Performance comparison of experimental constructed wetlands with different filter media and macrophytes treating industrial wastewater contaminated with lead and copper

The aim of this study was to investigate the treatment efficiency of passive vertical-flow wetland filters containing different macrophytes (Phragmites and/or Typha) and granular media with different adsorption capacities. Gravel, sand, granular activated carbon, charcoal and Filtralite (light expanded clay) were used as filter media. Different concentrations of lead and copper sulfate were added to polluted urban stream inflow water to simulate pretreated mine wastewater. The relationships between growth media, microbial and plant communities as well as the reduction of predominantly lead, copper and five-day biochemical oxygen demand (BOD5) were investigated. An analysis of variance showed that concentration reductions (mg l(-1)) of lead, copper and BOD5 were significantly similar for the six experimental wetlands. Microbial diversity was low due to metal pollution and similar for all filters. There appears to be no additional benefit in using adsorption media and macrophytes to enhance biomass performance during the first 10 months of operation.     

Mature experimental constructed wetlands treating urban water receiving high metal loads

The aim was to assess over 2 years the treatment efficiencies of vertical-flow wetland filters containing macrophytes and granular media of different adsorption capacities. Different concentrations of lead and copper sulfate (constant for 1 year each) were added to urban beck inflow water in order to simulate pretreated (pH adjustment assumed) mine wastewater. After 1 year of operation, the inflow concentrations for lead and copper were increased from 1.30 to 2.98 and from 0.98 to 1.93 mg/L, respectively. However, the metal mass load rates (mg/m(2)/d) were increased by a factor of approximately 4.9 for lead and 4.3 for copper. No breakthrough of metals was recorded. Lead and copper accumulated in the biomass of the litter zone and rhizomes of the macrophytes. Furthermore, microbiological activity decreased during the second year of operation. Bioindicators such as ciliated protozoa and zooplankton decreased sharply in numbers but diatoms increased. In conclusion, the use of macrophytes and adsorption media did not significantly enhance the filtration of lead and copper. Particulate lead is removed by filtration processes including straining. Furthermore, some expensive and time-consuming water quality variables can be predicted with less expensive ones such as temperature in order to reduce sampling costs.     

The effect of copper ions on the production of laccase by the fungus Lentinus (Panus) tigrinus

The basidiomycete Lentinus tigrinus was cultured in media containing copper ions added at different growth stages. Copper ions at increased concentrations decelerated of the fungal biomass accumulation. The later Cu²⁺ ions were added, the better the fungal mycelium developed, and the toxic effect of Cu²⁺ was less pronounced. The maximum laccase activity (47 U/ml) was observed in the presence of 1.5–2.0 mM Cu²⁺ added on day 4 of cultivation.     

Side-by-side comparison of horizontal subsurface flow and free water surface flow constructed wetlands and artificial neural network (ANN) modelling approach

A horizontal subsurface flow (HSSF) and a free water surface flow (FWSF) constructed wetlands (4 m² of each) were set up on the campus of Harran University, Sanliurfa, Turkey. The main objective of the research was to compare the performance of two systems to decide the better one for future planning of wastewater treatment system on the campus. Both of the wetland systems were planted with Phragmites australis and Canna indica. During the observation period (10 months), environmental conditions such as pH, temperature and total chemical oxygen demand (COD), soluble COD, total biochemical oxygen demand (BOD), soluble BOD, total suspended solids (TSS), total phosphate (TP), total nitrogen (TN) removal efficiencies of the systems were determined. According to the results, average yearly removal efficiencies for the HSSF and the FWSF, respectively, were as follows: total COD (75.7% and 69.9%), soluble COD (85.4% and 84.3%), total BOD (79.6% and 87.6%), soluble BOD (87.7% and 95.3%), TN (33.2% and 39.4%), and TP (31.5% and 6.5%). Soluble COD and BOD removal efficiencies of both systems increased gradually since the start-up. After nine months of operation, above 90% removal of organic matters were observed. The treatment performances of the HSSF were better than that of the FWSF with regard to the removal of suspended solids and total COD at especially high temperatures. In FWSF systems, COD concentrations extremely exceeded the discharge limit values due to high concentrations of algae in spring months.The performance of the two systems was modelled using an artificial neural network-back-propagation algorithm. The ANN model was competent at providing reasonable match between the measured and the predicted concentrations of total COD (R = 0.90 for HSSF and R = 0.96 for FWSF), soluble COD (R = 0.90 for HSSF and R = 0.74 for FWSF) and total BOD (R = 0.94 for HSSF and R = 0.84 for FWSF) in the effluents of constructed wetlands.     

Constructed wetlands in Queensland: Performance efficiency and nutrient bioaccumulation

Nine pilot wetlands (eight free water surface and one subsurface flow) have been constructed in Queensland as joint projects between the State and Local Governments, to treat municipal wastewater. The wetlands are in several geographical locations which include tropical, subtropical and arid climates. Each wetland is a different configuration and contains a variety of macrophyte types and species. Most species are native and were collected in the locality or self colonised. This paper examines the performance efficiency of the wetlands and nutrient bioaccumulation in wetland plants. Biochemical oxygen demand concentrations were reduced by 17–89% and suspended solids concentrations by 14–77% to produce wetland effluent with BOD less than 12 mg l⁻¹ and suspended solids less than 22 mg l⁻¹. Reduction in total nitrogen concentrations ranged from 18 to 86%, ammonia nitrogen from 8 to 95% and oxidised nitrogen from 55 to 98%, producing effluent with total nitrogen between 1.6 and 18 mg l⁻¹. Reduction in reactive phosphorus concentration was less than 13% in the free water surface systems with concentration in the effluent exceeding the influent in many of the systems over long term operation. In contrast reduction through the single household subsurface system was 65%. Nutrient bioaccumulation was investigated in 60 species. Submerged (Ceratophyllum) and free floating species (duckweed) had the highest tissue nutrient concentrations, followed by the waterlily (Nymphoides indica), aquatic vines (Ipomoea spp., Ludwigia peploides), and waterferns (Ceratopteris, Marsilea). All these species remove nutrients from the water column. Emergent species had lower nutrient concentrations with the highest nutrients occurring in the exotic sedge Cyperus involucratus. Aquatic grasses including Phragmites had higher nutrient content than the sedges. Nitrogen concentrations were higher in leaf/stem tissue compared to the root/rhizome, whereas phosphorus was higher in root/rhizome tissue. Emergent species had a greater biomass than submerged or free floating species and were therefore able to store more nutrients per unit area of wetland. Cropping the shoots of emergent species increased nutrient content in new shoot growth.     

Direct electron transfer from graphite and functionalized gold electrodes to T1 and T2/T3 copper centers of bilirubin oxidase

Direct electron transfer (DET) from bare spectrographic graphite (SPGE) or 3-mercaptopropionic acid-modified gold (MPA-gold) electrodes to Trachyderma tsunodae bilirubin oxidase (BOD) was studied under anaerobic and aerobic conditions by cyclic voltammetry and chronoamperometry. On cyclic voltammograms nonturnover Faradaic signals with midpoint potentials of about 700 mV and 400 mV were clearly observed corresponding to redox transformations of the T1 site and the T2/T3 cluster of the enzyme, respectively. The immobilized BOD was differently oriented on the two electrodes and its catalysis of O₂-electroreduction was also massively different. On SPGE, where most of the enzyme was oriented with the T1 copper site proximal to the carbon with a quite slow ET process, well-pronounced DET-bioelectroreduction of O₂ was observed, starting already at > 700 mV vs. NHE. In contrast, on MPA-gold most of the enzyme was oriented with its T2/T3 copper cluster proximal to the metal. Indeed, there was little DET-based catalysis of O₂-electroreduction, even though the ET between the MPA-gold and the T2/T3 copper cluster of BOD was similar to that observed for the T1 site at SPGE. When BOD actively catalyzes the O₂-electroreduction, the redox potential of its T1 site is 690 mV vs. NHE and that of one of its T2/T3 copper centers is 390 mV vs. NHE. The redox potential of the T2/T3 copper cluster of a resting form of BOD is suggested to be about 360 mV vs. NHE. These values, combined with the observed biocatalytic behavior, strongly suggest an uphill intra-molecular electron transfer from the T1 site to the T2/T3 cluster during the catalytic turnover of the enzyme.     

Effect of heavy metals (Cu,Cd and Pb) on aspartate and alanine aminotransferase in Ruditapes philippinarum (Mollusca: Bivalvia)

The accumulation of cadmium, copper and lead and their effects on aspartate and alanine aminotransferases in digestive gland, gills, foot and soft body in the clam Ruditapes philippinarum were examined. The animals were exposed to different concentrations: Cd (200–600 μg·l⁻¹), Pb (350–700 μg·l⁻¹) and Cu (10–20 μg·l⁻¹) for 7 days. The highest concentrations were found in digestive gland for cadmium and copper, and in gills for lead, and the lowest values were observed in the foot. Aspartate aminotransferase activity (AST), in general, was not inhibited by cadmium, lead or copper during the exposure. Only in clams exposed to cadmium (600 μg·l⁻¹, 7 days) and copper (20 μg·l⁻¹, 5 days) were observed significant differences (P<0.05) in foot and gills, respectively, with respect to control. In the case of alanine aminotransferase activity (ALT), significant differences were observed for cadmium and lead in treated animals with respect to control. With regard to copper, a decrease in ALT was observed in gills and foot exposed to 20 μg·l⁻¹. A significant correlation (P<0.05) was observed between ALT and metal accumulation for cadmium, copper and lead in gills. In the case of soft body, only cadmium and lead showed a significant correlation. In summary, R. philippinarum can be considered a bioindicator species for cadmium and lead accumulation and ALT could be useful as biomarker of sublethal stress for these metals in soft tissues and gills. Only gills can be considered an adequate target tissue for copper.     

Uptake of six heavy metals by oat as influenced by soil type and additions of cadmium,lead, zinc and copper

Summary The influence of heavy metal additions on availability and uptake of cadmium, lead, zinc, copper, manganese and iron by oat was studied. The experiments were carried out as pot experiments using sandy loam, sandy soil and organic soil. Selective extractants were used to remove metals held in different soil fractions.Lead and copper were preferently bound by organics and oxides, zinc by oxides and inorganics, and cadmium by inorganics and organics.Addition of cadmium to the soils resulted in higher cadmium concentrations in all plant parts but lower concentrations of lead, zinc, copper, manganese and iron, and the accumulation indexes of these metals were also lower when cadmium was added to the soil.Addition of cadmium plus lead, zinc and copper resulted in higher cadmium concentrations in leaves and straw of plants grown in sandy loam and sandy soil, but lower concentrations when plants were grown in organic soil as compared with the results when cadmium was added separately. The transfer of cadmium, lead, zinc and copper from soil to plant was greatest from sandy soil, and zinc and cadmium were more mobile in the plant than were lead and copper.Cadmium concentrations in leaves correlated significantly with CaCl₂ and CH₃COOH extractions in sandy loam and sandy soil and with CH₃COOH extractions in organic soil.Generally, the total metal uptake was lowest from organic soil.     

The effect of copper on the growth of wood-rotting fungi and a blue-stain fungus

The effect of copper (II) ions on the growth of three brown-rot fungi, six white-rot fungi and one blue-stain fungus in solid medium was evaluated. The fungi were grown in malt extract agar with different concentrations of copper added, and the radial growth rate was determined. At the end of the incubation period, the mycelial biomass and the media pH were determined. The white-rot and blue-stain fungus grew up to 3 mM and 6 mM copper, respectively and the brown-rot fungi were the only ones that grew up to 10 mM, with higher growth rates than those shown by the other fungi. In general, the brown-rot fungi produced greater acidification in the culture media than the white-rot fungi and blue-stain fungus, and the acidification increased when the amount of copper was increased. The biomass production for the different species, in the absence or presence of copper, was not related to the radial growth rate, and the fungal species that produced the greatest biomass amounts did not correspond to those that presented the highest growth rates. The brown-rot fungi Wolfiporia cocos and Laetiporus sulfureus and blue-stain fungus Ophiostoma sp. demonstrated greater tolerance to high copper concentrations in solid medium than the white-rot fungi, determined as radial growth rate. On the other hand, the highest biomass producers in solid medium with copper added were the white-rot fungi Ganoderma australe and Trametes versicolor and the brown-rot fungus Gloeophyllum trabeum.     

Removal of phosphates by pilot vertical-flow constructed wetlands using a mixture of sand and dolomite as substrate

This study evaluates the performance of a mixture of river sand and dolomite (10:1, w/w) used as substrate in vertical-flow constructed wetlands in removal of phosphates. Two duplicate pilot-scale artificial wetlands (total 4 units) were set up outdoors, planted with Phragmites australis and fed with a synthetic sewage solution, corresponding to medium strength municipal wastewater. The wetlands were fed with two batch (intermittent) operational modes and their effluent was monitored for the presence of soluble phosphates over a period of 3 months. Laboratory (batch) incubation experiments were also carried out separately to ascertain the phosphate adsorption capacity of the two materials (i.e. sand and dolomite). The wetlands were capable to remove more than 45% of initially applied phosphates. Phosphorus accumulation in the wetlands body at the end of the operation period was in the range of 6.5–18%, as compared with the unused media. The Ca Mehlich-III extractable content was also increased, indicating that the removal of phosphates would be mainly attributed to the sorption of orthophosphate ions onto calcium carbonates and/or to the precipitation of orthophosphate ions with calcium ions as the respective insoluble calcium phosphates.     

Removal of malachite green (MG) from aqueous solutions by native and heat-treated anaerobic granular sludge

The performance of native and heat-treated anaerobic granular sludge in removing of malachite green (MG) from aqueous solution was investigated with different conditions, such as pH, ionic strength, initial concentration and temperature. The maximum biosorption was both observed at pH 5.0 on the native and heat-treated anaerobic granular sludge. The ionic strength had negative effect on MG removal. Kinetic studies showed that the biosorption process followed pseudo-second-order and q_e for native and heat-treated anaerobic granular sludge is 61.73 and 59.17 mg/g at initial concentration 150 mg/L, respectively. Intraparticle diffusion model could well illuminate adsorption process and faster adsorption rate of native anaerobic granular sludge than heat-treated anaerobic granular sludge. The equilibrium data were analyzed using Langmuir and Freundlich model, and well fitted Langmuir model. The negative values of ΔG° and ΔH° suggested that the interaction of MG adsorbed by native and heat-treated anaerobic granular sludge was spontaneous and exothermic. Desorption studies revealed that MG could be well removed from anaerobic granular sludge by 1% (v/v) of HCl–alcohol solution.     

What is the role of Phragmites australis in experimental constructed wetland filters treating urban runoff?

The aim of this research was to assess the role of the macrophyte Phragmites australis (Cav.) Trin. ex Steud. in experimental temporarily flooded vertical-flow wetland filters treating urban runoff. For 2 years, hydrated nickel and copper nitrate were added to sieved road runoff to simulate contaminated primary treated urban runoff. During the first year, 5-day biochemical oxygen demand (BOD) removal efficiencies were lower in planted filters than in unplanted filters. However, the BOD removal performances of all filters were virtually similar irrespective of the planting regime during the second year. The nutrient removal performance of planted filters was more efficient and stable throughout the season particularly after the filters matured compared to that of unplanted filters. A substantial amount of nitrogen was also removed by harvesting P. australis, though metals were not, when compared to those retained in the filters. Furthermore, higher concentrations of nickel in the effluent were recorded in the planted filters, despite their ability to take up the heavy metals. P. australis provided undesirable conditions for precipitation of Ni by lowering the pH in the processes. Finally, after applying shock loadings of Cu, higher Cu outflow concentrations were recorded for planted in comparison to unplanted filters.     

Effect of chloroethene concentrations and granular activated carbon on reductive dechlorination rates and growth of Dehalococcoides spp

This study focused on the investigation of (i) the tetrachloroethene (PCE) toxicity threshold of a reductively dechlorinating mixed culture containing Dehalococcoides spp., (ii) the adsorption of PCE on different types of granular activated carbon (GAC), and (iii) the bioavailability and reductive dechlorination in the presence of GAC. The abundance of Dehalococcoides spp. detected by quantitative real-time polymerase chain reaction (qPCR) was found to increase by 2-4 orders of magnitude during degradation of PCE. No degradation occurred at dissolved concentrations beyond 420 μM (70 mg/L). Different adsorption isotherms were determined for thermally and chemically activated carbons. The addition of GAC to biological assays reduced the dissolved PCE concentration below the toxicity threshold. The combination of microbial reductive dechlorination with GAC adsorption proved to be a promising method for remediation of groundwater contaminated by high concentrations of chloroethenes.     

A field study of constructed wetlands for preventing and treating acid mine drainage

The formation of acid mine drainage (AMD) from mine tailings is a severe environmental problem associated with tailings impoundments. The study evaluated the ability of wetlands built on tailings impoundments to prevent AMD formation and to treat already formed AMD, with special emphasis on the role of wetland plants in the remediation process. Four small-scale surface-flow wetlands of different designs, containing either mine tailings or sand, an inflow of AMD or unpolluted water, and with or without emergent plants (Phragmites australis, Carex rostrata, and Eriophorum angustifolium), were constructed at the Kristineberg mine tailings impoundment in northern Sweden in 2004. Water samples were collected every month in 2006 at inflow and outflow in order to analyse metals, sulphate, pH, and redox potential. At the end of 2006, plant and sediment samples were collected to enable the analysis of metal concentrations. The concentrations of Fe, Zn, Cd, and sulphate and pH did not change after passage through the wetlands treating AMD. However, the Cu concentration decreased by 36–57%, with the decrease higher in the presence than in the absence of plants. The study of AMD prevention indicated that metal concentrations in impoundment water tend to decrease as the water passes through the wetland. However, sulphate concentrations increase and the pH decreases in the water, suggesting sulphide oxidation of the mine tailings. On the other hand, wetland plants increased the pH, decreased the redox potential, and increased the metal concentrations in the substrate, despite the fact that metal uptake in the studied wetland plants accounted for only 0.002–2.9% of the annual metal loading into the wetlands, suggesting that plants promote metal sedimentation and adsorption. Emergent plants and the wetlands constructed in this study were thus inadequate to treat the very harsh AMD at the Kristineberg mine site.     

Cobalt toxicity in anaerobic granular sludge: influence of chemical speciation

The influence of cobalt speciation on the toxicity of cobalt to methylotrophic methanogenesis in anaerobic granular sludge was investigated. The cobalt speciation was studied with three different media that contained varying concentrations of complexing ligands [carbonates, phosphates and ethylenediaminetetraacetic acid (EDTA)]. Three fractions (nominal added, dissolved and free) of cobalt were determined in the liquid media and were correlated with data from batch toxicity experiments. The average concentration of cobalt that was required for 50% inhibition of methanogenic activity (IC₅₀) for free Co²⁺ in the three sets of measurements was 13 μmol/L with a standard deviation of 22% and a similarity of 72% between the data obtained in the three different media for the range of cobalt concentrations investigated. The standard deviation of the IC₅₀ for the other two fractions was much higher, i.e. 85 and 144% for the added cobalt and dissolved cobalt, respectively, and the similarity was almost 0% for both fractions. Complexation (and precipitation) with EDTA, phosphates and carbonates was shown to decrease the toxicity of cobalt on methylotrophic methanogenesis. The free cobalt concentration is proposed to be the key parameter to correlate with cobalt toxicity. Thus, the toxicity of cobalt to granular sludge can be estimated based on the equilibrium-free cobalt concentration.     

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.     

Biosorption of copper,lead and nickel on immobilized Bacillus coagulans using experimental design methodologies

Biosorption of copper, lead and nickel onto immobilized Bacillus coagulans (IBC) from aqueous solution in single- and multi-metal systems was investigated. The results of scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDXA) and Fourier transform infrared (FTIR) spectrometry demonstrated the importance of surface morphology and identified the active groups involved in adsorption. In batch studies, the most significant factors were screened by Minimum Run Res V Design. The Simplex Lattice Mixture Design was then successfully applied to explore the maximum adsorption capacity of the three metals (75.3 mg/g for copper, 118.3 mg/g for lead and 68.4 mg/g for nickel) and the preferential adsorption of IBC followed the order: Pb (II)?>?Cu (II)?>?Ni (II). Furthermore, adsorption kinetics and adsorption isotherms of single-, binary-, and ternary-metal systems were studied and the experimental data was found to fit well to the Freundlich isotherm and pseudo-second-order kinetics.     

Effects of sucrose concentration and exogenous hormones on growth and periplocin accumulation in adventitious roots of Periploca sepium Bunge

Periploca sepium adventitious roots were cultured on 0.5 Murashige and Skoog solid media supplemented with exogenous hormones of different types and various concentrations, and with sucrose of different concentrations. Auxins (indole butyric acid (IBA) and naphthalene acetic acid (NAA)) and cytokinins (6-benzylaminopurine (BA) and kinetin (KT)) were selected as exogenous hormones for adventitious root proliferation. Compared with other hormones, IBA was the suitable auxin for adventitious root proliferation. Under this circumstance, every root explant generates 10?C15 adventitious roots (1- to 2-cm long) after 30?days. However, nothing but callus was induced on the root explants when NAA was added into the medium and the same result was achieved when auxins (IBA or NAA) were added into the media together with cytokinins (BA or KT). The suitable concentration of IBA for adventitious root proliferation was 1?C2?mg/l, when every root explant generated 10?C20 adventitious roots (1- to 2-cm long). The optimum concentration of IBA for periplocin accumulation was 1?mg/l, when the periplocin content reached 95.46???g/g. With regard to the investigation of sucrose concentration, 2?C3% (w/v) sucrose was favorable for adventitious root proliferation as every root explant in this concentration generated 10?C20 adventitious roots (1- to 2-cm long). The highest periplocin content (101.56???g/g) was achieved at 5% (w/v) sucrose, whereas the periplocin content at 5% (w/v) sucrose did not show significant difference from the periplocin content (95.38 and 98.47???g/g, respectively) at 3% (w/v) or 4% (w/v) sucrose.     

Treatment of domestic wastewater and production of commercial flowers in vertical and horizontal subsurface-flow constructed wetlands

In developing countries, the use of non-conventional plant species as emergent plants in constructed wetlands may add economic benefits besides treating wastewater. In this work, the use of four commercial-valuable ornamental species (Zantedeschia aethiopica, Strelitzia reginae, Anturium andreanum and Agapanthus africanus) was investigated in two types of subsurface wetlands for domestic wastewater treatment. Several water quality parameters were evaluated at the inlet and outlets of a pilot-scale system. Physical measurements were used to evaluate and compare the development of the ornamental plants under two patterns of flow in subsurface wetlands.The results for pollutant removal were significantly higher in the vertical subsurface-flow constructed wetlands (VFCW) for most pollutants. The average removals were more than 80% for BOD and COD; 50.6% for Org-N; 72.2% for NH₄⁺, 50% for Total-P and 96.9% for TC. Only two pollutants were removed in statistically higher percentages in the horizontal subsurface-flow constructed wetlands (HFCW) (NO₃^?, 47.7% and TSS, 82%). The pollutant removal efficiencies were similar to the results obtained in many studies with conventional macrophytes. Most ornamental plants survived the 12-month period of experimentation and their development depended on the type of constructed wetland they were planted. Z. aethiopica looked healthier and produced around 60 flowers in the HFCW. The other three species developed better in the VFCW, although A. andreanum died during the winter. S. reginae produced healthier flowers (and more) and bigger leaves and A. Agapanthus produced more leaves and more lasting flowers. This suggests that it is possible to produce commercial flowers in constructed wetlands without reducing the efficiency of the treatment system.     

Biochar successfully replaces activated charcoal for in vitro culture of two white poplar clones reducing ethylene concentration

Biochar (BC) is a carbon rich product resulting from the biomass pyrolysis process and there have been no reports until now on BC effects in tissue cultures as a suitable substitute for activated charcoal (AC). The results of an experiment on two clones of white poplar (Populus alba L.) grown in culture media with different amounts of BC (0, 0.5 and 1.5?g/dm³) showed that its addition did not damage the plants and there were no significant differences comparing the data obtained for the same concentrations of AC. Both BC and AC addition was shown to increase root dry biomass and number of roots per shoot and these effects appeared to be independent of genotype and concentrations of the added products. A greater elongation was also recorded for shoots grown on a substrate containing BC than those grown on media without BC. These effects did not seem to be caused by darkening due to the addition of BC as there are no significant differences between the temperatures of the different culture media, but are probably due to the adsorption of molecules such as ethylene. Indeed, during the experiment, the hormone concentration in the atmosphere was lower in vials containing the media with BC than the BC-free ones after 14 and 21?days: the lower amount of ethylene in the medium with BC could explain the difference in shoot elongation and the abundant root biomass since high ethylene concentration could inhibit organogenesis.