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In this paper, the biomass and lutein productivity of the lutein-rich new strain Scenedesmus almeriensis is modelled versus irradiance and temperature. The results demonstrate that S. almeriensis is a mesophile microorganism with an optimal growth temperature of 35 degrees C, and capable of withstanding up to 48 degrees C, which caused culture death. This strain is also tolerant to high irradiances, showing no signs of photoinhibition even at the maximum irradiance essayed of 1625 microE m(-2) s(-1) accumulating up to 0.55% dry weight (d.wt.) of lutein. The optimal conditions that maximise the biomass productivity also favour the lutein productivity, lutein being a primary metabolite. Maximal biomass and lutein productivities of 0.87 g l(-1) day(-1) and 4.77 mg l(-1) day(-1), respectively, were measured. The analysis of light availability inside the cultures, quantified as average irradiance, demonstrates that the cultures were mainly photo-limited, although photosaturation also took place at high external irradiances. The effect of temperature was also investigated finding that the specific maximal growth rate is modified by the temperature according to the Arrhenius equation. The influence of both light availability and temperature was included in an overall growth model, which showed, as a result, capable of fitting the whole set of experimental data. An overall lutein accumulation rate model was also proposed and used in a regression analysis. Simulations performed using the proposed models show that under outdoor conditions a biomass productivity of 0.95 g l(-1) day(-1) can be expected, with a lutein productivity up to 5.31 mg l(-1) day(-1). These models may be useful to assist the design and operation optimisation of outdoor cultures of this strain.

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The use of ozone to disinfect sewage is becoming increasingly important, especially when a high degree of treatment is required. Ozone is a strong disinfectant with a high oxidation potential and is one of the most effective ways of inactivating pathogens. In order to observe and evaluate the effect of this disinfectant on the physical, chemical and microbiological characteristics of wastewaters, we analyzed the effluent input and output of an ozone disinfection plant located in Almeria, southeast Spain. The ozone input rate is adjusted according to the residual ozone content in the effluent output. The effluent is currently reused to irrigate vegetable crops. Another objective of this study has therefore been to verify the adequacy of this water treated process for preparing water for this purpose. Among the results obtained, it is important to highlight the fact that the ozone disinfection treatment was sufficient to inactivate faecal coliforms. We achieved reductions in these pathogens of around 89%. This treatment was respectful towards elements that give the reuse of effluent an added value in irrigation (N, P, K, etc) and also kept the quality of the waters within the authorized limits. Thus, we achieved up to 88% removal of COD, a maximum 68% removal of BOD 5 and up to 75% removal of suspended solids. Based on the results of the parameters analyzed in this ozonized effluent, we concluded that ozone-treated water is suitable for reuse in the irrigation of fresh consumption crops in accordance with the guidelines established in related legislation.

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