and mixing dynamics. Use of predictive mathematical modelling and adoption of new technologies in novel photobioreactor design will not only increase the photosynthetic and growth rates but will also enhance the quality of microalgae composition. Optimizing the use of natural resources and industrial wastes that would otherwise harm the environment should be given emphasis in strategizing the photobioreactor mass production. To date, more research and innovation are needed since scalability and economics of microalgae cultivation using photobioreactors remain the challenges to be overcome for large-scale microalgae production

Occurence of inter-eruption debris flow and hyperconcentrated flood-flow deposits on Vesuvio Vulcano

In the period between AD 79 and AD 472 eruptions, inter-eruption debris ¯ow and hyperconcentrated-¯ood-¯ow deposits were deposited in the Somma-Vesuvio areas. These deposits, forming cliffs at the Torre Bassano and Torre Annunziata, were generated by highly erosive ¯oods, whose erosive capacity was enhanced by acceleration due to the steepness of the volcano slopes. In this type of deposits were distinguished ®ve depositional facies (from A to E) outcropping well at Torre Bassano where they are stacked in three ®ning-upward (FU) sequences, probably representing three forestepping ‹ backstepping episodes in the emplacement area of gravity ¯ows. These ®ve facies from coarse to ®ne are interpreted to represent the downcurrent evolution of particular composite sediment gravity ¯ows characterized by horizontal segregation of the main grain-size population. The blocking of these highly concentrated composite parent ¯ows would ®rst produce the deposition of the coarse front part to form facies A and then the overriding of this deposit by the bipartite ¯ow, which constitutes the body of the ¯ow. This ¯ow is composed of a highly concentrated basal inertia carpet responsible for the deposition of facies B, C and D and an upper hyperconcentrated ¯ood ¯ow that forms facies E, through traction plus fallout processes, respectively. Finally, the occurrence of ªlaharº type events at Somma-Vesuvio region even at present times is discussed. q 2001 Elsevier Science B.V. All rights reserved