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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. i.e. carbon, nitrogen and phosphorus; however other nutrients are also reviewed. M A N U S C R I P T A C C E P T E D 21Nutrients are generally taken up in the inorganic form, but several organic forms of 22 them are also assimilable. Some nutrients do not display any inhibition effect on believed that they will play a significant role in the sector of renewable energy nutrients for the production of microalgae using either synthetic fertilizers or 83 wastewater streams. The review will focus and discuss not only issues related to the 84 physiology of microalgae/cyanobacteria but also will discuss technical concerns 85 about the application of nutrients for biomass production. The main focus will be on 86 the nutrients carbon, nitrogen and phosphorus; however the minor nutrients 87 potassium, magnesium, sulfur and calcium will also be reviewed. CO2 is dissolved in water it reacts with the water molecules (H2O) and forms a weak104 acid-base buffer system, having the following equilibrium ( Fig Fig Fig Figure ure The above equilibrium depends on the pH of the solution, which means that 110 the relative amount of the dissolved inorganic carbon (DIC) species is strictly 111 related to the pH of the solution. Based on the equilibrium of the carbon species 112( Fig Fig Fig Figure ure Inorganic carbon is fixed inside the microalgal cells and is converted to 129Since the form and the amount of dissolved inorganic carbon depends on pH, 130 salinity, pressure and temperature ( Fig Fig Fig Figure ure 147The form of inorganic carbon utilization depends also on its concentration in the 148 medium; in high DIC concentration it seems that CO2 is preferred over HCO3 - 149(Aizawa and Miyachi 1986). It was shown that the active uptake of CO2 is 150 significantly faster than that of HCO3 - (Matsuda et al. 1999)

Microalgal biomass seems to be a promising feedstock for biofuel generation. Microalgae have relative high photosynthetic efficiencies, high growth rates, and some species can thrive in brackish water or seawater and wastewater from the food- and agro-industrial sector. Today, the main interest in research is the cultivation of microalgae for lipids production to generate biodiesel. However, there are several other biological or thermochemical conversion technologies, in which microalgal biomass could be used as substrate. However, the high protein content or the low carbohydrate content of the majority of the microalgal species might be a constraint for their possible use in these technologies. Moreover, in the majority of biomass conversion technologies, carbohydrates are the main substrate for production of biofuels. Nevertheless, microalgae biomass composition could be manipulated by several cultivation techniques, such as nutrient starvation or other stressed environmental conditions, which cause the microalgae to accumulate carbohydrates. This paper attempts to give a general overview of techniques that can be used for increasing the microalgal biomass carbohydrate content. In addition, biomass conversion technologies, related to the conversion of carbohydrates into biofuels are discussed.

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Phosphorus (P) recovery from wastewater is of great interest especially when the loaded adsorbent can be used in the agriculture as slow-release fertilizer. The application depends on environmental concerns related to the chemical modification of the adsorbent and the release of toxic compounds from the loaded material to the soil or the water during adsorption. The present work focused on the phosphate (PO4-P) removal from aqueous solutions under low P concentrations (0.5-10 mg/L) by using Ca(OH)2-pretreated natural zeolite (CaT-Z). As activation agent, Ca(OH)2 presents benefits in terms of pretreatment costs and environmental impact of the applied adsorbent. The pretreatment of natural zeolite (clinoptilolite) with 0.25 mol/L Ca(OH)2 led to an increase of P removal from 1.7 to 97.6% at initial P concentration of 10 mg/L, pH 7 and 298 K. A significant reduction of the soluble reactive P was achieved with low residual concentrations of 81-238 μg P/L at 298 K rendering CaT-Z a promising sorbent for tertiary wastewater treatment. At 200 mg P/L, the adsorption capacity was 7.57 mg P/g CaT-Z. The P removal efficiency was pHindependent suggesting a beneficial use of CaT-Z under acidic and alkaline conditions. Adsorption was found to be an endothermic and slow process reaching equilibrium after 120 h, whereas the half of the PO4-P was adsorbed in the first 8 h. The applied kinetic models showed that both film and intraparticle diffusion contributed to phosphate removal. Phosphate sorption decreased in the presence of the anionic surfactant SDS, Fe 2+ , HCO3-, acetate and citrate anion. The predominant mechanisms of ligand exchange and CaP surface precipitation were confirmed by the IR-ATR and SEM-EDS analyses, respectively.