- I received a PhD in chemical engineering from the University of Birmingham (UK), BEng and MEng from Tianjin Universit... moreI received a PhD in chemical engineering from the University of Birmingham (UK), BEng and MEng from Tianjin University (China). My primary research activities are in constructed wetlands for water pollution control. I also conduct research in environmental nanotechnology and water resources management.edit
Water quality safety is the key factor to maintain the ecosystem service functions of lakes. Field investigations and statistical analyses were carried out to study the water quality of a large, agriculture-stressed lakes (e.g., Chagan... more
Water quality safety is the key factor to maintain the ecosystem service functions of lakes. Field investigations and statistical analyses were carried out to study the water quality of a large, agriculture-stressed lakes (e.g., Chagan Lake) in Northeast China. The hydro-chemical properties of the Chagan Lake are HCO 3 ·CO 3-Na. Nutrient (N and P) and non-nutrient (pH and F −) were found to be the major factors that threaten water quality safety of the lake. The concentration of total nitrogen (TN) and total phosphorus (TP) was found to vary seasonally and at different locations. The overall lake water had mean TN and TP values of 2.19 mg/L and 0.49 mg/L, respectively, in summer. TN was the major factor for water quality deterioration in the western region of the lake, while TP was the principal factor in the other regions, as determined by a principal component analysis (PCA). Fluoride (F −) concentration in the lake water were related to the values of total dissolved solid (TDS), pH, and electrical conductivity (EC). In addition, eutrophication is a fundamental index that has been affecting the ecological evaluation of water quality. The results showed that trophic level index (TLI), trophic state index (TSI), and eutrophication index (EI) were evaluated to quantify the risk of eutrophication. However, TLI and TSI can better describe the purification effect of the wetland. These indices showed that the lake water was hyper-eutrophic in summer, with TLI, TSI, and EI values of 60.1, 63.0, and 66.6, respectively. Disparities in water quality were observed among whole areas of the lake. Overall, this study revealed that controlling agriculture drainage is crucial for lake water quality management. The study generated critical data for making water quality management plans to control the risk.
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The amount of the precipitated air inside a flotation tank has a significant effect on the removal efficiency of a dissolved air flotation (DAF) system. For the first time, this study examined the effect of salinity (35 g L-1) and... more
The amount of the precipitated air inside a flotation tank has a significant effect on the removal efficiency of a dissolved air flotation (DAF) system. For the first time, this study examined the effect of salinity (35 g L-1) and temperature variations (10°C-40°C) on air solubility in an unpacked air sat-urator of a real-scale DAF system for different range of pressures (300-600 kPa) and recycle ratios (10%-40%). The amount of dissolved air inside the air saturator was measured using the liquid displacement method. The results indicated that, under equilibrium conditions, salinity and temperature are inversely proportional to air solubility. However, under non-equilibrium status, with increases in temperature, the amount of dissolved air declines to its minimum value at 20°C and then increased again. The observed behaviour was attributed to the effect of temperature on volumetric gas/liquid mass transfer (K L a). The effects of recycle ratio and pressure was also investigated for non-equilibrium conditions and it was observed that the temperatures was below 20°C, an increase in recycle ratio and saturator pressure can compensate the lack of air caused by salinity and increase of temperature. However, for temperatures above 20°C, it is not necessary to increase the recycle ratio and saturator pressure as the rise of temperature by itself increases air concentration. Finally, the size distribution of microbubbles was also investigated and it was found that temperature does not affect the average size of microbubbles noticeably whereas salinity prevents coalescence and contributes to smaller size bubbles.
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Water environment pollution by human activities is one of the major factors leading to today’s water crisis. Compared with traditional wastewater treatment technologies, constructed wetlands have expanded more rapidly due to various... more
Water environment pollution by human activities is one of the major factors leading to today’s water crisis. Compared with traditional wastewater treatment technologies, constructed wetlands have expanded more rapidly due to various advantages that they have, such as low cost, simple maintenance, aesthetic and environmental friendly nature. Despite their rapidly increasing applications, the design of constructed wetlands needs significantly improvement towards more scientific, model-based approach, which is now an important issue of research and development. This paper investigates the mechanisms of pollutant removal in constructed wetlands that are directly affected by substrates, vegetations and water flow patterns. New, conceptual design methods are proposed, based on domestic and overseas experiences, and the impacts of several key design factors are discussed, to improve constructed wetland design.
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This study reports on batch adsorption experiments aimed at sequestration of Pb(II) ions from synthetic wastewater at low concentrations onto canola stalk. The surface of the canola stalk was analysed using Fourier transform infrared... more
This study reports on batch adsorption experiments aimed at sequestration of Pb(II) ions from synthetic wastewater at low concentrations onto canola stalk. The surface of the canola stalk was analysed using Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy systems. The sorption efficiency of the canola stalk for the elimination of lead ions was investigated for a range of pHs, contact times, concentration of lead ions and canola stalk dosages. The experimental data were evaluated applying the Freundlich, Langmuir, Harkins-Jura, Redlich-Peterson and Halsey isotherm equations. The results fitted excellently into the Freundlich and Halsey isotherm models. The Freundlich maximum multilayer sorption capacity was obtained to be 10.923 mg/g. The dynamic mechanism of lead adsorption was investigated over time using pseudo-second-order, pseudo-first-order, Elovich, fractional power and intraparticle diffusion kinetic models. The kinetic study indicated the adsorption data best fitted into the pseudo-second-order equation. The final results demonstrated the effective and fast sorption performance of canola stalk as a low cost and natural adsorbent to treat lead-contaminated wastewater.
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Solutions containing dissolved organic carbon (DOC) from a depressional wetland that receives agricultural drainage water were incubated in pure quartz sands with FeCl 3 added as the main electron acceptor. The effects of three factors... more
Solutions containing dissolved organic carbon (DOC) from a depressional wetland that receives agricultural drainage water were incubated in pure quartz sands with FeCl 3 added as the main electron acceptor. The effects of three factors (the water, DOC, and Fe contents) on the CO 2 and CH 4 production rates, integrated cumulative C emissions and Fe-OC co-precipitation were studied. The results showed that CO 2 production during the DOC mineralization process was facilitated by Fe(III) reduction at the expense of CH 4 production. Additionally, the cumulative CO 2 emissions determined by integrating the temporal curves of CO 2 production were negatively correlated with those of CH 4 (r = −0.48, p < 0.01). Extremely large ratios of the CO 2 :CH 4 production rate (13,762 and 44,885 under two soil water conditions: saturation and flood conditions of twice the saturation level) were observed. These ratios were likely caused by simultaneous anaerobic fermentation, microbial respiration , and methanogenesis suppression triggered by iron reduction. The effects of exogenous Fe(III) inputs on total C emissions (as the sum of integrated cumulative CO 2 and CH 4) were only dependent on soil water conditions during the initial period of the experiment, and flooded conditions increased total C emissions by as much as double. Increased ratios of Fe inputs to C contents were found to proportionally increase the total C emissions (R 2 = 0.32, p < 0.01). Under saturated conditions, the co-precipitation of Fe-OC complexes prevented the remainder of the DOC from undergoing mineralization. In terms of DOC, we concluded that wetland saturation with introduced Fe(III) can reduce total C emissions from anaerobic respiration and promote C se-questration.
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An experimental study was carried out using in pilot-scale constructed wetland systems, operated in parallel to treat raw sewage. Each system consisted of a vertical flow (VF) unit that was filled with biochar as the main media, followed... more
An experimental study was carried out using in pilot-scale constructed wetland systems, operated in parallel to treat raw sewage. Each system consisted of a vertical flow (VF) unit that was filled with biochar as the main media, followed by a horizontal flow (HF) unit filled with crushed cement mortar. Hydraulic loading (HL) ranged 340-680 mm/day was applied on the VF wetland units, where high total nitrogen (TN) mass removal rate (20-23 g N/m 2 d) was obtained, demonstrating that biochar media had a beneficial effect on the degradation of nitrogenous pollutants. Total phosphorus (TP) removal percentage (concentration based) was ≥ 86% in HF wetlands packed with mortar materials. In one system, the flow direction of the sewage was directed by the deployment of downflow pipes and vertical baffles, aiming to facilitate the formation of aerobic and anaerobic zones in the wetland matrices. The effects of such arrangement were analyzed by comparing pollutant removal efficiencies in the two systems. On average, 99, 96, 93, and 86 percentage removals were obtained for ammonia (NH 4-N), TN, biochemical oxygen demand (BOD), and TP, respectively, during the experiments. Biochar and crushed mortar proved to be a highly effective combination as media in subsurface flow constructed wetlands for wastewater treatment.
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In the case of increasing fragmentation of wetlands, the study of the relationship between wetland landscape characteristics and total nitrogen (TN) in water is of great significance to reveal the mechanism of wetland water purification.... more
In the case of increasing fragmentation of wetlands, the study of the relationship between wetland landscape characteristics and total nitrogen (TN) in water is of great significance to reveal the mechanism of wetland water purification. Taking the Naoli River (NR) wetlands in Northeast China as the research object, 10 uniformly distributed sampling sites in the study area were sampled in August 2015 to test the TN concentration and interpret the images of NR wetlands in the same period. Taking the sampling site as the control point, the whole wetlands were divided into 10 regions, and the landscape index of each region was extracted. In order to reveal whether the landscape characteristics are related to the TN concentration in the wetlands water body, the landscape index and the TN concentration in the control point water body were analyzed by correlation analysis, step-by-step elimination analysis and path analysis to reveal whether the landscape characteristics are related to the TN concentration under wetlands receiving agricultural drainages. The results showed that the correlation coefficients between four area indexes or eight shape indexes and TN concentration did not reach a significant correlation level (P > 0.05), indicating that TN removal was not only determined by a single landscape index. The path coefficient of edge density (ED) index is-0.41, indicating that wetland patch connectivity is the primary factor of TN removal, and there is no relationship between the larger patch area and the higher TN removal. The removal of TN in wetlands is restricted by the synergistic effect of landscape area and shape characteristics.
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In this study, calcium-alginate beads impregnated with nano zero valent iron (NZVI), magnetite nanoparticles (MNP), and powdered activated carbon (PAC) were synthesized, as they were mixed with calcium carbonate powders in sodium alginate... more
In this study, calcium-alginate beads impregnated with nano zero valent iron (NZVI), magnetite nanoparticles (MNP), and powdered activated carbon (PAC) were synthesized, as they were mixed with calcium carbonate powders in sodium alginate solution and reacted with calcium chloride and citric acid. Optical and scanning electron microscopy (SEM) images showed that the nanoparticles were uniformly embedded, and gas bubbles formed, in the polymeric beads. Comparative experiments were carried out as the nanoparticles were dosed, in original (bare) or immobilized form (embedded in the beads), into 100 mg/L nitrate-nitrogen (NO3-N) solutions at 5, 10, and 15 g/L. In 48 h, each gram of immobilized NZVI in the beads were found to reduce 4.3-9.6 mg NO3-N to ammoniacal-nitrogen (NH4-N). Up to 47.8% NH4-N resulted from NO3-N reduction was immobilized by PAC in the beads. These results demonstrated the effectiveness of using the beads for in-situ removal of nitrate, potentially producing an alternative technique to treat nitrate contaminated waters under anaerobic condition.
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Water quality safety is the key factor to maintain the ecosystem service functions of lakes. Field investigations and statistical analyses were carried out to study the water quality of a large, agriculture-stressed lakes (e.g., Chagan... more
Water quality safety is the key factor to maintain the ecosystem service functions of lakes. Field investigations and statistical analyses were carried out to study the water quality of a large, agriculture-stressed lakes (e.g., Chagan Lake) in Northeast China. The hydro-chemical properties of the Chagan Lake are HCO 3 ·CO 3-Na. Nutrient (N and P) and non-nutrient (pH and F −) were found to be the major factors that threaten water quality safety of the lake. The concentration of total nitrogen (TN) and total phosphorus (TP) was found to vary seasonally and at different locations. The overall lake water had mean TN and TP values of 2.19 mg/L and 0.49 mg/L, respectively, in summer. TN was the major factor for water quality deterioration in the western region of the lake, while TP was the principal factor in the other regions, as determined by a principal component analysis (PCA). Fluoride (F −) concentration in the lake water were related to the values of total dissolved solid (TDS), pH, and electrical conductivity (EC). In addition, eutrophication is a fundamental index that has been affecting the ecological evaluation of water quality. The results showed that trophic level index (TLI), trophic state index (TSI), and eutrophication index (EI) were evaluated to quantify the risk of eutrophication. However, TLI and TSI can better describe the purification effect of the wetland. These indices showed that the lake water was hyper-eutrophic in summer, with TLI, TSI, and EI values of 60.1, 63.0, and 66.6, respectively. Disparities in water quality were observed among whole areas of the lake. Overall, this study revealed that controlling agriculture drainage is crucial for lake water quality management. The study generated critical data for making water quality management plans to control the risk.
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Bio-hydrogen production (BHP) produced from renewable bio-resources is an attractive route for green energy production, due to its compelling advantages of relative high efficiency, cost-effectiveness, and lower ecological impact. This... more
Bio-hydrogen production (BHP) produced from renewable bio-resources is an attractive route for green energy production, due to its compelling advantages of relative high efficiency, cost-effectiveness, and lower ecological impact. This study reviewed different BHP pathways, and the most important enzymes involved in these pathways, to identify technological gaps and effective approaches for process intensification in industrial applications. Among the various approaches reviewed in this study, a particular focus was set on the latest methods of chemicals/metal addition for improving hydrogen generation during dark fermentation (DF) processes; the up-to-date findings of different chemicals/metal addition methods have been quantitatively evaluated and thoroughly compared in this paper. A new efficiency evaluation criterion is also proposed, allowing different BHP processes to be compared with greater simplicity and validity.
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This paper reports pollutant removal performances from mixed industrial wastewater employing sub-surface flow constructed wetland systems in Bangladesh. Two parallel hybrid wetland trains were established; each train included a vertical... more
This paper reports pollutant removal performances from mixed industrial wastewater employing sub-surface flow constructed wetland systems in Bangladesh. Two parallel hybrid wetland trains were established; each train included a vertical flow (VF) followed by a horizontal flow (HF) wetland. One hybrid system was packed with construction materials (i.e. recycled bricks), whereas the other system included agricultural by-products (i.e. sugarcane bagasse). All wetland units were planted with Canna indica. The hybrid trains were operated under non recirculation and recirculation phases; input hydraulic loading across each VF system ranged between 219.3 and 438.0 mm/d. Mean nitrogen, organics, solids, phosphorus and color removals across the hybrid systems were 67.5e80.0, 74.0e85.0, 55.0e95.0, 64.0 e89.0 and 46.0e83.0% respectively. Lower input biodegradation ratio influenced organics removal routes in wetland systems that employed recycled bricks. In contrast, organic contents of sugarcane bagasse material supported microbial routes in the other system. VF wetland with organic media achieved higher TN removal rates (1.82 g/m 2 d), due to internal carbon (C) generation. Higher phosphorus removals (89.0%) were observed in hybrid system packed with recycled brick media, due to adsorption process. HF wetland packed with recycled brick was efficient in removing color compounds, whereas the other HF system (with organic media) showed high sulfate removals. Nitrogen and BOD removal improvement was observed in VF wetland (packed with recycled brick media) during recirculation period; in contrast, effluent recirculation reduced removal rates of such pollutants in VF system that employed organic media. In general, this study shows potential application of particular materials as the main media of wetland systems, to achieve pollutant removals from industrial wastewaters in Bangladesh.
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Purpose Artificial aeration changes the redox conditions at the soil surface. The introduction of iron (Fe) into wetlands can influence carbon (C) and phosphorus (P) cycling under the fluctuating redox conditions. However, artificial Fe... more
Purpose Artificial aeration changes the redox conditions at the soil surface. The introduction of iron (Fe) into wetlands can influence carbon (C) and phosphorus (P) cycling under the fluctuating redox conditions. However, artificial Fe introduced into wetlands is uncommon, and there are no Fe dose guidelines. We compared aerobic and anaerobic conditions to test the hypothesis that Fe addition can, although redox-dependent, affect P forms and the coupling of organic C. Materials and methods Twenty-four intact soil cores were collected randomly from a lacustrine wetland of Lake Xiaoxingkai. And representative and homogeneous seedlings of Glyceria spiculosa were collected. The incubation was designed with two treatment factors: Fe/P ratio (5 or 10) and high and low dissolved oxygen (DO) concentrations (> 6 and < 2 mg L −1 , respectively). Four groups with three replicates were separated randomly and labeled as aerobic + plant treatment, anaerobic + plant treatment, and aerobic or anaerobic treatment (control). Results and discussion The DO concentrations were stratified, decreasing with soil depth and increasing with time, especially under aerobic conditions. The Eh values generally increased with fluctuations under aerobic conditions. The artificial aeration substantially changed the redox environment at the water-soil interface. Of the total P, 45% was in the reactive Fe-bound P, indicating that Lake Xiaoxingkai had high internal P loading. No significant differences were observed in total Fe, amorphous Fe, and organic C at the soil surface between the two Fe/P ratios; however, a significant difference in free Fe was observed. And soil amorphous Fe was found to be a significant correlation with soil organic C, indicating that iron oxides were related with the soil chemical properties. Conclusions After short-term incubation, Fe addition can affect the cycling of major elements in wetlands, although this effect is redox dependent. Excessive Fe doses may result in regional environmental risks, such as eutrophication and C sinks of wetland ecosystems. Large-scale controlled experiments are needed to fully understand the behaviors of soil elements in wetlands.
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Purpose Ferrihydrite (Fh) and calcite were used as reactive capping layers for a eutrophic lake. The effectiveness of Fh and/or calcite capping for demobilizing phosphorus (P) in the sediment from the overlying water was tested, and the... more
Purpose Ferrihydrite (Fh) and calcite were used as reactive capping layers for a eutrophic lake. The effectiveness of Fh and/or calcite capping for demobilizing phosphorus (P) in the sediment from the overlying water was tested, and the responses of carbon (C), nitrogen (N), and iron (Fe) to different capping treatments were analyzed as well. Materials and methods Twelve sediment cores were collected randomly using polycarbonate tubes from Ornamental Lake in the Royal Botanic Gardens of Melbourne, Australia. Four groups with three replicates were separated randomly and labeled as the control (no capping), calcite (capped with 1-cm-deep calcite), Fh (capped with 1-cm-deep synthesized Fh powder), and calcite + Fh (CaFh, capped with 0.5-cm-deep Fh powder first and then with 0.5-cm-deep calcite). Gentle bubbling was employed to prevent anoxic conditions in the sediments and stimulate vascular plant ventilation during a 15-day static incubation. The overlying water sample mixed by a small magnetic stirrer was withdrawn 1, 3, 7, 11, and 15 days after capping for the analyses of filterable reactive phosphorus (FRP), filterable N, and Fe species. Results and discussion The results showed that CaFh had a greater effect on the FRP removal in the overlying water than Fh alone. No significant Fe release was observed for Fh and CaFh compared to the control and calcite. The introduction of Fh increased the release of ammonium and total N. After incubation, no significant differences were observed among total P, total N, and organic carbon in the upper sediments, except for total Fe. Conclusions Composite capping with Fh and calcite could be used as an effective, low-cost natural method to block the release of P from the sediment without a significant Fe pollution risk. The potential environmental risks need further attention.
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A hybrid porous adsorbent was produced by mixing black liquor lignin (BL) with basic oxygen furnace steelmaking slag (SS) followed by carbonization at 8608C for removal of trace sulfur dioxide (SO 2) from air. The effects of BL percentage... more
A hybrid porous adsorbent was produced by mixing black liquor lignin (BL) with basic oxygen furnace steelmaking slag (SS) followed by carbonization at 8608C for removal of trace sulfur dioxide (SO 2) from air. The effects of BL percentage , carbonization temperature, carbonization duration and the binary combined effect of each individual process parameter on the removal of SO 2 have been statistically analyzed. The optimal preparation conditions were 48% 5 BL/ (BL 1 SS), carbonized at 8608C for 50 minutes (labeled BL-SS-48-860-50). The crystallite CaO and MgO phases remained in the hybrid matrix. A carbonization temperature over 8008C facilitated gasification reaction between the carbon matrix and the CO 2 emitted from the decomposition of calcium and magnesium carbonate, which led to the pore formation and enlargement in the carbon matrix. The prepared hybrid adsorbent showed good SO 2 removal performance. The kinetic model demonstrated satisfying results in predicting SO 2 adsorption kinetics with good prediction within a relative large range of SO 2 inlet concentration. The mass transfer coefficient k 5 537 (s 21) was obtained by fitting the model to the experimental breakthrough curve.
This article reports pollutant removal performances of baffled subsurface flow, and integrated surface flow-floating treatment wetland units, when arranged in series for the treatment of municipal wastewater in Bangladesh. The wetland... more
This article reports pollutant removal performances of baffled subsurface flow, and integrated surface flow-floating treatment wetland units, when arranged in series for the treatment of municipal wastewater in Bangladesh. The wetland units (of the hybrid system) included organic, inorganic media, and were planted with nineteen types of macrophytes. The wetland train was operated under hydraulic loading fluctuation and seasonal variation. The performance analyses (across the wetland units) illustrated simultaneous denitrification and organics removal rates in the first stage vertical flow wetland, due to organic carbon leaching from the employed organic media. Higher mean organics removal rates (656.0 g COD/(m 2 ·day)) did not completely inhibit nitrification in the first stage vertical flow system; such pattern could be linked to effective utilization of the trapped oxygen, as the flow was directed throughout the media by the baffle walls. Second stage horizontal flow wetland showed enhanced biodegradable organics removal, which depleted organic carbon availability for denitrification. The final stage integrated wetland system allowed further nitrogen removal from wastewater, via nutrient uptake by plant roots (along with nitrification), and generation of organic carbon (by the dead macrophytes) to support denitrification. The system achieved higher E. coli mortality through protozoa predation, E. coli oxidation, and destruction by UV radiation. In general, enhanced pollutant removal efficiencies as demonstrated by the structurally modified hybrid wetland system signify the necessity of such modification, when operated under adverse conditions such as: substantial input organics loading, hydraulic loading fluctuation, and seasonal variation.
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This paper provides a comprehensive review on organics and nutrients (N and P) removals from industrial, municipal, domestic, secondary treated, and decentralized wastewaters employing subsurface flow wetlands. The review indicates that... more
This paper provides a comprehensive review on organics and nutrients (N and P) removals from industrial, municipal, domestic, secondary treated, and decentralized wastewaters employing subsurface flow wetlands. The review indicates that novel operational strategies, structural modification, and internal carbon generation enhanced nitrogen and organics removals across such reviewed systems. Phosphorus removals were critically dependent on specific P-adsorbing materials. The review further illustrates that subsurface flow wetlands could meet reuse standards in decentralized clusters. Reasons and remedies of major operational problems (media clogging and seasonal variations) have also been analyzed. Different operational strategies have been identified to achieve higher removal rates.
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Two lab-scale wetland systems were studied for the removal of dissolved Cu, Mn, Fe, Pb and Zn. Vegetated with Typha domingensis, each system consisted of two units, a vertical and a horizontal flow wetland column, which were filled with... more
Two lab-scale wetland systems were studied for the removal of dissolved Cu, Mn, Fe, Pb and Zn. Vegetated with Typha domingensis, each system consisted of two units, a vertical and a horizontal flow wetland column, which were filled with either crushed sea shell grits or composted green waste as main media. A synthetic acidic wastewater was prepared by dissolving H 2 SO 4 , Pb(CH 3 COO) 2 , MnCl 2 , FeSO 4 , CuSO 4 and ZnSO 4 in a distilled water. As it passed through each column, metal concentrations, pH and conductivity were monitored. The pH value of the wastewater increased in the shell grit columns, where dissolved metals were almost completely (> 99%) removed. In the wetland columns filled with the green waste, the average percentage removals were 90, 77, 27, 98 and 75% for Cu, Mn, Fe, Pb and Zn, respectively. Scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) analysis showed that the surface characteristics of the shell grits remained largely unchanged before and after being used in the columns; but the mass compositions of carbon increased, whereas calcium and oxygen decreased. Infrared spectroscopy (IR) and X-ray diffraction (XRD) were used to further analyse the chemical compositions and functional groups of the surfaces of the shell grits.
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Unsaturated wetland system showed higher nitrification and organics removals. Denitrification was achieved through internal organic carbon generation. Unsaturated vertical flow system was efficient at lower input hydraulic loadings.... more
Unsaturated wetland system showed higher nitrification and organics removals. Denitrification was achieved through internal organic carbon generation. Unsaturated vertical flow system was efficient at lower input hydraulic loadings. Saturated systems illustrated higher nitrogen removals at greater input loadings. Sulfate and coliform removals were influenced by environmental parameters. a b s t r a c t This paper provides a comparative evaluation between unsaturated and partially saturated vertical flow (VF) wetlands, that were employed to investigate nitrogen, organics, sulfate and coliform removals from municipal wastewater. The wetlands included organic straw materials as the main media and were planted with Canna indica species. Media saturation proportion in partially saturated systems ranged between 15.0 and 45.0% (with respect to media volume). Performance analyses indicated simultaneous nitrogen (52.7%) and biodegradable organics (47.0%) removals in unsaturated VF wetland. Mean ammo-niacal nitrogen (NH 4-N) and total nitrogen (TN) removal rates were recorded as 1.30 and 1.26 g/m 2 d, respectively. Organic carbon (C) leaching from the straw media supported denitrification of the nitrified products in unsaturated system. In contrast, nitrification was the limiting step in partially saturated VF wetlands due to the development of anoxic/anaerobic conditions inside the media. Nitrogen removal percentages ranged between 29.0 and 42.0% between these wetlands. Decrease of aerobic zones also reduced aerobic organic removals in these systems. Nitrogen and organics removals improved across unsaturated VF wetland, when input hydraulic loadings were 50.0% reduced. In contrast, saturated VF wetlands showed lower nitrogen removal rates when subjected to reduced hydraulic loadings, probably due to uneven distribution of wastewater flow (inside the media). Partially saturated VF system (with 45.0% saturation ratio) showed higher sulfate removals (41.6%); mean sulfate removal rate was 0.75 g/m 2 d. Anaerobic conditions of such wetland coupled with C availability from the straw media allowed observed removals. Coliform mortality was higher in VF wetlands that were operated under more aerobic conditions.
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This study aimed to assess the quantity and quality of water in a surface flow constructed wetland in Australia's far north Queensland. Owing to tropical climate in the region, the wetland provided dual functions: retention of a... more
This study aimed to assess the quantity and quality of water in a surface flow constructed wetland in Australia's far north Queensland. Owing to tropical climate in the region, the wetland provided dual functions: retention of a treated wastewater for zero discharge during the dry season and tertiary treatment prior to discharge during the wet season. Rainfall data, permeability of wetland soil, evaporation, inflow and outflow were analysed in a water balance analysis; the results showed that based on a 72-year-average rainfall pattern, daily wastewater inflow of 85 m(3)/d is the maximum this wetland can cope with without breaching its discharge certificate. In water quality analysis, the K-C* model was used to predict changes of biochemical oxygen demand (BOD, suspended solids (SS), total nitrogen (TN), total phosphorus (TP) and faecal coliforms (FC) in the wetland. Model predictions were compared with field sampling results. It was found that the wetland was effective in remov...
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Nitrification was the major route of NH 4-N removal in the FCW. C leaching from the hanging roots supported denitrification in the FCW. Nutrient removals were higher in dry season due to higher influent concentration. Maturity of the... more
Nitrification was the major route of NH 4-N removal in the FCW. C leaching from the hanging roots supported denitrification in the FCW. Nutrient removals were higher in dry season due to higher influent concentration. Maturity of the hanging roots controlled removals during shock loadings. FCW systems are potential technologies for polluted surface water treatment. a b s t r a c t This paper reports the performance of a pilot scale floating constructed wetland (FCW), employed for the treatment of polluted water collected from Buriganga river in Bangladesh. The FCW system included a tank for accommodating collected water and a floating mat with media, to support the growth of two macrophyte species Phragmites australis and Canna indica. Mean mass removal rates of 0.66, 0.76, 0.08, 0.51, 2.49 g/m 2 d were achieved for ammoniacal nitrogen (NH 4-N), total inorganic nitrogen (TIN), phosphorus (P), biochemical oxygen demand (BOD), chemical oxygen demand (COD), respectively by the FCW. Nitrogen removal was via nitrification-denitrification processes, whereas filtration–sedimentation appeared to influence phosphorus removal. The system achieved substantial Escherichia coli mortality rates, through protozoa predation and oxidation processes. Higher influent concentrations during dry period allowed greater removal of nutrients and E. coli. Hydraulic shock-loading experiment revealed critical interdependency between hanging roots maturity, input hydraulic, and pollutant loadings for maintaining stable performances.
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The variation of climate elements and its relationship with wetland landscape in western Jilin Province (WJL) were studied to support decision-making for drought prevention and ecology protection. Mann-Kendall test and linear regression... more
The variation of climate elements and its relationship with wetland landscape in western Jilin Province (WJL) were studied to support decision-making for drought prevention and ecology protection. Mann-Kendall test and linear regression algorithm methods were used to analyze the characteristics of climate change, using a large amount of data of temperature, precipitation, evapotranspiration and dry-wet index, collected from nine monitoring stations during 1960-2014. The results showed that annual temperature and dry-wet index in WJL displayed a ascendant tendency, with the average rate of 0.34℃/10a and 0.14/10a, respectively. The annual precipitation and potential evapotranspiration showed a declining trend; decreasing by about-7.92mm/10a and-3.4mm/10a, respectively. Homogeneous trend was found for temperature and evapotranspiration in the autumn; an increasing trend observed. A sharp declining trend was found in the summer season for precipitation, which was the biggest contributor to the overall decrease of annual precipitation. The spatial distribution of annual and seasonal climate factors indicated that the WJL area is becoming drier, especially in the summer and autumn seasons. The wetland landscape indexes in most regions are significantly correclated with summer precipitation. The significance level for I, II and IV regions located in the west of WJL reached 99%. It is important to plan responding measures of water resource management, to counter the decrease of summer precipitation in western WJL, and reduce the impact of drought and wetlands degradation, which is possibly caused by the global climate change.
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The main removal mechanisms for the degradations of seven pollutants in wastewater treatment wetlands were analysed,and a mathematical model was established to quantify the removal of each pollutant,based on its main removal... more
The main removal mechanisms for the degradations of seven pollutants in wastewater treatment wetlands were analysed,and a mathematical model was established to quantify the removal of each pollutant,based on its main removal mechanisms.Subsurface horizontal flow wetlands were treated as a series of continuous stirred-tank reactors(CSTRs).Kinetic models for the removal of biochemical oxygen demand,chemical oxygen demand,ammonia,total nitrogen and faecal coliforms were established by combining Monod or first-order kinetics with CSTR assumptions.These tentative models account for a wide range of factors that affect wetland performance,but the models have not been proven by experiment data.Depending on the derivation of various coefficients in the models and verification by actual performance data,this study may provide a starting point for an integrated pollutant removal model to be developed,and experimentally verified,thereby making a step forward from the current greenbox'approa...
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Assessment on the interaction between groundwater and surface water (GW-SW) can generate information that is critical to regional water resource management, especially for regions that are highly dependent on groundwater resources for... more
Assessment on the interaction between groundwater and surface water (GW-SW) can generate information that is critical to regional water resource management, especially for regions that are highly dependent on groundwater resources for irrigation. This study investigated such interaction on China's Sanjiang Plain (10.9 × 10(4) km(2)) and produced results to assist sustainable regional water management for intensive agricultural activities. Methods of hierarchical cluster analysis (HCA), principal component analysis (PCA), and statistical analysis were used in this study. One hundred two water samplings (60 from shallow groundwater, 7 from deep groundwater, and 35 from surface water) were collected and grouped into three clusters and seven sub-clusters during the analyses. The PCA analysis identified four principal components of the interaction, which explained 85.9 % variance of total database, attributed to the dissolution and evolution of gypsum, feldspar, and other natural min...
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The presence of arsenic and heavy metals in drinking water sources poses a serious health risk due to chronic toxicological effects. Constructed wetlands have the potential to remove arsenic and heavy metals, but little is known about... more
The presence of arsenic and heavy metals in drinking water sources poses a serious health risk due to chronic toxicological effects. Constructed wetlands have the potential to remove arsenic and heavy metals, but little is known about pollutant removal efficiency and reliability of wetlands for this task. This lab-scale study investigated the use of vertical subsurface flow constructed wetlands for removing arsenic, boron, copper, zinc, iron and manganese from synthetic wastewater. Gravel, limestone, zeolite and cocopeat were employed as wetland media. Conventional gravel media only showed limited capability in removing arsenic, iron, copper and zinc; and it showed virtually no capability in removing manganese and boron. In contrast, alternative wetland media: cocopeat, zeolite and limestone, demonstrated significant efficiencies--in terms of percentage removal and mass rate per m3 of wetland volume--for removing arsenic, iron, manganese, copper and zinc; their ability to remove boron, in terms of mass removal rate, was also higher than that of the gravel media. The overall results demonstrated the potential of using vertical flow wetlands to remove arsenic and metals from contaminated water, having cocopeat, zeolite or limestone as supporting media.
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A gravel-based tidal flow reed bed system was operated with three different strategies in order to investigate its optimal performance for the treatment of a high strength agricultural wastewater. According to the three strategies,... more
A gravel-based tidal flow reed bed system was operated with three different strategies in order to investigate its optimal performance for the treatment of a high strength agricultural wastewater. According to the three strategies, individual reed beds were saturated and unsaturated with the wastewater for different periods while reasonably stable hydraulic and organic loadings were maintained. Experimental results demonstrated that the system produced the highest pollutant removal efficiencies with a relatively short saturated period and long unsaturated period, highlighting the importance of oxygen transfer into reed bed matrices during the treatment. Significant removals of some major organic and inorganic pollutants were achieved under all three operational conditions. Nitrification was not the major route of ammoniacal-nitrogen removal when the system was under high organic loading. Due to the filtration of suspended solids and the accumulation of biomass, gradual clogging of the reed bed matrices took place, which caused concerns over the long-term efficiency of the tidal flow system.
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A laboratory-scale, mass-balance study was carried out on the transformation of nitrogenous pollutants in four vertical flow wetland columns. Landfill leachate containing low organic matter, but a high concentration of... more
A laboratory-scale, mass-balance study was carried out on the transformation of nitrogenous pollutants in four vertical flow wetland columns. Landfill leachate containing low organic matter, but a high concentration of ammoniacal-nitrogen, was treated under dissolved oxygen concentrations close to saturation. Influent total nitrogen (TN) comprised ammoniacal-nitrogen with less than 1% nitrate and nitrite, negligible organic nitrogen, and very low BOD. Nitrification occurred in three of the four columns. There was a substantial loss of total nitrogen (52%) in one column, whereas other columns exhibited zero to minor losses (< 12%). Nitrogen loss under study conditions was unexpected. Two hypotheses are proposed to account for it: (1) either the loss of TN is attributed to nitrogen transformation into a form (provisionally termed alpha-nitrogen) that is undetectable by the analytical methods used; or (2) the loss is caused by microbial denitrification or deammonification. By elimination and stoichiometric mass balance calculations, completely autotrophic nitrogen-removal over nitrite (CANON) deammonification is confirmed as responsible for nitrogen loss in one column. This result reveals that CANON can be native to aerobic engineered wetland systems treating high ammonia, low organic content wastewater.
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This paper provides a comparative evaluation of the kinetic models that were developed to describe the biodegradation of nitrogen and organics removal in wetland systems. Reaction kinetics that were considered in the model development... more
This paper provides a comparative evaluation of the kinetic models that were developed to describe the biodegradation of nitrogen and organics removal in wetland systems. Reaction kinetics that were considered in the model development included first order kinetics, Monod and multiple Monod kinetics; these kinetics were combined with continuous-stirred tank reactor (CSTR) or plug flow pattern to produce equations to link inlet and outlet concentrations of each key pollutants across a single wetland. Using three statistical parameters, a critical evaluation of five potential models was made for vertical and horizontal flow wetlands. The results recommended the models that were developed based on Monod models, for predicting the removal of nitrogen and organics in a vertical and horizontal flow wetland system. No clear correlation was observed between influent BOD/COD values and kinetic coefficients of BOD5 in VF and HF wetlands, illustrating that the removal of biodegradable organics was insensitive to the nature of organic matter. Higher effluent COD/TN values coincided with greater denitrification kinetic coefficients, signifying the dependency of denitrification on the availability of COD in VF wetland systems. In contrast, the trend was opposite in HF wetlands, indicating that availability of NO3-N was the main limiting step for nitrogen removal. Overall, the results suggested the possible application of the developed alternative predictive models, for understanding the complex biodegradation routes of nitrogen and organics removal in VF and HF wetland systems.► Developing alternative kinetic models for modelling the removal of nitrogen and organics in vertical and horizontal flow wetlands, which eventually improves the current understanding of pollutant removal dynamics in wetland systems. ► Demonstrating the dependency of nitrogen and organics removal on multiple limiting factors in subsurface flow wetlands. ► Determining kinetic coefficients for efficient design of wetland systems to remove pollutants.
Research Interests: Water, Wetlands, Kinetics, Rheology, Multidisciplinary, and 17 moreNitrates, Regression Analysis, Nitrogen, First-Order Logic, Prediction Model, Model development, Constructed Wetland, Bioreactors, Reproducibility of Results, Continuous stirred tank reactor, Lumping Kinetic Model, Flow Pattern, Organic Matter, Reaction Kinetics, Nitrogen Removal, Organic Chemicals, and Biological Oxygen Demand Analysis
Arsenic pollution in aquatic environments is a worldwide concern due to its toxicity and chronic effects on human health. This concern has generated increasing interest in the use of different treatment technologies to remove arsenic from... more
Arsenic pollution in aquatic environments is a worldwide concern due to its toxicity and chronic effects on human health. This concern has generated increasing interest in the use of different treatment technologies to remove arsenic from contaminated water. Constructed wetlands are a cost-effective natural system successfully used for removing various pollutants, and they have shown capability for removing arsenic. This paper reviews current understanding of the removal processes for arsenic, discusses implications for treatment wetlands, and identifies critical knowledge gaps and areas worthy of future research. The reactivity of arsenic means that different arsenic species may be found in wetlands, influenced by vegetation, supporting medium and microorganisms. Despite the fact that sorption, precipitation and coprecipitation are the principal processes responsible for the removal of arsenic, bacteria can mediate these processes and can play a significant role under favourable environmental conditions. The most important factors affecting the speciation of arsenic are pH, alkalinity, temperature, dissolved oxygen, the presence of other chemical species – iron, sulphur, phosphate –, a source of carbon, and the wetland substrate. Studies of the microbial communities and the speciation of arsenic in the solid phase using advanced techniques could provide further insights on the removal of arsenic. Limited data and understanding of the interaction of the different processes involved in the removal of arsenic explain the rudimentary guidelines available for the design of wetlands systems.► Constructed wetlands are capable to remove As. ► The main removal mechanisms are precipitation, coprecipitation and sorption. ► Bacteria can mediate these removal processes under favourable conditions. ► Factors affecting As speciation include pH, DO, Fe, S, P, TOC, wetland media. ► Knowledge of the different processes involved is required to improve wetlands design.
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This paper reports a comparative study of four kinetic models that can be applied in the design of subsurface horizontal flow reed beds for wastewater treatment. The models were developed from different combinations of Monod kinetics,... more
This paper reports a comparative study of four kinetic models that can be applied in the design of subsurface horizontal flow reed beds for wastewater treatment. The models were developed from different combinations of Monod kinetics, first-order kinetics, continuous stirred-tank reactor and plug flow patterns. Using three statistical parameters (coefficient of determination, relative root mean square error, and model efficiency), critical examinations were made on the accuracy of these models. For predicting organic matter removal, the combination of Monod kinetics with plug flow pattern gave the closest match between theoretical predictions and actual performances of 80 horizontal flow reed beds. In all four models, the coefficients of BOD removal were found to increase slightly with BOD loading. The ratios of BOD/COD had no correlation with the coefficients, indicating that in the horizontal flow reed beds the degradation of organic matter is insensitive to the nature of organics in the wastewater.
Research Interests: Design, Kinetics, Wastewater Treatment, Biodegradation, Wastewater, and 18 moreRoot-Mean Square Error, First-Order Logic, Process biochemistry, Microbial Degradation, Accuracy, Constructed Wetland, BoD, Sewage Treatment, Continuous stirred tank reactor, Coefficient of Determination, Chemical Oxygen Demand, Lumping Kinetic Model, Flow Pattern, Organic Matter, Simulation Models, Biochemical Oxygen Demand, Biochemistry and cell biology, and Reed Bed
This study investigated three lab-scale hybrid wetland systems with traditional (gravel) and alternative substrates (wood mulch and zeolite) for removing organic, inorganic pollutants and coliforms from a synthetic wastewater, in order to... more
This study investigated three lab-scale hybrid wetland systems with traditional (gravel) and alternative substrates (wood mulch and zeolite) for removing organic, inorganic pollutants and coliforms from a synthetic wastewater, in order to investigate the efficiency of alternative substrates, and monitor the stability of system performance. The hybrid systems were operated under controlled variations of hydraulic load (q, 0.3–0.9 m3/m2 d), influent ammoniacal nitrogen (NH4–N, 22.0–80.0 mg/L), total nitrogen (TN, 24.0–84.0 mg/L) and biodegradable organics concentration (BOD5, 14.5–102.0 mg/L). Overall, mulch and zeolite showed promising prospect as wetland substrates, as both media enhanced the removal of nitrogen and organics. Average NH4–N, TN and BOD5 removal percentages were over 99%, 72% and 97%, respectively, across all three systems, indicating stable removal performances regardless of variable operating conditions. Higher Escherichia coli removal efficiencies (99.9%) were observed across the three systems, probably due to dominancy of aerobic conditions in vertical wetland columns of the hybrid systems.
Research Interests: Wetlands, Carbon, Water Purification, Rheology, Stability, and 19 moreMultidisciplinary, Zeolites, Nitrification, Wood, Hybrid, Escherichia coli, Wetland, Denitrification, Nitrates, Nitrogen, Constructed Wetland, Oxygen, Operant Conditioning, System performance, Total Nitrogen, Oxidation-Reduction, Organic Chemicals, Biological Oxygen Demand Analysis, and Hybrid System
A mass-balance study was carried out to investigate the transformation of nitrogenous pollutants in vertical flow wetlands. Landfill leachate containing low BOD, but a high concentration of ammonia, was treated in four wetland columns... more
A mass-balance study was carried out to investigate the transformation of nitrogenous pollutants in vertical flow wetlands. Landfill leachate containing low BOD, but a high concentration of ammonia, was treated in four wetland columns under predominately aerobic conditions. Influent total nitrogen in the leachate consisted mainly of ammonia with less than 1% nitrate and nitrite, and negligible organic nitrogen. There was a substantial loss of total nitrogen (52%) in one column, whereas other columns exhibited zero to minor losses (<12%). Net nitrogen loss under study conditions was unexpected. Correlations between pH, nitrite and nitrate concentrations indicated the removal of nitrogen under study conditions did not follow the conventional, simplistic, chemistry of autotrophic nitrification. Through mass-balance analysis, it was found that CANON (Completely Autotrophic Nitrogen-removal Over Nitrite) was responsible for the transformation of nitrogen into gaseous form, thereby causing the loss of nitrogen mass. The results show that CANON can be native to aerobic engineered wetland systems treating wastewater that contains high ammonia and low BOD.
Research Interests: Microbiology, Water, Wetlands, Carbon, Biomass, and 20 moreWastewater Treatment, Multidisciplinary, Nitrates, Nitrogen, Plant Roots, Poaceae, Ammonia, Steady state, Constructed Wetland, Fluorescent in situ hybridization, Bioreactors, Total Nitrogen, Sequencing Batch Reactor, Nitrogen Removal, Landfill Leachate, Hydrogen-Ion Concentration, Carbon Source, Nitrites, Mass Balance, and Reed Bed
With the unique advantages of lower operational and maintenance cost, the applications of subsurface flow constructed wetlands for the treatment of wastewater have been increasing rapidly throughout the world. The removal of nitrogen and... more
With the unique advantages of lower operational and maintenance cost, the applications of subsurface flow constructed wetlands for the treatment of wastewater have been increasing rapidly throughout the world. The removal of nitrogen and organics by such systems has gained substantial attention in recent years. In subsurface flow wetlands, the removal of pollutants often relies on a diverse range of co-existing physical, chemical and biological routes, which are vitally dependent on numerous environmental and operational parameters. This paper provides a comprehensive review of wetland structures, classic and novel nitrogen and organics removal mechanisms along with the key environmental parameters and operational conditions that enhance removal in subsurface flow wetland systems. The critical exploration identifies the major environmental parameters such as: pH, DO, and temperature, operational factors i.e. organic carbon availability, loading, feed mode, retention time, recirculation, harvesting, and the complex role (of both parameters) on classical nitrogen and organics removal pathways. Subsequently, the necessity of further extensive research on such factors, for promoting novel nitrogen removal routes in wetland systems has also been highlighted. The expansion of the review on the influence of the unconventional wetland matrix indicates that, the structural differences and inherent properties of these media can support substantial nitrogen and organics removal from wastewater, under optimal operating conditions. Overall, the critical review illustrates the necessity of a profound knowledge on the complicated inter-relationship between nitrogen and organics removal routes, governing environmental and operational parameters, and wetland matrix for improving the treatment performances of subsurface flow wetlands.
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The porous carbon with high specific surface area of 3001 m2/g and pore volume of 1.59 cm3/g using corncob was prepared for methane storage. The low and high pressure adsorption equilibria were tested using the prepared carbon. The... more
The porous carbon with high specific surface area of 3001 m2/g and pore volume of 1.59 cm3/g using corncob was prepared for methane storage. The low and high pressure adsorption equilibria were tested using the prepared carbon. The capacity of methane storage is evaluated using Tóth model with correction of fugacity using Benedict-Webb-Rubin equation of state in high pressure range. The theoretical maximum adsorption amount is achieved to be approximately 3.3 mmol/g. The adsorption process indicates physisorption dominates the adsorption with heterogeneous adsorption characteristic of sites on the surface of adsorbent at low pressure. The resultant carbon is ideal adsorbent for energy storage medium using methane.