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Microalgal biomass harvesting by inducing spontaneous flocculation (bioflocculation) sets an attractive approach, since neither chemicals nor energy are needed. Indeed, bioflocculation may be promoted by recycling part of the harvested microalgal biomass to the photobioreactor in order to increase the predominance of rapidly settling microalgae species. The aim of the present study was to improve the recovery of microalgal biomass produced in wastewater treatment high rate algal ponds (HRAPs) by recycling part of the harvested microalgal biomass. The recirculation of 2% and 10% (dry weight) of the HRAPs microalgal biomass was tested over one year in an experimental HRAP treating real urban wastewater. Results indicated that biomass recycling had a positive effect on the harvesting efficiency, obtaining higher biomass recovery in the HRAP with recycling (R-HRAP) (92-94%) than in the control HRAP without recycling (C-HRAP) (75-89%). Microalgal biomass production was similar in both systems, ranging between 3.3 and 25.8 g TSS/md, depending on the weather conditions. Concerning the microalgae species, Chlorella sp. was dominant overall the experimental period in both HRAPs (abundance>60%). However, when the recycling rate was increased to 10%, Chlorella sp. dominance decreased from 97.6 to 88.1%; while increasing the abundance of rapidly settling species such as Stigeoclonium sp. (16.8%, only present in the HRAP with biomass recycling) and diatoms (from 0.7 to 7.3%). Concerning the secondary treatment of the HRAPs, high removals of COD (80%) and N-NH (97%) were found in both HRAPs. Moreover, by increasing the biomass recovery in the R-HRAP the effluent total suspended solids (TSS) concentration was decreased to less than 35 mg/L, meeting effluent quality requirements for discharge. This study shows that microalgal biomass recycling (10% dry weight) increases biomass recovery up to 94% by selecting the most rapidly settling microalgae species without compromising the biomass production and improving the wastewater treatment in terms of TSS removal.

Airflow obstruction, dyspnea, lung hyperinflation and the lung extent of the bronchiectasis are four independent entities in the impact of bronchiectasis upon patients.

Aims: Proinflammatory cytokines are important mediators for the development of heart failure and increased plasma levels of these cytokines have been reported in patients with this condition. The purpose of the study was to investigate whether urine, a non-invasively obtained biological sample, was an appropriate medium in which to measure the concentration of tumor necrosis factor-alpha (TNF-a) and interleukin-6 (IL-6) in patients in the advanced stages of the disease. Methods and results: Thirty consecutive patients who had severe congestive heart failure (NYHA classes III and IV) and 30 matched healthy control subjects were enrolled. Plasma and the first urine of the day were collected and TNF-a and IL-6 were quantitatively analyzed by enzymelinked immunosorbent assays. For every subject there were no differences in the amount of cytokine determined in plasma and urine. Both urine and plasma levels of IL-6 and TNF-a were greater in heart failure patients than in controls. Conclusion: Our results show that plasmatic and urinary levels of proinflammatory cytokines did not differ significantly. Thus, urine may be a good milieu in which to study these cytokines and may have diagnostic, prognostic and therapeutic implications.

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