Microalgae bioreactor for nutrient removal and resource recovery from wastewater in the paradigm of circular economy.

Every day, large quantities of wastewater are discharged from various sources that could be reused. Wastewater contains nutrients such as nitrogen or phosphorus, which can be recovered. Microalgae-based technologies have attracted attention in this sector, as they are able to bioremediate wastewater, harnessing its nutrients and generating algal biomass useful for different downstream uses, as well as having other advantages. There are multiple species of microalgae capable of growing in wastewater, achieving nutrient removal efficiencies surpassing 70%. On the other hand, microalgae contain lipids that can be extracted for energy recovery in biodiesel. Currently, there are several methods of lipid extraction from microalgae. Other biofuels can also be obtained from microalgae biomass, such as bioethanol, biohydrogen or biogas. This review also provides information on bioenergy products and products in the agri-food industry as well as in the field of human health based on microalgae biomass within the concept of circular bioeconomy.

Influence of salinity cycles in bioreactor performance and microbial community structure of membrane-based tidal-like variable salinity wastewater treatment systems.

A membrane bioreactor and two hybrid moving bed bioreactor-membrane bioreactors were operated for the treatment of variable salinity wastewater, changing in cycles of 6-h wastewater base salinity and 6-h maximum salinity (4.5 and 8.5 mS cm-1 electric conductivity, which relate to 2.4 and 4.8 g L-1 NaCl, respectively), under different hydraulic retention times (6, 9.5, and 12 h) and total solids concentrations (2500 and 3500 mg L-1). The evaluation of the performance of the systems showed that COD removal performance was unaffected by salinity conditions, while BOD5 and TN removals were significantly higher in the low-salinity scenario. The microbial community structure showed differences with respect to salinity conditions for Eukarya, suggesting their higher sensitivity for salinity with respect to Prokarya, which were similar at both salinity scenarios. Nevertheless, the intra-OTU distribution of consistently represented OTUs of Eukarya and Prokarya was affected by the different salinity maximums. Multivariate redundancy analyses showed that several genera such as Amphiplicatus (0.01-5.90%), Parvibaculum (0.27-1.19%), Thiothrix (0.30-1.19%), Rhodanobacter (2.81-5.85%), Blastocatella (0.21-2.01%), and Nitrobacter (0.80-0.99%) were positively correlated with BOD5 and TN removal, and the ecological roles of these were proposed. All these genera were substantially more represented under low-salinity conditions (10-500% higher relative abundance), demonstrating that they might be of importance for the treatment of variable salinity wastewater. Evaluation of Eukarya OTUs showed that many of them lack a consistent taxonomic classification, which highlights the lack of knowledge of the diversity and ecological role of Eukaryotes in saline wastewater treatment processes. The results obtained will be of interest for future design and operation of salinity wastewater treatment systems particularly because little is known on the effect of variable salinity conditions in wastewater treatment.

GIS environmental information analysis of the Darro River basin as the key for the management and hydrological forest restoration.

This article presents analyses of soil and environmental information for the Darro River basin (Granada-Spain) preliminary to its hydrological and forestry restoration. These analyses were carried out using a geographical information system (GIS) and employing a new procedure that adapts hydrological forest-restoration methods. The complete analysis encompasses morphological conditions, soil and climate characteristics as well as vegetation and land use. The study investigates soil erosion in the basin by using Universal Soil Loss Equation (USLE) and by mapping erosion fragility units. The results are presented in a set of maps and their analysis, providing the starting point for river basin management and the hydrological and forestry-restoration project that was approved at the end of 2015. The presence of soft substrates (e.g. gravel and sand) indicates that the area is susceptible to erosion, particularly the areas that are dominated by human activity and have little soil protection. Finally, land use and vegetation cover were identified as key factors in the soil erosion in the basin. According to the results, river authorities have included several measures in the restoration project aimed at reducing the erosion and helping to recover the environmental value of this river basin and to include it in recreation possibilities for the community of Granada. The presented analytical approach, designed by the authors, would be useful as a tool for environmental restoration in other small Mediterranean river basins.

Kinetic modeling of Shewanella baltica KB30 growth on different substrates through respirometry.

BACKGROUND: Shewanella baltica KB30 was isolated from seawater collected in Kandalaksha Bay, White Sea (Russia). This strain is known for its ability to grow on a pool of different substrates, including carbohydrates, carboxylic and amino acids, and lipids. However, no data are available on its metabolic efficiency in relation to the use of different carbon sources typologies. This work represents the first attempt to characterize S. baltica by its heterotrophic kinetic performance. RESULTS: Growth and substrate consumption, during the biodegradation of sodium acetate, glucose, tween 80 and peptone, were analyzed through a respirometric method. To find the model best fitting the experimental data and to obtain the kinetic parameters, the equations of Monod, Moser, Contois and Tessier were applied. The kinetic behavior of S. baltica was fitted to Monod model for sodium acetate and tween 80, while it was adjusted to Contois model for glucose and peptone. In this regard, peptone was consumed faster than the other substrates, as indicated by the highest values of substrate degradation rate, which exceeded 60 mg O2 L-1 h-1. CONCLUSIONS: Proteolytic metabolism was favored than lipidic and glucidic metabolism, which could contribute much more to mineralization and recycling of proteins than lipids and carbohydrates.

Linkage of microbial kinetics and bacterial community structure of MBR and hybrid MBBR-MBR systems to treat salinity-amended urban wastewater.

Three pilot-scale bioreactors were started up and operated under salinity-amended urban wastewater feeding. The bioreactors were configured as membrane bioreactor and two different hybrid, moving bed biofilm reactor-membrane bioreactor and operated with a hydraulic retention time of 9.5 h, a solid residence time of 11.75 days and a total solids concentration of 2500 mg L-1 . The three systems showed excellent performance in suspended solids, BOD5 , and COD removal (values of 96-100%, 97-99%, and 88-90%, respectively), but poor nitrogen removal (values of 20-30%). The bacterial community structure during the start-up phase and the stabilization phase were different, as showed by ß-diversity analyses. The differences between aerobic and anoxic biomass-and between suspended and attached biomass-were higher at the start-up phase than at the stabilization phase. The start-up phase showed high abundances of Chiayiivirga (mean values around 3-12% relative abundance) and Luteimonas (5-8%), but in the stabilization phase, the domination belonged to Thermomonas (3-14%), Nitrobacter (3-7%), Ottowia (3-11.5%), and Comamonas (2-6%), among others. Multivariate redundancy analyses showed that Thermomonas and Nitrosomonas were positively correlated with fast autotrophic kinetics, while Caulobacter and Ottowia were positively correlated with fast heterotrophic kinetics. Nitrobacter, Rhodanobacter, and Comamonas were positively correlated with fast autotrophic and heterotrophic kinetics. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1483-1495, 2017.

Comparative analysis of the bacterial diversity in a lab-scale moving bed biofilm reactor (MBBR) applied to treat urban wastewater under different operational conditions.

Different types of carriers were tested as support material in a lab-scale moving bed biofilm reactor (MBBR) used to treat urban wastewater under three different conditions of hydraulic retention time (HRT) and carrier filling ratios (FR). The bacterial diversity developed on the biofilms responsible of the treatment was studied using a cultivation-independent approach based on the polymerase chain reaction-temperature gradient gel electrophoresis technique (PCR-TGGE). Cluster analysis of TGGE fingerprints showed significant differences of community structure dependent upon the different operational conditions applied. Redundancy analysis (RDA) was used to determine the relationship between the operational conditions (type of carrier, HRT, FR) and bacterial biofilm diversity, demonstrating a significant effect of FR=50%. Phylogenetic analysis of PCR-reamplified and sequenced TGGE bands revealed that the prevalent Bacteria populations in the biofilm were related to Betaproteobacteria (46%), Firmicutes (34%),Alphaproteobacteria (14%) and Gammaproteobacteria (9%).