Increased power generation from primary sludge by a submersible microbial fuel cell and optimum operational conditions

Microbial fuel cells (MFCs) have received attention as a promising renewable energy technology for waste treatment and energy recovery. We tested a submersible MFC with an innovative design capable of generating a stable voltage of 0.250 ± 0.008 V (with a fixed 470 Ω resistor) directly from primary sludge. In a polarization test, the maximum power density was 0.18 W/m² at a current density of 0.8 A/m² with an external resistor of 300 Ω. The anodic solution of the primary sludge needs to be adjusted to a pH 7 for high power generation. The modified primary sludge with an added phosphate buffer prolonged the current generation and increased the power density by 7 and 1.5 times, respectively, in comparison with raw primary sludge. These findings suggest that energy recovery from primary sludge can be maximized using an advanced MFC system with optimum conditions.     

Stackable and submergible microbial fuel cell modules for wastewater treatment

The stackable and submergible microbial fuel cell (SS-MFC) system was fabricated consisting of three MFC modules (#1, #2 and #3) that were immersed in an anaerobic tank as a 30 L anode compartment. Each module consisted of the anion exchange membrane–membrane electrode assembly (A-MEA) and cation exchange membrane-MEA (C-MEA). Two MEAs shared a cathode compartment in the module and the three modules shared a anode compartment The SS-MFC system was operated with two phase. After batch feeding (phase I), the system was operated under continuous mode (phase II) with different organic concentrations (from 50 to 1000 mg/L) and different hydraulic retention times (HRT; from 3.4 to 7.2 h). The SS-MFC system successfully produced a stable voltage. A-MEA generated a lower power density than the C-MEA because of the former’s high activation and resistance loss. C-MEA showed a higher average maximum power density (3.16 W/m³) than A-MEA (2.82 W/m³) at 70 mL/min (HRT of 7.2 h). The current density increased as the organic concentration was increased from 70 to 1000 mg/L in a manner consistent with Monod kinetics. When the HRT was increased from 3.4 to 7.2 h, the power densities of the C-MEAs increased from 34.3–40.9 to 40.7–45.7 mW/m², but those of the A-MEAs decreased from 25.3–48.0 to 27.7–40.9 mW/m². Although power generation was affected by HRT, organic concentrations, and separator types, the proposed SS-MFC modules can be applied to existing wastewater treatment plants.     

Theoretical guidance and experimental confirmation on catalytic tendency of M-CeO2 (M = Zr,Mn, Ru or Cu) for NH3-SCR of NO

Abstract

Herein, we demonstrate that the degrees of catalytic performance of M-CeO₂-based catalysts (M=Mn, Cu, Ru or Zr) for an ammonia selective catalytic reduction (NH₃-SCR) of nitric-oxide (NO) can be estimated using three theoretical terms; (i) an oxygen vacancy formation energy of a catalyst, (ii) an adsorption energy of NO and (iii) an adsorption energy of NH₃. Those terms predict the trend of the catalytic performance as the order; Mn–CeO₂ > Cu–CeO₂ > Ru–CeO₂ > Zr–CeO₂ > CeO₂. To verify the theoretical prediction, the catalysts were synthesized and tested their performances on the NH₃-SCR of NO reaction. The normalized NO conversion rates at low temperatures (100–200 °C) were measured for Mn–CeO₂, Cu–CeO₂, Ru–CeO₂, Zr–CeO₂ and CeO₂ as 2.61–7.46, 1.30–6.82, 0.73–3.02, 0.81–3.31 and 1.55–2.33 mol s^?1 m^?2, respectively. In addition, a concept of a structure-activity relationship analysis shows a strong relationship between theoretical and experimental results. Consequently, an application of predicting the catalytic performance of catalysts from theoretical calculations prior the catalyst synthesis is useful in catalyst design and screening that can reduce time and cost.     

Production of hydrogen from domestic wastewater in a pilot-scale microbial electrolysis cell

Addressing the need to recover energy from the treatment of domestic wastewater, a 120-L microbial electrolysis cell was operated on site in Northern England, using raw domestic wastewater to produce virtually pure hydrogen gas (100?±?6.4 %) for a period of over 3 months. The volumetric loading rate was 0.14 kg of chemical oxygen demand (COD) per cubic metre per day, just below the typical loading rates for activated sludge of 0.2–2 kg?COD?m^?3?day^?1, at an energetic cost of 2.3 kJ/g?COD, which is below the values for activated sludge 2.5–7.2 kJ/g?COD. The reactor produced an equivalent of 0.015 L?H₂?L^?1?day^?1, and recovered around 70 % of the electrical energy input with a coulombic efficiency of 55 %. Although the reactor did not reach the breakeven point of 100 % electrical energy recovery and COD removal was limited, improved hydrogen capture and reactor design could increase the performance levels substantially. Importantly, for the first time, a ‘proof of concept’ has been made, showing that this technology is capable of energy capture as hydrogen gas from low strength domestic wastewaters at ambient temperatures.     

Energy from algae using microbial fuel cells

Bioelectricity production from a phytoplankton, Chlorella vulgaris, and a macrophyte, Ulva lactuca was examined in single chamber microbial fuel cells (MFCs). MFCs were fed with the two algae (as powders), obtaining differences in energy recovery, degradation efficiency, and power densities. C. vulgaris produced more energy generation per substrate mass (2.5 kWh/kg), but U. lactuca was degraded more completely over a batch cycle (73 ± 1% COD). Maximum power densities obtained using either single cycle or multiple cycle methods were 0.98 W/m² (277 W/m³) using C. vulgaris, and 0.76 W/m² (215 W/m³) using U. lactuca. Polarization curves obtained using a common method of linear sweep voltammetry (LSV) overestimated maximum power densities at a scan rate of 1 mV/s. At 0.1 mV/s, however, the LSV polarization data was in better agreement with single‐ and multiple‐cycle polarization curves. The fingerprints of microbial communities developed in reactors had only 11% similarity to inocula and clustered according to the type of bioprocess used. These results demonstrate that algae can in principle, be used as a renewable source of electricity production in MFCs. Biotechnol. Bioeng. 2009;103: 1068–1076. © 2009 Wiley Periodicals, Inc.     

Swainsonine,a novel fungal metabolite: optimization of fermentative production and bioreactor operations using evolutionary programming

The optimization of bioreactor operations towards swainsonine production was performed using an artificial neural network coupled evolutionary program (EP)-based optimization algorithm fitted with experimental one-factor-at-a-time (OFAT) results. The effects of varying agitation (300–500 rpm) and aeration (0.5–2.0 vvm) rates for different incubation hours (72–108 h) were evaluated in bench top bioreactor. Prominent scale-up parameters, gassed power per unit volume (P _g/V _L, W/m³) and volumetric oxygen mass transfer coefficient (K _L a, s^?1) were correlated with optimized conditions. A maximum of 6.59 ± 0.10 μg/mL of swainsonine production was observed at 400 rpm-1.5 vvm at 84 h in OFAT experiments with corresponding P _g/V_L and K _L a values of 91.66 W/m³ and 341.48 × 10^?4 s^?1, respectively. The EP optimization algorithm predicted a maximum of 10.08 μg/mL of swainsonine at 325.47 rpm, 1.99 vvm and 80.75 h against the experimental production of 7.93 ± 0.52 μg/mL at constant K _L a (349.25 × 10^?4 s^?1) and significantly reduced P _g/V _L (33.33 W/m³) drawn by the impellers.     

Biological soil crusts influence carbon release responses following rainfall in a temperate desert,northern China

How soil cover types and rainfall patterns influence carbon (C) release in temperate desert ecosystems has largely been unexplored. We removed intact crusts down to 10 cm from the Shapotou region, China, and measured them in PVC mesocosms, immediately after rainfall. C release rates were measured in soils with four cover types (moss-crusted soil, algae-crusted soil, mixed (composed of moss, algae, and lichen)-crusted soil, and mobile dune sand). We investigated seven different rainfall magnitudes (0–1, 1–2, 2–5, 5–10, 10–15, 15–20, and >20 mm) under natural conditions. C release from all four BSCs increased with increasing rainfall amount. With a rainfall increase from 0 to 45 mm, carbon release amounts increased from 0.13 ± 0.09 to 15.2 ± 1.35 gC m^?2 in moss-crusted soil, 0.08 ± 0.06 to 6.43 ± 1.23 gC m^?2 in algae-crusted soil, 0.11 ± 0.08 to 8.01 ± 0.51 gC m^?2 in mixed-crusted soil, and 0.06 ± 0.04 to 8.47 ± 0.51 gC m^?2 in mobile dune sand, respectively. Immediately following heavy rainfall events (44.9 mm), moss-crusted soils showed significantly higher carbon release rates than algae- and mixed-crusted soils and mobile dune sands, which were 0.95 ± 0.02, 0.30 ± 0.03, 0.13 ± 0.04, and 0.51 ± 0.02 μmol CO₂ m^?2 s^?1, respectively. Changes in rainfall patterns, especially large rain pulses (>10 mm) affect the contributions of different soil cover types to carbon release amounts; moss-crusted soils sustain higher respiration rates than other biological crusts after short-term extreme rainfall events.     

A Review of: “HPLC of Biological Macromolecules (Methods and Applications) K.M. Goodring F.E. Regnier,Eds Marcel Dekker,New York, 1990; hardbound, 676 pages, $150”

An ionically unbound and thermostable polyphenol oxidase (PPO) was extracted from the leaf of Musa paradisiaca. The enzyme was purified 2.54-fold with a total yield of 9.5% by ammonium sulfate precipitation followed by Sephadex G-100 gel filtration chromatography. The purified enzyme exhibited a clear single band on native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS) PAGE. It was found to be monomeric protein with molecular mass of about 40 kD. The zymographic study using crude extract as enzyme source showed a very clear band around 40 kD and a faint band at around 15 kD, which might be isozymes. The enzyme was optimally active at pH 7.0 and 50°C temperature. The enzyme was active in wide range of pH (4.0–9.0) and temperature (30–90°C). From the thermal inactivation studies in the range 60–75°C, the half-life (t_1/2) values of the enzyme ranged from 17 to 77 min. The inactivation energy (Ea) value of PPO was estimated to be 91.3 kJ mol^?1. It showed higher specificity with catechol (K_m = 8 mM) as compared to 4-methylcatechol (K_m = 10 mM). Among metal ions and reagents tested, Cu²⁺, Fe²⁺, Hg²⁺, Mn²⁺, Ni²⁺, protocatechuic acid, and ferrulic acid enhanced the enzyme activity, while K⁺, Na⁺, Co²⁺, kojic acid, ascorbic acid, ethylenediamine tetraacetic acid (EDTA), sodium azide, β-mercaptoethanol, and L-cysteine inhibited the activity of the enzyme.     

Elemental composition of ambient air particles in Taiyuan,China: evaluation of lifetime cancer and non-cancer risks

Abstract

Shanxi is a heavily polluted area in China. Our aim was to analyze the elemental concentration (71 elements) in ambient air in Taiyuan and evaluate cancer and non-cancer risks. Air was sampled in four urban sites and one rural site in the heating season (winter/spring) and summer season (totally 118?days sampling time). Mean total suspended particles (TSP) across all sampling sites were 248 µg/m³ in summer and 478 µg/m³ in winter. The heating season had higher levels of S, Pb, Br, Mn, Se, As, Ni, Cd, and Hg (23.3 µg/m³, 821?ng/m³, 725?ng/m³, 460?ng/m³, 79?ng/m³, 65?ng/m³, 34?ng/m³, 17?ng/m³, and 3.5?ng/m³, respectively) than the summer season (9.6 µg/m³, 276?ng/m³, 138?ng/m³, 283?ng/m³, 0?ng/m³, 21?ng/m³, 21?ng/m³, 6.8?ng/m³, and 0?ng/m³, respectively), except for Cr and Co, of which the levels were higher in summer. Many elements had a high correlation with the TSP level (r?=?0.70–0.96) and S (r?=?0.61–0.95). A health risk assessment demonstrated that Mn and Cr could have a risk of non-cancer effects. Estimated lifetime cancer risks (R_i>10^?6) were observed for As, Cd, Co, Cr, and Ni, indicating that cancer risks from air pollution were relatively high in Taiyuan.     

Diversity of forest plant species at the community and landscape scales in Switzerland

Abstract

Conservation strategies increasingly refer to indicators derived from large biological data. However, such data are often unique with respect to scale and species groups considered. To compare richness patterns emerging from different inventories, we analysed forest species richness at both the landscape and the community scales in Switzerland. Numbers of forest species were displayed using nationwide distributional species data and referring to three different definitions of forest species. The best regression models on a level of four predictor variables ranged between adj. R ² = 0.50 and 0.66 and revealed environmental heterogeneity/energy, substrate (rocky outcrops) and precipitation as best explanatory variables of forest species richness at the landscape scale. A systematic sample of community data (n = 729; 30 m², 200 m², 500 m²) was examined with respect to nationwide community diversity and plot species richness. More than 50% of all plots were assigned to beech forests (Eu-Fagion, Cephalanthero-Fagion, Luzulo-Fagion and Abieti-Fagion), 14% to Norway spruce forests (Vaccinio-Piceion) and 13% to silver fir forests (Piceo-Abietion). Explanatory variables were derived from averaged indicator values per plot, and from biophysical and disturbance factors. The best models for plot species richness using four predictor variables ranged between adj. R ² = 0.31 and 0.34. Light (averaged L-indicator, tree canopy) and substrate (averaged R-indicator and pH) had the highest explanatory power at all community scales. By contrast, the influence of disturbance variables was very small, as only a small portion of plots were affected by this factor. The effects of disturbances caused by extreme events or by management would reduce the tree canopies and lead to an increase in plant species richness at the community scale. Nevertheless, such community scale processes will not change the species richness at the landscape scale. Instead, the variety of different results derived from different biological data confirms the diversity of aspects to consider. Therefore, conservation strategies should refer to value systems.     

Enhancement of electricity production in a mediatorless air–cathode microbial fuel cell using <Emphasis Type="Italic">Klebsiella</Emphasis> sp. IR21

A novel dissimilatory iron-reducing bacteria, Klebsiella sp. IR21, was isolated from the anode biofilm of an MFC reactor. Klebsiella sp. IR21 reduced 27.8 % of ferric iron to ferrous iron demonstrating that Klebsiella sp. IR21 has electron transfer ability. Additionally, Klebsiella sp. IR21 generated electricity forming a biofilm on the anode surface. When a pure culture of Klebsiella sp. IR21 was supplied into a single chamber, air–cathode MFC fed with a mixture of glucose and acetate (500 mg L^?1 COD), 40–60 mV of voltage (17–26 mA m^?2 of current density) was produced. Klebsiella sp. IR21 was also utilized as a biocatalyst to improve the electrical performance of a conventional MFC reactor. A single chamber, air–cathode MFC was fed with reject wastewater (10,000 mg L^?1 COD) from a H₂ fermentation reactor. The average voltage, current density, and power density were 142.9 ± 25.74 mV, 60.5 ± 11.61 mA m^?2, and 8.9 ± 3.65 mW m^?2, respectively, in the MFC without inoculation of Klebsiella sp. IR21. However, these electrical performances of the MFC were significantly increased to 204.7 ± 40.24 mV, 87.5 ± 17.20 mA m^?2, and 18.6 ± 7.23 mW m^?2, respectively, with inoculation of Klebsiella sp. IR21. The results indicate that Klebsiella sp. IR21 can be utilized as a biocatalyst for enhancement of electrical performance in MFC systems.     

A Cost Analysis of Fully Solution‐Processed ITO‐Free Organic Solar Modules

Organic photovoltaics (OPVs) have become a potential candidate for clean and renewable photovoltaic productions. This work examines the current cost drivers and potential avenues to reduce costs for organic solar modules by constructing a comprehensive bottom‐up cost model. The direct manufacturing cost (MC) and the minimum sustainable price (MSP) for an opaque single solar module (SSM) (MC = 187 ¥ m^?2, MSP = 297 ¥ m^?2) and for a tandem solar module (MC = 224 ¥ m^?2, MSP = 438 ¥ m^?2) are analyzed in detail. Within this calculation, the most expensive layers and processing steps are identified and highlighted. Importantly, the low levelized cost of energy (LCOE) value for an SSM with a 10% power conversion efficiency in a 20‐year range from 0.185 to 0.486 ¥ kWh^?1, with a national average of 0.324 ¥ kWh^?1 in China under an average solar irradiance of 1200 kWh m^?2 year^?1. Moreover, the impact on the cost of alternative materials and constructions, process throughputs, module efficiency, and module lifetime, etc., is presented and avenues to further reduce the MSP and LCOE values are indicated. The analysis shows that OPVs can emerge as a competitive alternative to established power generation technologies if the remaining issues (e.g., active layer material cost, module efficiency, and lifetime) can be resolved.     

Seasonal nitrous oxide and methane emissions across a subtropical estuarine salinity gradient

Currently, there is a lack of knowledge about GHG emissions, specifically N₂O and CH₄, in subtropical coastal freshwater wetland and mangroves in the southern hemisphere. In this study, we quantified the gas fluxes and substrate availability in a subtropical coastal wetland off the coast of southeast Queensland, Australia over a complete wet-dry seasonal cycle. Sites were selected along a salinity gradient ranging from marine (34 psu) in a mangrove forest to freshwater (0.05 psu) wetland, encompassing the range of tidal influence. Fluxes were quantified for CH₄ (range ?0.4–483 mg C–CH₄ h^?1 m^?2) and N₂O (?5.5–126.4 μg N–N₂O h^?1 m^?2), with the system acting as an overall source for CH₄ and N₂O (mean N₂O and CH₄ fluxes: 52.8 μg N–N₂O h^?1 m^?2 and 48.7 mg C–CH₄ h^?1 m^?2, respectively). Significantly higher N₂O fluxes were measured during the summer months (summer mean 64.2 ± 22.2 μg N–N₂O h^?1 m^?2; winter mean 33.1 ± 24.4 µg N–N₂O h^–1 m^?2) but not CH₄ fluxes (summer mean 30.2 ± 81.1 mg C–CH₄ h^?1 m^?2; winter mean 37.4 ± 79.6 mg C–CH₄ h^?1 m^?2). The changes with season are primarily driven by temperature and precipitation controls on the dissolved inorganic nitrogen (DIN) concentration. A significant spatial pattern was observed based on location within the study site, with highest fluxes observed in the freshwater tidal wetland and decreasing through the mangrove forest. The dissolved organic carbon (DOC) varied throughout the landscape and was correlated with higher CH₄ fluxes, but this was a nonlinear trend. DIN availability was dominated by N–NH₄ and correlated to changes in N₂O fluxes throughout the landscape. Overall, we did not observe linear relationships between CH₄ and N₂O fluxes and salinity, oxygen or substrate availability along the fresh-marine continuum, suggesting that this ecosystem is a mosaic of processes and responses to environmental changes.     

CNP budgets of a coral-dominated fringing reef at La Réunion,France: coupling of oceanic phosphate and groundwater nitrate

Productivity, nutrient input, nutrient uptake, and release rates were determined for a coral-dominated reef flat at La Réunion, France, to assess the influence of groundwater nitrogen on carbon and nutrient budgets. Water samples were collected offshore in the ocean, at the reef crest and back reef for nutrients, picoplankton, pH, and total alkalinity. Volume transport of ocean water across the reef flat was measured using both current meters and drogues. Groundwater advected onto the reef flat and mixed with incoming ocean water. Metabolic rates for the reef community were determined to be: gross primary production = 1,000 mmol C m⁻² d⁻¹, community respiration = 960 mmol C m⁻² d⁻¹, and community calcification = 210 mmol C m⁻² d⁻¹. Across the reef flat, silicate behaved conservatively, there was net uptake of phosphate (0.06 mmol P m⁻² d⁻¹) and net release of nitrate, ammonia, dissolved and particulate organic nitrogen (total 7.0 mmol N m⁻² d⁻¹). Groundwater nitrate contributed 37% of the increase in nitrate plus ammonia. The first-order mass transfer coefficient of phosphate was 3.3 m d⁻¹, and for nitrate plus ammonia, 5.9 m d⁻¹. Gross N and P uptake from estimates of mass transfer and uptake of particles were 0.37 mmol P m⁻² d⁻¹ and 7.2 mmol N m⁻² d⁻¹, respectively giving an N:P uptake ratio of 20:1. Thus, the elevation of nitrogen across the reef flat maintains a high N:P flux, enhancing algal growth downstream of the transect. We conclude that net community production (40 mmol C m⁻² d⁻¹) was sustained by net uptake of phosphate from the ocean and net uptake of new nitrogen from groundwater.

     

Fine-root seasonal pattern,production and turnover rate of European beech (Fagus sylvatica L.) stands in Italy Prealps: Possible implications of coppice conversion to high forest

Abstract

The aim of this study was to investigate the possible effects of coppice conversion to high forest on the beech fine-root systems. We compared the seasonal pattern of live and dead fine-root mass (d < 2 mm), production and turnover in three beech stands that differed in management practices. Tree density was higher in the 40-year-old coppice stand than in the stands that were converted from coppice to high forest in 1994 and 2004, respectively. We found that a reduction in tree density reduced the total fine-root biomass (Coppice stand, 353.8 g m^?2; Conversion 1994 stand, 203.6 g m^?2; Conversion 2004 stand, 176.2 g m^?2) which continued to be characterised by a bimodal pattern with two major peaks, one in spring and one in early fall. Conversion to high forest may also affect the fine-root soil depth distribution. Both fine-root production and turnover rate were sensitive to management practices. They were lower in the Coppice stand (production 131.5 g m^?2 year^?1; turnover rate 0.41 year^?1) than in the converted stands (1994 Conversion stand: production 232 g m^?2 year^?1, turnover rate 1.06 year^?1; 2004 Conversion stand: production 164.2 g m^?2 year^?1, turnover rate 0.79 year^?1).     

Grain size affects the relationship between species richness and above-ground biomass in semi-arid rangelands

ABSTRACT

Background: Discrepancies in the shape of the productivity–diversity relationship may arise from differences in spatial scale. We hypothesised that there is a grain size effect on the productivity–diversity relationship.

Aims: To determine the effect of three sampling grain sizes on the productivity–diversity relationship.

Methods: We applied generalised linear mixed effect models on community data from 735 vegetation plots in the Taleghan rangelands, Iran, sampled at three grain sizes (0.25, 1 and 2 m²) to ascertain plant productivity-diversity patterns, while accounting for the effects of site, plant community type, disturbance, and life form.

Results: Overall, relationships between biomass and plant species richness were unimodal at grain sizes of 0.25 and 1 m², and asymptotical at 2 m². The spurious occurrence of a single large shrub may overwhelm a small-sized sampling unit, resulting in a high estimate of the sample’s biomass relative to species richness. However, the relationship between biomass and species richness at larger grain sizes is more likely to reach an asymptote.

Conclusions: Shrubs are partly responsible for driving the relationship between plant biomass and species richness. Given that the frequency of shrubs is highly variable between small plots but not so in large plots, their presence may result in unimodal productivity–diversity relationships at small but not at large grain sizes.     

Comparison of RNA- and DNA-based bacterial communities in a lab-scale methane-degrading biocover

Methanotrophs must become established and active in a landfill biocover for successful methane oxidation. A lab-scale biocover with a soil mixture was operated for removal of methane and nonmethane volatile organic compounds, such as dimethyl sulfide (DMS), benzene (B), and toluene (T). The methane elimination capacity was 211?±?40 g?m^?2 d^?1 at inlet loads of 330–516 g?m^?2 d^?1. DMS, B, and T were completely removed at the bottom layer (40–50 cm) with inlet loads of 221.6?±?92.2, 99.6?±?19.5, and 23.4?±?4.9 mg m^?2 d^?1, respectively. The bacterial community was examined based on DNA and RNA using ribosomal tag pyrosequencing. Interestingly, methanotrophs comprised 80 % of the active community (RNA) while 29 % of the counterpart (DNA). Types I and II methanotrophs equally contributed to methane oxidation, and Methylobacter, Methylocaldum, and Methylocystis were dominant in both communities. The DNA vs. RNA comparison suggests that DNA-based analysis alone can lead to a significant underestimation of active members.     

Effect of UV-B radiation on the synthesis of UV-absorbing compounds in a terrestrial cyanobacterium, Nostoc flagelliforme

Effects of two intensities (1 and 5 W?m^?2) of UV-B radiation on the synthesis of UV-absorbing compounds in a terrestrial cyanobacterium Nostoc flagelliforme were investigated. UV-B radiation resulted in lower biomass. Short period (less than 12 h) of UV-B radiation caused an increase of chlorophyll a content, but subsequent duration of treatment (more than 24 h) resulted in a rapid decrease. N. flagelliforme synthesized UV-absorbing compounds such as scytonemin and mycosporine-like amino acids (MAAs) in response to UV-B radiation. Upon 48 h of exposure to UV-B radiation, scytonemin content in cells increased by 103.8 and 164.0 % at 1 and 5 W?m^?2, respectively. Oligosaccharide-linked mycosporine-like amino acids increased by 145.5 % after 12 h at 5 W?m^?2 and 114.5 % after 48 h at 1 W?m^?2 UV-B radiation. HPLC analysis showed that nine MAAs existed in N. flagelliforme cells both from liquid suspension culture and field colony. But the concentration and kinds of them were different. At the two distinct levels of UV-B radiation, the content of particular MAAs increased, declined, or remained unchanged. Moreover, the appearance of two new MAAs was observed.     

Abundance,distribution, and secondary production of the apple snail Pomacea flagellata (Say, 1829) in Bacalar Lake,a tropical karstic system in southern Mexico

Pomacea flagellata is a gastropod conspicuous in freshwater environments, and represents a fishing resource. To assess their abundance, distribution, and secondary production, monthly samplings were carried out in Bacalar Lake from June 2012 to May 2013 at 12 sampling sites. In each site, three random transects were marked parallel to the shore. All snails on transect were collected and shell length and wet weight measured. The highest density occurred in September (1.27 ind.m^?2), lowest in October (0.47 ind.m^?2). Shell lengths ranged from 2 to 56 mm, with recruitment in January–March. Growth parameters were L_∞ 59.50 mm, K 0.65.year^?1; the lifetime span was 3 years. Average biomass reached 5.57 wet g.m^?2 and secondary production was 6.025 wet g.m^?2.year^-1; annual renewal rate P/B 1.08. Highest abundance and secondary production was contributed by individuals between 31 and 41 mm in length. A potential biomass of 25.06 tons of snails was estimated in the lake. Snail densities, secondary production, and turnover were very low during the year, indicating that it is not viable to consider a commercial catch without affecting the population. A ban of 10 years is proposed, and aquaculture practices of snails are recommended to recover the resource.     

Process contribution evaluation for COD removal and energy production from molasses wastewater in a BioH<Subscript>2</Subscript>–BioCH<Subscript>4</Subscript>–MFC-integrated system

In this study, a three-stage-integrated process using the hydrogenic process (BioH₂), methanogenic process (BioCH₄), and a microbial fuel cell (MFC) was operated using molasses wastewater. The contribution of individual processes to chemical oxygen demand (COD) removal and energy production was evaluated. The three-stage integration system was operated at molasses of 20 g-COD L^?1, and each process achieved hydrogen production rate of 1.1 ± 0.24 L-H₂ L^?1 day^?1, methane production rate of 311 ± 18.94 mL-CH₄ L^?1 day^?1, and production rate per electrode surface area of 10.8 ± 1.4 g m^?2 day^?1. The three-stage integration system generated energy production of 32.32 kJ g-COD^?1 and achieved COD removal of 98 %. The contribution of BioH₂, BioCH₄, and the MFC reactor was 20.8, 72.2, and, 7.0 % of the total COD removal, and 18.7, 81.2, and 0.16 % of the total energy production, respectively. The continuous stirred-tank reactor BioH₂ at HRT of 1 day, up-flow anaerobic sludge blanket BioCH₄ at HRT of 2 days, and MFC reactor at HRT of 3 days were decided in 1:2:3 ratios of working volume under hydraulic retention time consideration. This integration system can be applied to various configurations depending on target wastewater inputs, and it is expected to enhance energy recovery and reduce environmental impact of the final effluent.