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Blanco S.,The Institute of the Environment | Romo S.,University of Valencia | Cejudo-Figueiras C.,The Institute of the Environment | Goma J.,University of Barcelona | And 2 more authors.
Wetlands | Year: 2016

Increased nutrient loading is regarded as one of the major causes of a shift from macrophyte to phytoplankton dominance in shallow lakes. This work investigates the responses of phytoplankton and epiphyton biomass, macrophytes and algal species assemblages along a trophic gradient in some shallow Mediterranean lakes. A unimodal response of epiphyton biomass to increasing phosphorus levels was observed, while phytoplankton developed exponentially and submerged aquatic plant coverage decreased. At TP levels above 100 μg L−1 (~30 μg-P L−1 by element) phytoplankton began to dominate over the other primary producers and led the system to a turbid state, mainly dominated by cyanobacteria. This could be regarded as a critical threshold to avoid algal turbid states, especially for shallow Mediterranean lakes. Macrophyte typology was also important in modulating this response. On average, the unimodal maximum of epiphyton biomass was about 20 μg g−1 of macrophyte dry weight and hydrophytes had higher epiphytic biomass than helophytes. The coverage of submerged aquatic vegetation was not related to the epiphytic and phytoplanktonic biomass, but to the distribution of their species. Further studies on epiphyton-plant ecology are needed, especially for specific aquatic macrophyte conservation and lake management. © 2016 Society of Wetland Scientists


Kahlert M.,Swedish University of Agricultural Sciences | Acs E.,Danube Research Institute | Almeida S.F.P.,University of Aveiro | Blanco S.,University of León | And 9 more authors.
Hydrobiologia | Year: 2016

Investigations on organism ecology, biodiversity and biogeography often use large compiled datasets to extract information on species ecological preferences, which then can be used in environmental assessment. Freshwater benthic diatoms are commonly used in this context. However, it is important that the taxonomic information of the separate diatom datasets is compatible. At present, inconsistencies between diatom datasets, mainly due to differences and uncertainties in diatom identification, may misinform diatom taxon-specific ecological preferences, geographical distribution and water quality assessment. It is our opinion that these inconsistencies in diatom datasets can be reduced with quality assurance (QA), such as identification exercises. However, the results of these exercises must be well documented and well communicated; otherwise, gained knowledge may not spread inter-regionally or internationally. As a first step to reach greater consistency in QA/harmonization studies, this article (1) presents and compares information of existing diatom identification and counting QA from published and grey (non-peer reviewed) European literature to identify advantages and drawbacks of each approach; (2) summarizes taxa that can easily be misidentified according to European identification exercises; and (3) suggests a consistent design of identification exercises for diatom dataset QA. © 2016, Springer International Publishing Switzerland.


Posadas E.,University of Valladolid | Szpak D.,University of Valladolid | Lombo F.,University of Oviedo | Dominguez A.,Biogas Fuel Cell S.A. | And 5 more authors.
Journal of Applied Phycology | Year: 2015

The present research was conducted to simultaneously optimize biogas upgrading and carbon and nutrient removal from centrates in a 180-L high-rate algal pond interconnected to an external CO2 absorption unit. Different biogas and centrate supply strategies were assessed to increase biomass lipid content. Results showed 99 % CO2 removal efficiencies from simulated biogas at liquid recirculation rates in the absorption column of 9.9 m3 m−2 h−1, concomitant with nitrogen and phosphorus removal efficiencies of 100 and 82 %, respectively, using a 1:70 diluted centrate at a hydraulic retention time of 7 days. The lipid content of the harvested algal–bacterial biomass remained low (2.9–11.2 %) regardless of the operational conditions, with no particular trend over time. The good settling characteristics of the algal–bacterial flocs resulted in harvesting efficiencies over 95 %, which represents a cost-effective alternative for algal biomass reutilization compared to conventional physical–chemical techniques. Finally, high microalgae biodiversity was found regardless of the operational conditions. © 2015 Springer Science+Business Media Dordrecht


Martin Juarez J.,University of Valladolid | Lorenzo Hernando A.,University of Valladolid | Munoz Torre R.,University of Valladolid | Blanco Lanza S.,The Institute of the Environment | And 2 more authors.
Bioresource Technology | Year: 2016

An enzymatic method for the carbohydrate hydrolysis of different microalgae biomass cultivated in domestic (DWB) and pig manure (PMWB) wastewaters, at different storage conditions (fresh, freeze-dried and reconstituted), was evaluated. The DWB provided sugars yields between 40 and 63%, although low xylose yields (< 23.5%). Approximately 2% of this biomass was converted to byproducts as succinic, acetic and formic acids. For PMWB, a high fraction of the sugars (up to 87%) was extracted, but mainly converted into acetic, butyric and formic acids, which was attributed to the bacterial action. In addition, the performance of an alkaline-peroxide pretreatment, conducted for 1 h, 50 °C and H2O2 concentrations from 1 to 7.5% (w/w), was essayed. The hydrolysis of pretreated microalgae supported a wide range of sugars extraction for DWB (55-90%), and 100% for PMWB. Nevertheless, a large fraction of these sugars (~30% for DWB and 100% for PMWB) was transformed to byproducts. © 2016 Elsevier Ltd.


Liu B.,JiShou University | Liu B.,Xiamen University | Blanco S.,University of León | Blanco S.,The Institute of the Environment | Huang B.,Xiamen University
Phytotaxa | Year: 2015

Two new species in the diatom genus Nitzschia were found in the middle intertidal zone, Xiamen Bay, southern China. Both new taxa belong to the subgenus Nitzschia, as inferred from the presence of a canal-raphe-conopeum system. The valves of both new species are dorsiventral. In Nitzschia arierae sp. nov., the raphe system is positioned centrally, the conopea fuse to the valve face at supporting points, and the zone of valve face subtended by the conopeum has areolae. In Nitzschia gaoi sp. nov., the raphe system is centrally positioned or slightly eccentric, two large conopea extend out from near the raphe while two small conopea extend out from each transverse costa and cover the striae, most part of the zone of valve face subtended by the conopeum has no areolae, and there are two long produced rostrate apices that both arch toward the ventral side or one apex arches and the other is straight. Both new species are epipelic forms inhabiting the coastal environment. © 2015 Magnolia Press.


Posadas E.,University of Valladolid | Garcia-Encina P.A.,University of Valladolid | Dominguez A.,BIOGAS FUEL CELL S.A. | Diaz I.,BIOGAS FUEL CELL S.A. | And 5 more authors.
Ecological Engineering | Year: 2014

The mechanisms underlying carbon and nutrient removal from domestic wastewater in an enclosed tubular and an open biofilm photobioreactors were comparatively evaluated at hydraulic retention times (HRTs) of 10, 7 and 5d, and internal recirculation rates of 4.2 and 9Lm-2min-1. Similar organic carbon removal efficiencies were recorded in both photobioreactors (63-97%) regardless of the operational conditions, while a superior inorganic carbon removal was always achieved in the open biofilm photobioreactor (≈100%). Nitrogen and phosphorous removal decreased in both photobioreactors when decreasing the HRT to 7 and 5d, phosphorus being only efficiently removed in the open photobioreactor. Maximum organic carbon, nitrogen and phosphorus removals of 89±2%, 92±5% and 96±2%, respectively, were achieved in the open biofilm photobioreactor at a HRT of 10d. Assimilation into algal-bacterial biomass accounted for most nitrogen and phosphorous removal in both photobioreactors and for carbon removal in the tubular photobioreactor, while stripping (as a result of the low pHs mediated by an intense NH4 + nitrification) was responsible for most inorganic carbon removal in the open system. No significant differences in the carbon, nitrogen and phosphorus content of the harvested biomass were recorded regardless of the photobioreactor configuration and nutrient loading rates. Finally, the monitoring of the dynamics of microalgae population revealed that open biofilm photobioreactors can support a higher microalgae diversity than their enclosed counterparts. © 2014 Elsevier B.V.


Posadas E.,University of Valladolid | Serejo M.L.,Federal University of Mato Grosso do Sul | Blanco S.,University of León | Blanco S.,The Institute of the Environment | And 3 more authors.
Algal Research | Year: 2015

Novel operational strategies to reduce the O2 concentration in the upgraded biogas were evaluated in a 180L algal-bacterial photobioreactor interconnected to a 2.5L external absorption column during the simultaneous treatment of diluted anaerobically digested or raw vinasse and biogas upgrading. The lowest biomethane O2 levels (0.7±0.2%) were recorded when raw vinasse was fed directly into the absorption column, which resulted in CO2 and H2S removals from biogas of 72±1% and 100±0%, respectively. Process operation at a Hydraulic Retention Time (HRT) of 7d under the above configuration also supported the maximum total carbon, nitrogen and phosphorus removals of 72±4%, 74±3% and 78±5%, respectively. Biomass productivity ranged from 11.4±1.8 to 13.5±2.2gm-2d-1 during microalgae cultivation in diluted anaerobically digested vinasse, while this productivity increased to 16.9±0.7gm-2d-1 when feeding diluted raw vinasse. The good settling characteristics of the algal-bacterial flocs resulted in an average harvesting efficiency of 98.6±0.5% at a HRT in the settler of 23min, regardless of the treated vinasse. The morphological and molecular characterization of the microbial communities showed a high microalgae diversity and bacterial species richness, regardless of the operational conditions (Shannon-Wiener indices ranging from 2.8 to 3.3). © 2015 Elsevier B.V.


Toledo-Cervantes A.,University of Valladolid | Serejo M.L.,Federal University of Mato Grosso do Sul | Blanco S.,University of León | Blanco S.,The Institute of the Environment | And 3 more authors.
Algal Research | Year: 2016

A pilot high rate algal pond (HRAP) interconnected to an external CO2-H2S absorption column via settled broth recirculation was used to simultaneously treat a synthetic digestate and to upgrade biogas to a bio-methane with sufficient quality to be injected into natural gas grids. An innovative HRAP operational strategy with biomass recirculation based on the control of algal-bacterial biomass productivity (2.2, 4.4 and 7.5 g m-2 d-1) via settled biomass wastage was evaluated in order to enhance nutrient recovery from digestate at a constant hydraulic retention time. The influence of the recycling liquid to biogas (L/G) ratio on the quality of the upgraded biogas was assessed. The bio-methane composition under a L/G ratio of 1 (0.4 ± 0.1% CO2, 0.03 ± 0.04% O2, 2.4 ± 0.2% N2 and 97.2 ± 0.2% CH4) complied with the technical specifications of most European bio-methane legislations regardless of the biomass productivity established. The HRAP operational strategy applied allowed increasing the N and P recovery from 19 and 22% to 83 and 100%, respectively, when the biomass productivity was increased from 2.2 to 7.5 g m-2 d-1. Finally, the dynamics of microalgae and bacteria population structure were characterized by morphological identification and Denaturing Gradient Gel Electrophoresis analysis. © 2016 Elsevier B.V.


Alcantara C.,University of Valladolid | Dominguez J.M.,University of Valladolid | Garcia D.,University of Valladolid | Blanco S.,University of León | And 4 more authors.
Bioresource Technology | Year: 2015

Algal-bacterial symbiosis, implemented in an innovative anoxic-aerobic photobioreactor configuration with biomass recycling, supported an efficient removal of total organic carbon (86-90%), inorganic carbon (57-98%) and total nitrogen (68-79%) during synthetic wastewater treatment at a hydraulic and sludge retention times of 2. days and 20. days, respectively. The availability of inorganic carbon in the photobioreactor, determined by its supply in the wastewater and microalgae activity, governed the extent of nitrogen removal by assimilation or nitrification-denitrification. Unexpectedly, nitrate production was negligible despite the high dissolved oxygen concentrations, denitrification being only based on nitrite reduction. Biomass recycling resulted in the enrichment of rapidly settling algal flocs, which supported effluent total suspended solid concentrations below the European Union maximum discharge limits. Finally, the maximum nitrous oxide emissions recorded were far below the emission factors reported for wastewater treatment plants, confirming the environmental sustainability of this innovative photobioreactor in terms of global warming impact. © 2015 Elsevier Ltd.

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