Hexane biodegradation in two-liquid phase bioreactors: High-performance operation based on the use of hydrophobic biomass

An innovative operation mode in two-liquid phase bioreactors (TLPB) for the treatment of volatile organic compounds (VOC) was investigated. This mode was based on confining the biocatalytic activity exclusively in the non-aqueous phase (NAP) by using hydrophobic microorganisms. The TLPB was implemented in a 2.5 L stirred tank reactor using 10% (v/v) of silicone oil as NAP and hexane as model VOC. A stable elimination capacity (EC) of 21.0 ± 2.5 g m⁻³ h⁻¹ (corresponding to a removal efficiency of 80%) was recorded for 26 days. The accumulation of inhibitory metabolites resulted in drastic drops in the elimination capacity (EC) and an unstable performance of the system, hexanol being identified as potential inhibitory metabolite. Aqueous culture broth exchange by fresh mineral salt medium at a dilution rate of 0.2 day⁻¹ allowed maintaining a high and sustained VOC removal performance. Dissolved oxygen concentration measurements revealed that the oxidative metabolism was strongly stimulated by the aqueous broth exchange. The temporary blockage of the gas/water/NAP transfer pathway for O₂ highlighted the paramount role of this pathway on the performance of the TLPB based on hydrophobic microorganisms.     

Biotrickling air filtration of 2-chlorophenol at high loading rates

The degradation of 2-chlorophenol vapours in air was performed in a trickling biofilter packed with ceramic material seeded with the bacterium Pseudomonas pickettii, strain LD1. The system performance was evaluated under varying operating conditions (inlet 2-chlorophenol air concentrations from 0.10 to 3.50 g m^?3, and superficial air velocities of 30.0, 60.0, and 120.0 m h^?1). For all air velocity the maximum degradation rate was obtained for loading rates of 40 g m^?2 h^?1. Higher loading conditions resulted in strong inhibition of microbial activity, particularly severe at high air velocity. Process analysis, performed using data on pollutant concentration profiles along the filter packing obtained under different conditions of inlet concentration and air velocity, proves that best performance (i.e. maximum degradation efficiency and capacity) can be obtained for a narrow range of operating conditions, which can be ensured by proper design of biofilter size (i.e. diameter and height). Kinetic analysis of experimental data confirms that 2-CP inhibits microbial activity in the biofilter bed. Experimental data are satisfactorily fitted by the Haldane kinetic equation up to a critical value of loading rate, beyond which the experimental degradation rate is overestimated by the kinetic model. The inhibition appears to be affected by the loading rate, and the estimated inhibition constant linearly increases with increasing empty bed residence time.     

Hydrological changes in the northern Pantanal caused by the Manso dam: Impact analysis and suggestions for mitigation

Since 1999, the Manso hydropower plant has been regulating the Cuiabá River, which is one of the two main affluents of the northern Pantanal of Mato Grosso, responsible for the flooding of at least 20,000 km² of the world's greatest floodplain. Since the initiation of regular reservoir operation in 2002, discharge at the beginning of the wet season (November–December) has been reduced by about 20%. Current power plant operation increases dry-season discharges from about 100 m³/s to 150 m³/s, resulting in water levels approximately 1 m above those recorded before regulation. Rainy season runoff higher than 400 m³/s is retained in about 6 weeks and the period of drying up is anticipated. Hydrograph analysis in conjunction with a planialtimetric field survey determined that discharge of 240 m³/s is the minimum required to initiate flooding in the Pantanal in the northern Cuiabá River floodplain, while runoff of 355 m³/s is necessary to guarantee consistent flooding of the same. Constrained by positive linear trends in precipitation and discharge, which were detected through a time series analysis of a 68-year period, two reoperation alternatives are proposed, which would not reduce mass balance of power generation, but can guarantee river overflow during the months November through May, minimizing the impact on ecological functions of the floodplain.     

Evaluation of a pilot-scale biotrickling filter as a VOC control technology for the plastic coating sector

The performance and feasibility of a biotrickling filter (BTF) pilot unit for the treatment of exhaust gases from two robotic spray paint booths at a plastic coating facility were investigated. The volatile organic compound (VOC) concentrations in the emissions of the exhaust gases from the paint booths were relatively stable, although the VOC composition depended on the applied solvent-paint formulation in the booths. The pilot plant was operated for one year at empty bed residence times (EBRTs) ranging from 30 to 93 s. The performance of the system was affected by the solvent-paint formulations. An EBRT between 30 and 40 s was enough to meet legal requirements for products containing more than 60% biodegradable compounds, whereas a minimum EBRT of 80 s was required for emissions mainly composed of hydrophobic VOCs. The dynamics of the microbial population was carried out by fluorescence in situ hybridisation (FISH), indicating a high microbial diversity with composition changes associated with the solvent-paint used. The feasibility of the BTF was evaluated, showing that this technology is economically and environmentally competitive in comparison with thermal treatment technology.     

Life-cycle greenhouse gas emissions assessment and extended exergy accounting of a horizontal-flow constructed wetland for municipal wastewater treatment: A case study in Chile

The life-cycle greenhouse gaseous emissions and primary exergy resources consumption associated with a horizontal subsurface flow constructed wetland (HSSF) were investigated. The subject of study was a wetland for municipal wastewater treatment with a 700-person-equivalent capacity. The effects of two types of emergent aquatic macrophytes (Phragmites australis and Schoenoplectus californicus) and seasonality on greenhouse gas (GHG) gas emissions, the environmental remediation cost (ERC) and the specific environmental remediation cost (SERC) were assessed. The results indicate that GHG emissions per capita (12–22 kgCO2eq/p.e/yr) and primary exergy resources consumed (24–27 MJ/m³) for the HSSF are lower than those of a conventional wastewater treatment plant (67.9 kgCO2eq/p.e/yr and 96 MJ/m³). The SERC varied between 176 and 216 MJ/kg biological oxygen demand (BOD₅) removal, which should be further reduced by 20% for an improved BOD₅ removal efficiency above 90%. The low organic matter removal efficiency is associated with a high organic load and low bacterial development. Seasonality has a marked effect on the organic removal efficiency and the SERC, but the macrophyte species does not.     

An LED-based UV-B irradiation system for tiny organisms: System description and demonstration experiment to determine the hatchability of eggs from four Tetranychus spider mite species from Okinawa

We developed a computer-based system for controlling the photoperiod and irradiance of UV-B and white light from a 5 × 5 light-emitting diode (LED) matrix (100 × 100 mm). In this system, the LED matrix was installed in each of four irradiation boxes and controlled by pulse-width modulators so that each box can independently emit UV-B and white light at irradiances of up to 1.5 and 4.0 W m⁻², respectively, or a combination of both light types. We used this system to examine the hatchabilities of the eggs of four Tetranychus spider mite species (T. urticae, T. kanzawai, T. piercei and T. okinawanus) collected from Okinawa Island under UV-B irradiation alone or simultaneous irradiation with white light for 12 h d⁻¹ at 25 °C. Although no eggs of any species hatched under the UV-B irradiation, even when the irradiance was as low as 0.02 W m⁻², the hatchabilities increased to >90% under simultaneous irradiation with 4.0 W m⁻² white light. At 0.06 W m⁻² UV-B, T. okinawanus eggs hatched (15% hatchability) under simultaneous irradiation with white light, whereas other species showed hatchabilities <1%. These results suggest that photolyases activated by white light may reduce UV-B–induced DNA damage in spider mite eggs and that the greater UV-B tolerance of T. okinawanus may explain its dominance on plants in seashore environments, which have a higher risk of exposure to reflected UV-B even on the undersurface of leaves. Our system will be useful for further examination of photophysiological responses of tiny organisms because of its ability to precisely control radiation conditions.     

Continuous biomethanization of agrifood industry waste: A case study in Spain

The anaerobic digestion technology is a biological treatment widely used to reduce the pollution load of wet waste biomass. In this work we present the results obtained by performing extensive experiments of anaerobic digestion of slaughterhouse waste, tomato industry waste and olive oil industry waste in continuous mode, which were designed to demonstrate that anaerobic digestion is an effective technology from an environmental and economic point of view.Biogas yields obtained are between 35.22 and 5.45 Nm³ biogas/m³ olive oil industry waste and tomato industry waste respectively and the slaughterhouse wastes achieve intermediate production, 30.86 Nm³ biogas/m³ municipal slaughterhouse waste and 22.53 Nm³ biogas/m³ Iberian pig slaughterhouse waste. Moreover, it possible to degrade between 63.46 and 75.3% of the initial organic matter.If these results are analyzed, the environmental, energetic economic benefits of anaerobic digestion can be quantified. Biomethanation of all these wastes generated annually in Extremadura could prevent the emission of 134,772 t of equivalent carbon dioxide, generate an energy similar to that provided by 2826 toe and reach payback times from 3.29 to 3.75 years for anaerobic digestion plant designed to treat the wastes generated by a medium-sized industry. So, we have fulfilled all the planned aims.     

Optimization of a simple field method to determine mercury volatilization from soils—Examples of 13 sites in floodplain ecosystems at the Elbe River (Germany)

Mercury fluxes between soil and atmosphere have often been determined by using dynamic flux chambers and micrometeorological methods to assess ecological risks. However, both systems are complex, stationary, and expensive impeding measurements of Hg emissions at various field sites.The mobile, easy to handle, and cost-effective field method to determine total gaseous mercury (TGM), according to [Böhme, F., Rinklebe, J., Stärk, H.-J., Wennrich, R., Mothes, S., Neue, H.-U., 2005. A simple field method to determine mercury volatilisation from soils. Environ. Sci. Pollut. Res. (ESPR), 12: 133–135] creates a drop in air pressure that enhance the Hg emission. We optimized the sampling set-up using an air circulation system resulting in a continuous air flow over the soil surface. Thus, a drop in air pressure can be avoided and the detected TGM emissions are closer to reality. Additional benefits are an in-ground cylinder which inhibits lateral flow of gaseous mercury and the reduced size of the glass socket facilitating handling.To test the suitability of the optimized method, TGM emissions have been quantified on a set of Hg-contaminated riverine soils. Compared with non-polluted soils, mean Hg fluxes were strongly increased (between 138 and 711 ng m^?2 h^?1) and showed high spatial heterogeneity. Due to impacts of multiple environmental conditions that affect TGM emissions, no significant correlations have been found between Hg stocks in bulk soils and Hg fluxes.     

Factors influencing the efficiency of constructed wetlands used for the treatment of intensive trout farm effluent

In this paper the factors influencing treatment performance of subsurface flow constructed wetlands (SSF wetlands) treating aquaculture effluents were identified and quantified. The financial impact of advanced aquaculture effluent treatment with SSF wetlands was calculated.It is the first long-term, commercial-scale trial of SSF wetland treatment for effluents from intensive trout farming, a highly diluted effluent at very high flow rates (mean total phosphorous concentration 0.34 mg L^?1 at 14.3 L s^?1). The 12-month survey provided the opportunity to generate calculation fundamentals for the commercial application of SSF wetlands for aquaculture. Treatment efficiencies of up to 75–86% for total ammonia nitrogen (TAN), biological oxygen demand (BOD₅) and total suspended solids (TSS) were achieved. The daily area retention rate per square meter wetland area was between 2.1 and 4.5 g for TAN and between 30 and 98 g for TSS.The performance of the six wetland cells comprising three replicated hydraulic loading groups (14.5, 6.9, 3.3 m³ m^?2 day^?1) was monitored, offering the possibility to identify factors influencing treatment efficiency through multifactor analysis. These factors turned out to be nutrient inflow concentration, hydraulic loading rate and accumulation of TSS within the wetland bed, the only time-dependent factor. Factors such as vegetation period and fish harvesting were shown to be of significant but negligible importance.Inflow nutrient concentration is determined by production intensity, husbandry conditions, feed quality and any pre-treatment of effluent. Hydraulic load is determined by the space and budget available for SSF construction. TSS accumulation in the wetland is influenced by pre-treatment of the solid fraction prior to the wetland and determines the wetland service lifetime.From these factors the expenses of commercial wetland application can be estimated, leading to a cost increase around €0.20 kg^?1 fish produced (less than 10% of production costs) and therefore confirm the commercial feasibility of SSF wetland treatment.     

Removal of Cu(II) ions by biosorption onto powdered waste sludge (PWS) prior to biological treatment in an activated sludge unit: A statistical design approach

Biological treatment of synthetic wastewater containing Cu(II) ions was realized in an activated sludge unit with pre-adsorption of Cu(II) onto powdered waste sludge (PWS). Box-Behnken experimental design method was used to investigate Cu(II), chemical oxygen demand (COD) and toxicity removal performance of the activated sludge unit under different operating conditions. The independent variables were the solids retention time (SRT, 5–30 d), hydraulic residence time (HRT, 5–25 h), feed Cu(II) concentration (0–50 mg L^?1) and PWS loading rate (0–4 g h^?1) while percent Cu(II), COD, toxicity (TOX) removals and the sludge volume index (SVI) were the objective functions. The data were correlated with a quadratic response function (R² = 0.99). Cu(II), COD and toxicity removals increased with increasing PWS loading rate and SRT while decreasing with the increasing feed Cu(II) concentration and HRT. Optimum conditions resulting in maximum Cu(II), COD, toxicity removals and SVI values were found to be SRT of 30 d, HRT 15 h, PWS loading rate 3 g h^?1 and feed Cu(II) concentration of less than 30 mg L^?1.     

Diurnal exchanges of CO2 and CH4 across the water–atmosphere interface in a water chestnut meadow (Trapa natans L.)

CH₄ and CO₂ fluxes across the water–atmosphere interface were measured over a 24 h day–night cycle in a shallow oxbow lake colonized by the water chestnut (Trapa natans L.) (Lanca di Po, Northern Italy). Only exchanges mediated by macrophytes were measured, whilst gas ebullition was not considered in this study. Measurements were performed from 29 to 30 July 2005 with short incubations, when T. natans stands covered the whole basin surface with a mean dry biomass of 504 ± 91 g m⁻². Overall, the oxbow lake resulted net heterotrophic with plant and microbial respiration largely exceeding carbon fixation by photosynthesis. The water chestnut stand was a net sink of CO₂ during the day-light period (−60.5 ± 8.5 mmol m⁻² d⁻¹) but it was a net source at night (207.6 ± 6.1 mmol m⁻² d⁻¹), when the greatest CO₂ efflux rate was measured across the water surface (28.2 ± 2.4 mmol m⁻² h⁻¹). The highest CH₄ effluxes (6.6 ± 1.8 mmol m⁻² h⁻¹) were determined in the T. natans stand during day-time, whilst CH₄ emissions across the plant-free water surface were greatest at night (6.8 ± 2.1 mmol m⁻² h⁻¹). Therefore, we assumed that the water chestnut enhanced methane delivery to the atmosphere. On a daily basis, the oxbow lake was a net source to the atmosphere of both CO₂ (147.1 ± 10.8 mmol m⁻² d⁻¹) and CH₄ (116.3 ± 8.0 mmol m⁻² d⁻¹).     

Ground level environmental protein concentrations in various ecuadorian environments: Potential uses of aerosolized protein for ecological research

Large quantities of free protein in the environment and other bioaerosols are ubiquitous throughout terrestrial ground level environments and may be integrative indicators of ecosystem status. Samples of ground level bioaerosols were collected from various ecosystems throughout Ecuador, including pristine humid tropical forest (pristine), highly altered secondary humid tropical forest (highly altered), secondary transitional very humid forest (regrowth transitional), and suburban dry montane deforested (suburban deforested). The results explored the sensitivity of localized aerosol protein concentrations to spatial and temporal variations within ecosystems, and their value for assessing environmental change. Ecosystem specific variations in environmental protein concentrations were observed: pristine 0.32 ± 0.09 μg/m³, highly altered 0.07 ± 0.05 μg/m³, regrowth transitional 0.17 ± 0.06 μg/m³, and suburban deforested 0.09 ± 0.04 μg/m³. Additionally, comparisons of intra-environmental differences in seasonal/daily weather (dry season 0.08 ± 0.03 μg/m³ and wet season 0.10 ± 0.04 μg/m³), environmental fragmentation (buffered 0.19 ± 0.06 μg/m³ and edge 0.15 ± 0.06 μg/m³), and sampling height (ground level 0.32 ± 0.09 μg/m³ and 10 m 0.24 ± 0.04 μg/m³) demonstrated the sensitivity of protein concentrations to environmental conditions. Local protein concentrations in altered environments correlated well with satellite-based spectral indices describing vegetation productivity: normalized difference vegetation index (NDVI) (r² = 0.801), net primary production (NPP) (r² = 0.827), leaf area index (LAI) (r² = 0.410). Moreover, protein concentrations distinguished the pristine site, which was not differentiated in spectral indices, potentially due to spectral saturation typical of highly vegetated environments. Bioaerosol concentrations represent an inexpensive method to increase understanding of environmental changes, especially in densely vegetated ecosystems with high canopies or in areas needing high spatial and temporal resolution. Further research to expand understanding of the applicability of bioaerosol concentrations for environmental monitoring is supported by this pilot study.     

Investigating CH4 and N2O emissions from eco-engineering wastewater treatment processes using constructed wetland microcosms

Methane (CH₄) and nitrous oxide (N₂O) are important greenhouse gases, because of their contribution to the global greenhouse effect. The present study assessed emissions of N₂O and CH₄ from constructed wetland microcosms, planted with Phragmites australis and Zizania latifolia, when treating wastewater under different biological oxygen demand (BOD) concentration conditions. The removal rate was 95% for BOD and more than 80% for COD in all three pollutant concentrations, both plants’ removal rates of pollutants were at almost the same level, and both were found to resist BOD concentrations as high as 200 mg L⁻¹. When BOD concentrations fell below 200 mg L⁻¹, the soil plant units reached an average of 80–92% T-N and T-P removal rates; however, as the concentrations increased to 200 mg mg L⁻¹ or when during the initial phases of winter, the removal rates for T-N and T-P decreased to less than 70%. With NH₃-N removal, the influences of BOD concentrations and air temperature were more obvious. When BOD concentrations increased to 100 mg L⁻¹ after October, an obvious decrease in NH₃-N removal was detected; almost no nitrification occurred beginning in December at BOD concentrations of 200 mg mg L⁻¹. N₂O and CH₄ emissions showed obvious seasonal changes; higher emissions were observed with higher BOD concentrations, especially among Z. latifolia units. The enumeration of methane-oxidizing bacteria and methane-producing bacteria was also conducted to investigate their roles in impacting methane emissions and their relationships with plant species. The pollutant purification potentials of P. australis and Z. latifolia plant units during wastewater treatment of different pollutant concentrations occurred at almost the same levels. The nutrient outflow and methane flux were consistently higher with Z. latifolia units and higher concentrations of BOD. The more reductive status and higher biomass of methanogens may be the reason for the lower nitrification and higher CH₄ emissions observed with Z. latifolia units and higher concentration systems. The Z. latifolia root system is shallow, and the activity of methanotrophs is primarily confined to the upper portion of the soil. However, the root system of P. australis is deeper and can oxidize methane to a greater depth. This latter structure is more favorable as it is better for reducing methane emissions from P. australis soil plant systems.     

Evaluation of the effects of light intensity on growth of the benthic dinoflagellate Ostreopsis sp. 1 using a newly developed photoirradiation-culture system and a novel regression analytical method

Benthic dinoflagellates of the genus Ostreopsis are found all over the world in temperate, subtropical, and tropical coastal regions. Our recent studies revealed that a putative “cryptic” species of Ostreopsis ovata is present widely along Japanese coasts. This organism, Ostreopsis sp. 1, possesses palytoxin analogs and thus its toxic blooms may be responsible for potential toxification of marine organisms. To evaluate the bloom dynamics of Ostreopsis sp. 1, the present study examined the growth responses of Ostreopsis sp. 1 strain s0716 to various light intensities (photon flux densities: μmol photons m⁻² s⁻¹) using a newly devised photoirradiation-culture system. This novel system has white light-emitting diodes (LEDs) capable of more closely simulating the wavelength spectrum of light entering the oceanic water column than do fluorescent tubes and halogen lamps. In this system, the light intensity of the white LEDs was reduced through two polarizing filters by varying the rotation angles of the filters. Thereby, the new system was capable of culturing microalgae under well-controlled light intensity conditions. Ostreopsis sp. 1 grew proportionally when light intensity was increased from 49.5 to 199 μmol photons m⁻² s⁻¹, but its growth appeared to be inhibited slightly at ≥263 μmol photons m⁻² s⁻¹. The relationship between observed growth rates and light intensity was calculated at R > 0.99 (P < 0.01) using a regression analysis with a modified equation of the photosynthesis-light intensity (P-L) model. The equation determined the critical light intensities for growth of Ostreopsis sp. 1 and the organism's growth potential as follows: (1) the threshold light intensity for growth: 29.8 μmol photons m⁻² s⁻¹; (2) the optimum light intensity (L_m) giving the maximum growth rate (μ_max = 0.659 divisions day⁻¹): 196 μmol photons m⁻² s⁻¹; (3) the optimum light intensity range (L_opt) giving ≥95% μ_max: 130–330 μmol photons m⁻² s⁻¹; (4) the semi-optimum range (L_sopt) giving ≥80% μ_max: 90 to over 460 μmol photons m⁻² s⁻¹. The L_sopt represents 4.5–23% ambient light intensity present in surface waters off of a temperate region of the Japanese coast, Tosa Bay; putatively, this semi-optimum range of light intensity appears at depth of 12.9–27.8 m. Considering these issues, our data indicate that Ostreopsis sp. 1 in coastal environments may form blooms at ca. ∼28 m depth in regions along Japanese coasts.     

Novel cancer-targeting SPECT/NIRF dual-modality imaging probe 99mTc-PC-1007: Synthesis and biological evaluation

Synthesis, characterization, in vitro and in vivo biological evaluation of a heptamethine cyanine based dual-mode single-photon emission computed tomography (SPECT)/near infrared fluorescence (NIRF) imaging probe ^99mTc-PC-1007 is described. ^99mTc-PC-1007 exhibited preferential accumulation in human breast cancer MCF-7 cells. Cancer-specific SPECT/CT and NIRF imaging of ^99mTc-PC-1007 was performed in a breast cancer xenograft model. The probe uptake ratio of tumor to control (spinal cord) was calculated to be 4.02 ± 0.56 at 6 h post injection (pi) and 8.50 ± 1.41 at 20 h pi (P < 0.0001). Pharmacokinetic parameters such as blood clearance and organ distribution were assessed.     

Hydrogen sulphide removal from air by biotrickling filter using open-pore polyurethane foam as a carrier

A study was conducted on H₂S removal in a biotrickling filter packed with open-pore polyurethane foam. Thiobacillus denitrificans was used as inoculum and a mixed culture population was developed during the process. The inhibitory effect of sulphate concentration (1.8–16.8 g L⁻¹), pH (6.9–8.6), trickling liquid velocity (TLV, 9.1–22.8 m h⁻¹), H₂S inlet concentration (20–157 ppmv) and the empty bed residence time (EBRT, 9–57 s) on the H₂S removal efficiency (RE) were thoroughly investigated. An increase in pH from 6.9 to 8.5 led to a corresponding increase in H₂S removal. In addition, an inhibitory effect of sulphate concentration was observed from 16.8 g L⁻¹ and the maximum elimination capacity was found to be 22 gS m⁻³ h⁻¹ (RE 98%). The RE was constant (98.8 ± 0.30%) for EBRT ≥ 16 s, but a decrease in the EBRT from 16 to 9 s led to a corresponding decrease in RE from 98.2 to 89.6% for a TLV of 9.1 m h⁻¹ and from 97.9 to 94.9% for a TLV of 22.8 m h⁻¹ (inlet load of 11.0 ± 0.2 gS m⁻³ h⁻¹). The sulphur oxidation capacity in the biotrickling filter was not diminished by the presence of other bacteria.     

Effects of irradiance and water flow on formation and growth of spongy and filamentous thalli of Codium fragile

Effects of irradiance and water flow on formation and growth of filamentous and spongy thalli of Codium fragile (Suringar) Hariot growing on vinylon threads were investigated at the laboratory culture. They showed clear differences in their irradiance and water flow requirements for their formation and growth. Spongy thalli were formed from the cultured filamentous thalli only at the high water flow velocity (10 cm s⁻¹). Number of the spongy thalli remarkably increased with increasing irradiance because those at 10, 50 and 100 μmol m⁻² s⁻¹ reached 0, 2 and 76 thalli m⁻¹, respectively, by 10 weeks of culture. In contrast, filamentous thalli were formed from the cultured spongy thalli at 0 and 3 cm s⁻¹, and difference in irradiance had no effect on their formation. Growth of the spongy thalli greatly accelerated under the combination of the high irradiance and high water velocity (200 μmol m⁻² s⁻¹ and 10 cm s⁻¹) because their relative growth rate in wet weight under the condition was two–four times higher than those at the other examined irradiances and water velocities. On the other hand, difference in water velocity had no effect on growth of the filamentous thalli under flowing water, and their growth decelerated at the high irradiance (200 μmol m⁻² s⁻¹). This demonstrates that water flow is a major factor controlling the formation of the spongy and filamentous thalli. The formation and growth of the spongy thalli surely occur under the combination of the high irradiance and fast flowing water. In contrast, the formation of the filamentous thalli occurs in the calm water, and their growth is inhibited under the high irradiance.     

Temporal and seasonal changes in greenhouse gas emissions from a constructed wetland purifying peat mining runoff waters

Constructed wetlands (CW), widely used to remove nutrients from runoff waters, transform some of the carbon and nitrogen they receive into greenhouse gases, carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), and may therefore have adverse atmospheric impacts. We studied seasonal and temporal changes in C degradation and emissions of CH₄ and N₂O of a boreal CW used to purify peat mining runoff waters 5 (in 1992) and 15 (in 2001–2002) years after construction. There was a remarkable change in the cycling of carbon in the wetland as the number of years in operation increased: the mean CH₄ emission tripled from 140 to 400 mg CH₄ m⁻² d⁻¹ and the mean CO₂ release (respiration) doubled from 7270 to 13 600 mg CO₂ m⁻² d⁻¹ in the 10-year period. The reasons for the increased C gas production were the increased plant biomass, which doubled in 10 years, and a 3 °C higher average temperature in 2002 than in 1992. The N₂O fluxes did not change during the study period: the mean emissions were 340 and 450 μg N₂O m⁻² d⁻¹ in 1992 and 2002.     

Pre-treatment of hospital wastewater by coagulation–flocculation and flotation

Coagulation–flocculation and flotation processes were evaluated for the pre-treatment of hospital wastewater, including the removal of 13 pharmaceutical and personal care products (PPCPs). Coagulation–flocculation assays were performed in a Jar-Test device and in a continuous pilot-scale plant. Raw hospital wastewater as well as the effluent from the continuous coagulation plant were treated in a flotation cell. Removal of total suspended solids (TSS) during pre-treatment was very effective, reaching an average removal efficiency of 92% in the combined coagulation–flotation process. Musk fragrances were eliminated to a high degree during batch coagulation–flocculation (tonalide: 83.4 ± 14.3%; galaxolide: 79.2 ± 9.9%; celestolide: 77.7 ± 16.8%), presumably due to their strong lipophilic character which promotes the interaction of these compounds with the lipid fraction of solids. For diclofenac (DCF), naproxen (NPX) and ibuprofen (IBP) maximum removals of 46%, 42% and 23%, respectively, were obtained, while the rest of PPCPs were not affected by the physico-chemical treatment. Flotation of raw wastewater led to slightly worse results compared to coagulation–flocculation, although the combined action of both improved the overall efficiency of the process. The proposed pre-treatment strategy for hospital wastewater is useful for assimilating its conventional physico-chemical characteristics to that of municipal wastewater as well as for reducing the load of some PPCPs into the sewer system.