Florent Chazarenc - Academia.edu (original) (raw)

Papers by Florent Chazarenc

Ecological …, Oct 2, 2006

In horizontal subsurface flow constructed wetlands, oxygen availability, which is frequently low ... more In horizontal subsurface flow constructed wetlands, oxygen availability, which is frequently low in summer, may be even more limiting in winter when the plants are dormant. We tested the contribution of artificial aeration on pollutant removal in summer and winter, with a combination of planted, unplanted, aerated and non-aerated mesocosms treating a reconstituted fish farm effluent. Artificial aeration slightly enhanced TSS removal in all seasons regardless of treatment, probably by maintaining empty space in the head part of the gravel bed. In winter, the reduction in COD removal in non-aerated mesocosms compared to summer was totally compensated for in aerated mesocosms, in both planted and unplanted units. Artificial aeration improved summer and winter TKN removal for unplanted units, but the additional aeration did not fully compensate for the absence of plants, which suggests that the role of macrophytes goes beyond the sole addition of oxygen in the rhizosphere. Artificial aeration also improved TKN removal in planted units, but to a lower extent than for unplanted units. Our results suggest that artificial aeration represents a promising approach to improve removal efficiency in horizontal subsurface flow constructed wetland (HSSFCW), especially for fresh water fish farms in cold climate, where artificial aeration is readily available.

In treatment wetlands for domestic wastewater disposal, a considerable decrease in phosphorus rem... more In treatment wetlands for domestic wastewater disposal, a considerable decrease in phosphorus removal is generally observed after 3-4 years following the startup. Treatment wetlands performances have to be upgraded more and more often by directing durably discarded P according to requirements. The use of high P-capacity media was identified as a major issue over the last 10 years, and elevated P-sorption capacities of industrial by-products including steel-slag, iron-slag, oil-shale-ash and coal ash were recently highlighted. Besides updating the knowledge, this mini-review is aimed at critically evaluating the feasibility of using industrial by-products inside or downstream of treatment wetlands in terms of P-sorption capacities, mechanisms and limits. Most of the valuable available literature (46 articles in peer reviewed journals) has been incorporated. Recent advances were mainly considered as half of the articles were published over the last three years. In selected papers, inv...

Water Science & Technology, 2015

ABSTRACT

Ecological Engineering, 2015

ABSTRACT During the last two decades a couple of models were developed for constructed wetlands w... more ABSTRACT During the last two decades a couple of models were developed for constructed wetlands with differing purposes. Meanwhile the usage of this kind of tool is generally accepted, but the misuse of the models still confirms the skepticism. Generally some groups of models can be distinguished: on one hand mechanistic models try to display the complex and diffuse interaction of occurring processes, on the other hand the same kind of models are used to investigate single processes. New kinds of ‘simplified’ approaches – well appreciated by engineers – try to display system performances without going to deep into details. All types of models are valuable – some more for scientific usage, others more for engineering. The given summary tries to support potential users in taking the right choice in model selection. Big differences can be found in the model availabilities. Whereas some of the compared software packages are purchasable without limitation, some others are only accessible on their platform level, and some can be seen as exclusive property. From the experience of the authors it can be summarized, that research groups starting modelling/simulation studies should be encouraged to use the given knowledge before starting from scratch again.

International Journal of Chemical Engineering, 2010

Evapotranspiration (ET) in constructed wetlands (CWs) represents a major factor affecting hydrody... more Evapotranspiration (ET) in constructed wetlands (CWs) represents a major factor affecting hydrodynamics and treatment performances. The presence of high ET was shown to improve global treatment performances, however ET is affected by a wide range of parameters including plant development and CWs age. Our study aimed at modelling the effect of plants and peat on ET in CWs; since we hypothesized peat could behave like the presence of accumulated organic matter in old CWs. Treatment performances, hydraulic behaviour, and ET rates were measured in eight 1 m 2 CWs mesocosm (1 unplanted, 1 unplanted with peat, 2 planted with Phragmites australis, 2 planted with Typha latifolia and 2 planted with Phragmites australis with peat). Two models were built using first order kinetics to simulate COD and TKN removal with ET as an input. The effect of peat was positive on ET and was related to the better growth conditions it offered to macrophytes. Removal efficiency in pilot units with larger ET was higher for TKN. On average, results show for COD a k 20 value of 0.88 d −1 and 0.36 d −1 for TKN. We hypothesized that the main effect of ET was to concentrate effluent, thus enhancing degradation rates.

Asia-Pacific Journal of Chemical Engineering, 2014

ABSTRACT The present research investigates the uptake of phosphate ions from aqueous solutions us... more ABSTRACT The present research investigates the uptake of phosphate ions from aqueous solutions using acidified laterite (ALS), a by-product from the production of ferric aluminium sulfate using laterite. Phosphate adsorption experiments were performed in batch systems to determine the amount of phosphate adsorbed as a function of solution pH, adsorbent dosage and thermodynamic parameters per fixed P concentration. Kinetic studies were also carried out to study the effect of adsorbent particle sizes. The maximum removal capacity of ALS observed at pH 5 was 3.68 mg P g−1. It was found that as the adsorbent dosage increases, the equilibrium pH decreases, so an adsorbent dosage of 1.0 g L−1 of ALS was selected. Adsorption capacity (qm) calculated from the Langmuir isotherm was found to be 2.73 mg g−1. Kinetic experimental data were mathematically well described using the pseudo first-order model over the full range of the adsorbent particle size. The adsorption reactions were endothermic, and the process of adsorption was favoured at high temperature; the ΔG and ΔH values implied that the main adsorption mechanism of P onto ALS is physisorption. The desorption studies indicated the need to consider a NaOH 0.1 M solution as an optimal solution for practical regeneration applications. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Water Science & Technology, 2007

It is often assumed that planted wastewater treatment systems outperform unplanted ones, mainly b... more It is often assumed that planted wastewater treatment systems outperform unplanted ones, mainly because plants stimulate belowground microbial population. Yet, fundamental interactions between plants and associated microorganisms remain only partly understood. The aim of our project was to evaluate microbial density and activity associated to the rhizosphere of three plant species. Experimental set-up, in six replicates, consisted of four 1.8-L microcosms respectively planted in monoculture of Typha angustifolia, Phragmites australis, Phalaris arundinacea and unplanted control. Plants were grown for two months with 25 L m(-2) d(-1) of secondary effluent (in g m(-2) d(-1): 1.3 TSS, 7.5 COD, 1.0 TKN). Sampling of substrate, roots and interstitial water was made according to depth (0-10, 10-20 cm). Biofilm was extracted with 500 mL of a buffer solution. Microbial density was directly estimated by flow cytometry and indirectly by protein measurements. Biological activity was determined using respirometry assays, dehydrogenase and enzymatic activity measurements. Our results show that microbial density and activity are higher in the presence of plants, with significantly higher values associated with Phalaris arundinacea. Greater density of aerobic or facultative bacteria was present in planted microcosm, particularly on root surface, suggesting root oxygen release. Microbes were present on substrate and roots as an attached biofilm and abundance was correlated to root surface throughout depth. Plant species root morphology and development seem to be a key factor influencing microbial-plant interaction.

International Journal of Chemical Engineering, 2010

In constructed wetlands, microorganisms associated with plants are assumed to play a major role. ... more In constructed wetlands, microorganisms associated with plants are assumed to play a major role. A one-year survey was conducted in five vertical flow constructed wetland systems that had been operating from 2 months to 8 years in small French villages (100-500 People Equivalent) to provide a better understanding of microbiological activity. The objective of our study was to highlight the most important factor generating variability between microorganisms communities compared to treatment performances. Results of community level physiological profiling using Biolog Ecoplates were analyzed using principal component analysis. The greatest microbial activity was observed in the oldest wetland during summer. Profiles of fed and rest bed were differentiated by the nature of the main carbon source metabolized. Whereas carbohydrates and carboxylic acids appeared to be better assimilated with fed beds, it seemed that phosphate compounds as well as amines allowed better growth in the plates inoculated with samples of rest beds. In all fed beds, the most important parameters affecting the diversity were the season and the age of the wetlands. There were only slight profile differences between surface and subsurface samples and between the first and second stage samples.

Ecological Engineering, 2015

The main objective of our work was to study the efficiency of the 2 stages French vertical flow c... more The main objective of our work was to study the efficiency of the 2 stages French vertical flow constructed wetland system and its compact version by compiling data of 169 full scale systems in operation for up to 12 years. Design parameters and treatment performances, mostly based on 24 h composite samples performed by independent local authorities, have been compared to see how climate, wastewater composition, loading rates, system age and design were influencing the treatment performances. A bit more than 97% of the samples analysed at outlet of the plants were fulfilling the most common French discard limits (in mg/L 125 COD, 25 BOD). Removal efficiencies were not affected by factors including hydraulic and organic loads (until 60 cm/d), defect of maintenance and temperature within the ranges observed. Age of treatment plants had an effect only during start-up, but after 0.5-2 years of operation, performance was constant. Similarly, the feedback from 5 years of data obtained with "compact VFCWs" showed that this system met French standards and outperformed the first stage of "classical VFCWs". This survey of 169 full scale systems represents a confirmation of the good performance and the robustness of the French VFCWs.

Ecological Engineering, 2014

ABSTRACT

... Objectif 3 : Proposer une unité pour permettre de traiter la majorité du débit contenant envi... more ... Objectif 3 : Proposer une unité pour permettre de traiter la majorité du débit contenant environ 75 % du phosphore dissous par l'utilisation d'un lit fluidisé à particules absorbantes ... 2.1.1 Identification des créneaux d'utilisation des scories en traitement d'eaux usées ...

Water, Air, & Soil Pollution, 2010

Hydroponics culture generates large amounts of wastewater that are highly concentrated in nitrate... more Hydroponics culture generates large amounts of wastewater that are highly concentrated in nitrate and phosphorus but contains almost no organic carbon. Constructed wetlands (CWs) have been proposed to treat this type of effluent, but little is known about the performance of these systems in treating hydroponic wastewater. In addition, obtaining satisfactory winter performances from CWs operated in cold climates remains a challenge, as biological pathways are often slowed down or inhibited. The main objective of this study was to assess the effect of plant species (Typha sp., Phragmites australis, and Phalaris arundinacea) and the addition of organic carbon on nutrient removal in winter. The experimental setup consisted of 16 subsurface flow CW mesocosms (1 m 2 , HRT of 3 days) fed with 30 Ld 1 of synthetic hydroponics wastewater, with half of the mesocosms fed with an additional source of organic carbon (sucrose). Carbon addition had a significant impact on nitrate and phosphate removal, with removal means of 4.9 g m -2 d -1 of NO 3 -N and 0.5 g m -2 d -1 of PO 4 -P. Planted mesocosms were generally more efficient than unplanted controls. Furthermore, we found significant differences among plant treatments for NO 3 -N (highest removal with P. arundinacea) and COD (highest removal with P. australis/Typha sp.). Overall, planted wetlands with added organic carbon represent the best combination to treat hydroponics wastewater during the winter.

Water, Air, & Soil Pollution, 2012

... Cu, Ni, Pb, and Zn as a function of pH was performed using a computer ... Arsenic concentrati... more ... Cu, Ni, Pb, and Zn as a function of pH was performed using a computer ... Arsenic concentration in sediments corresponded to the geopedochemical background, defined as arsenic concentration in ... 4.3 The Use of Aquatic Plants as Bioindicators of Aquatic Heavy Metal Pollution ...

Water, Air, & Soil Pollution, 2013

ABSTRACT Conventional stormwater detention ponds frequently show limitations for dissolved heavy ... more ABSTRACT Conventional stormwater detention ponds frequently show limitations for dissolved heavy metal removal. Floating treatment wetlands (FTWs), a variant of constructed wetlands, are considered as a promising technology to improve the quality of urban stormwater runoff. Our study aimed at evaluating the treatment performances of FTWs for cadmium, nickel, and zinc removal through a pot experiment. Two macrophytes species, Juncus effusus and Carex riparia, were grown during 4 months under three metal concentrations (in micrograms per liter): high (Cd, 200; Ni, 500; Zn, 2,000), low (Cd, 10; Ni, 10; Zn, 40), and control (Cd–Ni–Zn, 0). Results showed that both macrophytes species significantly removed dissolved heavy metals. Cadmium and nickel accumulations were greater in roots than in shoots for both species. Under low metal concentration, maximum accumulation of 0.4 μg g−1 dry weight (DW) for Cd was observed in the roots of J. effusus. Under high metal concentration, accumulations of up to 5 μg Cd g−1 DW and 62 μg Ni g−1 DW were observed in the roots of J. effusus and up to 73 μg Zn g−1 DW in the roots of C. riparia. Although J. effusus and C. riparia are not recognized as metal hyperaccumulators, our study demonstrated that they can achieve high metal uptake when both roots and shoots are harvested.

Water Science & Technology, 2013

Upgrades to enhance nitrogen removal were tested in a 2 year old pilot vertical flow constructed ... more Upgrades to enhance nitrogen removal were tested in a 2 year old pilot vertical flow constructed wetland in spring and summer periods. The effects of a saturated layer and of recirculation were tested in particular. Two pilots (L ¼ 2 m, W ¼ 1.25 m, H ¼ 1.2 m), filled with expanded schist (Mayennite ® ), were designed with hydraulic saturated layers of 20 and 40 cm at the bottom. Each pilot was fed with raw domestic wastewater under field conditions according to a hydraulic load of 15-38 cm d À1 (i.e. 158-401 g COD (chemical oxygen demand) m À2 d À1 ) and to recirculation rates ranging from 0% up to 150%. The initial load during the first 2 years of operation resulted in an incomplete mineralized accumulated sludge leading to total suspended solids (TSS), COD and biochemical oxygen demand (BOD 5 ) release. A 40 cm hydraulic saturated layer enabled an increase of 5-10% total nitrogen (TN) removal compared to a 20 cm saturated layer. Recirculation allowed the dilution of raw wastewater and enhanced nitrification in a single stage. A design of 1.8 m² pe À1 (48 cm d À1 , 191 g COD m À2 d À1 ) with a 40 cm saturated layer and 100% recirculation enabled the French standard D4 (35 mg TSS L À1 , 125 mg COD L À1 , 25 mg BOD 5 L À1 ), nitrogen concentrations below 20 mg TKN (total Kjeldahl nitrogen) L À1 and 50 mg TN L À1 , to be met.

Water Science & Technology, 2007

Tracer studies performed in two aerated facultative lagoons indicate some bypass and an overall h... more Tracer studies performed in two aerated facultative lagoons indicate some bypass and an overall hydraulic regime close to completely-mixed. Results were used to calibrate a hydraulic model based on the tanks-in-series approach. The hydraulic model was combined with a simple "death-regeneration" biokinetic model to simulate seasonal nitrification as observed over a three year period. Modifications were made to the hydraulic model to represent the effect of baffle installations to 1) eliminate bypass and 2) impose a plug-flow regime. Simulation results indicate there is some gain to eliminating bypass but that imposing a plug-flow regime would increase biomass washout rates and hinder nitrification.

Water Science & Technology, 2007

The effect of organic loading, season and plant species on the treatment of fish farm effluent wa... more The effect of organic loading, season and plant species on the treatment of fish farm effluent was tested using three-year old mesocosm wetland systems. During one year, nine 1 m 2 mesocosms (horizontal subsurface flow), located in a controlled greenhouse environment, were fed with a reconstituted fish farm effluent containing a high fraction of soluble components (1,600 mS/cm and in mg/L: 230^80 COD, 179^60 sCOD, 100^40 TSS, 37^7 TKN, 14^2 TP). Combinations of three hydraulic loading rates (30, 60 and 90 L.m 22 d 21 ) and two plant species (Phragmites australis, Typha angustifolia) and an unplanted control were tested for treatment performance and hydraulic behaviour. Loadings higher than 15 g COD m 22 d 21 resulted in a net decrease of hydraulic performances (generation of short circuiting) coupled with low TKN removal. Maximal TKN removal rates (summer: 1.2, winter: 0.6 g.m 22 d 21 ) were reached in planted units. In all mesocosms, phosphorus was removed during summer (maximal removal rate: 0.3 g TP m 22 d 21 ) and was released in winter (release rate ¼ , half of summer removal rate). This study confirmed that constructed wetlands are susceptible to clogging when treating anaerobic storage tank supernatant rich in highly biodegradable compounds. Contributions of plants to hydraulic efficiency were mainly observed in summer, associated with high evapotranspiration rates. Both plant species gave a similar removal efficiency for all pollutants.

Water Science & Technology, 2007

The current best option to upgrade constructed wetlands (CWs) for phosphorus (P) retention, in te... more The current best option to upgrade constructed wetlands (CWs) for phosphorus (P) retention, in terms of efficiency, cost and simplicity, consists in using media having a strong P affinity. The media can be used either in the planted beds or in a filtration system downstream of the beds. The use of slag filters was shown to be efficient for removing P from wastewater as it represented a slow release source of calcium and hydroxide, favouring the formation of hydroxyapatite. Our study aimed at maximising the P retention capacity of slag filters located at the outlet of CWs since electric arc furnace slag has been shown to inhibit the growth of macrophytes when used in the filtration matrix. Bench-scale columns (Vtot = 6.2 L) filled with various combinations of filter media (slag, granite, limestone) of different sizes (2-5, 5-10, 10-20 mm) were fed on-site during four months with a CW effluent (in mg/L: 30 COD, 30 TSS, 10 Pt). Results showed that the best media combination enabling the maximum o-PO4 retention (more than 80% removal without clogging) consisted in a series of a ternary mix column (slag 5-10 mm, granite 2-5 mm, limestone 5-10 mm) followed by a slag column (slag 5-10 mm). Pilot scale columns (Vtot = 300 L), filled with the best media combination, were installed at the outlet of a 28 m2 CW. These columns showed more than 75% removal efficiency during one year and were designed to be easily replaced each year.

Water Research, 2012

Sludge treatment wetlands are mainly used to reduce the volume of activated sludge, and the pollu... more Sludge treatment wetlands are mainly used to reduce the volume of activated sludge, and the pollutants at the outlet are generally returned to the wastewater treatment plant. However, in cases where sludges are produced far from treatment plants not only must the sludge be treated, but the discharge of pollutants into the surrounding environment must also be limited. The aim of this study was to evaluate the efficiency of different plant species in optimising pollutant removal in a decentralised sludge treatment wetland. In addition, a new system design was assessed, in which the wetland was not completely drained, and a saturated layer was created using an overflow. The experimental setup consisted of 16 mesocosms in total, planted with monocultures of Phragmites australis, Typha angustifolia and Scirpus fluviatilis, and unplanted controls, each in four replicates. The experiment was conducted during the third summer of operation after setup. The system was fed with highly concentrated fish farm sludge at a load of 30 kg of total solids m(-2) yr(-1). Results showed that such wetlands were highly efficient, with removal rates between 94% and 99% for most pollutants. Planted systems generally outperformed the unplanted control, with a significantly lower mass of pollutants at the outlet of the sludge treatment wetland planted with Phragmites, followed by those with Typha and then Scirpus. The distinct influence of plant species on pollution removal was explained by the sequestration of nitrogen and phosphorus in plant tissues and by the rhizosphere effect, which enhance the biodegradation of organic matter, allowed the nitrification process and created redox conditions favourable to the sorption of phosphorus. Filtration and evapotranspiration rates played a major role in limiting the discharge of pollutants, and the impact was enhanced by the fact that the sludge treatment wetland was not completely drained.

Ecological …, Oct 2, 2006

In horizontal subsurface flow constructed wetlands, oxygen availability, which is frequently low ... more In horizontal subsurface flow constructed wetlands, oxygen availability, which is frequently low in summer, may be even more limiting in winter when the plants are dormant. We tested the contribution of artificial aeration on pollutant removal in summer and winter, with a combination of planted, unplanted, aerated and non-aerated mesocosms treating a reconstituted fish farm effluent. Artificial aeration slightly enhanced TSS removal in all seasons regardless of treatment, probably by maintaining empty space in the head part of the gravel bed. In winter, the reduction in COD removal in non-aerated mesocosms compared to summer was totally compensated for in aerated mesocosms, in both planted and unplanted units. Artificial aeration improved summer and winter TKN removal for unplanted units, but the additional aeration did not fully compensate for the absence of plants, which suggests that the role of macrophytes goes beyond the sole addition of oxygen in the rhizosphere. Artificial aeration also improved TKN removal in planted units, but to a lower extent than for unplanted units. Our results suggest that artificial aeration represents a promising approach to improve removal efficiency in horizontal subsurface flow constructed wetland (HSSFCW), especially for fresh water fish farms in cold climate, where artificial aeration is readily available.

In treatment wetlands for domestic wastewater disposal, a considerable decrease in phosphorus rem... more In treatment wetlands for domestic wastewater disposal, a considerable decrease in phosphorus removal is generally observed after 3-4 years following the startup. Treatment wetlands performances have to be upgraded more and more often by directing durably discarded P according to requirements. The use of high P-capacity media was identified as a major issue over the last 10 years, and elevated P-sorption capacities of industrial by-products including steel-slag, iron-slag, oil-shale-ash and coal ash were recently highlighted. Besides updating the knowledge, this mini-review is aimed at critically evaluating the feasibility of using industrial by-products inside or downstream of treatment wetlands in terms of P-sorption capacities, mechanisms and limits. Most of the valuable available literature (46 articles in peer reviewed journals) has been incorporated. Recent advances were mainly considered as half of the articles were published over the last three years. In selected papers, inv...

Water Science & Technology, 2015

ABSTRACT

Ecological Engineering, 2015

ABSTRACT During the last two decades a couple of models were developed for constructed wetlands w... more ABSTRACT During the last two decades a couple of models were developed for constructed wetlands with differing purposes. Meanwhile the usage of this kind of tool is generally accepted, but the misuse of the models still confirms the skepticism. Generally some groups of models can be distinguished: on one hand mechanistic models try to display the complex and diffuse interaction of occurring processes, on the other hand the same kind of models are used to investigate single processes. New kinds of ‘simplified’ approaches – well appreciated by engineers – try to display system performances without going to deep into details. All types of models are valuable – some more for scientific usage, others more for engineering. The given summary tries to support potential users in taking the right choice in model selection. Big differences can be found in the model availabilities. Whereas some of the compared software packages are purchasable without limitation, some others are only accessible on their platform level, and some can be seen as exclusive property. From the experience of the authors it can be summarized, that research groups starting modelling/simulation studies should be encouraged to use the given knowledge before starting from scratch again.

International Journal of Chemical Engineering, 2010

Evapotranspiration (ET) in constructed wetlands (CWs) represents a major factor affecting hydrody... more Evapotranspiration (ET) in constructed wetlands (CWs) represents a major factor affecting hydrodynamics and treatment performances. The presence of high ET was shown to improve global treatment performances, however ET is affected by a wide range of parameters including plant development and CWs age. Our study aimed at modelling the effect of plants and peat on ET in CWs; since we hypothesized peat could behave like the presence of accumulated organic matter in old CWs. Treatment performances, hydraulic behaviour, and ET rates were measured in eight 1 m 2 CWs mesocosm (1 unplanted, 1 unplanted with peat, 2 planted with Phragmites australis, 2 planted with Typha latifolia and 2 planted with Phragmites australis with peat). Two models were built using first order kinetics to simulate COD and TKN removal with ET as an input. The effect of peat was positive on ET and was related to the better growth conditions it offered to macrophytes. Removal efficiency in pilot units with larger ET was higher for TKN. On average, results show for COD a k 20 value of 0.88 d −1 and 0.36 d −1 for TKN. We hypothesized that the main effect of ET was to concentrate effluent, thus enhancing degradation rates.

Asia-Pacific Journal of Chemical Engineering, 2014

ABSTRACT The present research investigates the uptake of phosphate ions from aqueous solutions us... more ABSTRACT The present research investigates the uptake of phosphate ions from aqueous solutions using acidified laterite (ALS), a by-product from the production of ferric aluminium sulfate using laterite. Phosphate adsorption experiments were performed in batch systems to determine the amount of phosphate adsorbed as a function of solution pH, adsorbent dosage and thermodynamic parameters per fixed P concentration. Kinetic studies were also carried out to study the effect of adsorbent particle sizes. The maximum removal capacity of ALS observed at pH 5 was 3.68 mg P g−1. It was found that as the adsorbent dosage increases, the equilibrium pH decreases, so an adsorbent dosage of 1.0 g L−1 of ALS was selected. Adsorption capacity (qm) calculated from the Langmuir isotherm was found to be 2.73 mg g−1. Kinetic experimental data were mathematically well described using the pseudo first-order model over the full range of the adsorbent particle size. The adsorption reactions were endothermic, and the process of adsorption was favoured at high temperature; the ΔG and ΔH values implied that the main adsorption mechanism of P onto ALS is physisorption. The desorption studies indicated the need to consider a NaOH 0.1 M solution as an optimal solution for practical regeneration applications. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Water Science & Technology, 2007

It is often assumed that planted wastewater treatment systems outperform unplanted ones, mainly b... more It is often assumed that planted wastewater treatment systems outperform unplanted ones, mainly because plants stimulate belowground microbial population. Yet, fundamental interactions between plants and associated microorganisms remain only partly understood. The aim of our project was to evaluate microbial density and activity associated to the rhizosphere of three plant species. Experimental set-up, in six replicates, consisted of four 1.8-L microcosms respectively planted in monoculture of Typha angustifolia, Phragmites australis, Phalaris arundinacea and unplanted control. Plants were grown for two months with 25 L m(-2) d(-1) of secondary effluent (in g m(-2) d(-1): 1.3 TSS, 7.5 COD, 1.0 TKN). Sampling of substrate, roots and interstitial water was made according to depth (0-10, 10-20 cm). Biofilm was extracted with 500 mL of a buffer solution. Microbial density was directly estimated by flow cytometry and indirectly by protein measurements. Biological activity was determined using respirometry assays, dehydrogenase and enzymatic activity measurements. Our results show that microbial density and activity are higher in the presence of plants, with significantly higher values associated with Phalaris arundinacea. Greater density of aerobic or facultative bacteria was present in planted microcosm, particularly on root surface, suggesting root oxygen release. Microbes were present on substrate and roots as an attached biofilm and abundance was correlated to root surface throughout depth. Plant species root morphology and development seem to be a key factor influencing microbial-plant interaction.

International Journal of Chemical Engineering, 2010

In constructed wetlands, microorganisms associated with plants are assumed to play a major role. ... more In constructed wetlands, microorganisms associated with plants are assumed to play a major role. A one-year survey was conducted in five vertical flow constructed wetland systems that had been operating from 2 months to 8 years in small French villages (100-500 People Equivalent) to provide a better understanding of microbiological activity. The objective of our study was to highlight the most important factor generating variability between microorganisms communities compared to treatment performances. Results of community level physiological profiling using Biolog Ecoplates were analyzed using principal component analysis. The greatest microbial activity was observed in the oldest wetland during summer. Profiles of fed and rest bed were differentiated by the nature of the main carbon source metabolized. Whereas carbohydrates and carboxylic acids appeared to be better assimilated with fed beds, it seemed that phosphate compounds as well as amines allowed better growth in the plates inoculated with samples of rest beds. In all fed beds, the most important parameters affecting the diversity were the season and the age of the wetlands. There were only slight profile differences between surface and subsurface samples and between the first and second stage samples.

Ecological Engineering, 2015

The main objective of our work was to study the efficiency of the 2 stages French vertical flow c... more The main objective of our work was to study the efficiency of the 2 stages French vertical flow constructed wetland system and its compact version by compiling data of 169 full scale systems in operation for up to 12 years. Design parameters and treatment performances, mostly based on 24 h composite samples performed by independent local authorities, have been compared to see how climate, wastewater composition, loading rates, system age and design were influencing the treatment performances. A bit more than 97% of the samples analysed at outlet of the plants were fulfilling the most common French discard limits (in mg/L 125 COD, 25 BOD). Removal efficiencies were not affected by factors including hydraulic and organic loads (until 60 cm/d), defect of maintenance and temperature within the ranges observed. Age of treatment plants had an effect only during start-up, but after 0.5-2 years of operation, performance was constant. Similarly, the feedback from 5 years of data obtained with "compact VFCWs" showed that this system met French standards and outperformed the first stage of "classical VFCWs". This survey of 169 full scale systems represents a confirmation of the good performance and the robustness of the French VFCWs.

Ecological Engineering, 2014

ABSTRACT

... Objectif 3 : Proposer une unité pour permettre de traiter la majorité du débit contenant envi... more ... Objectif 3 : Proposer une unité pour permettre de traiter la majorité du débit contenant environ 75 % du phosphore dissous par l'utilisation d'un lit fluidisé à particules absorbantes ... 2.1.1 Identification des créneaux d'utilisation des scories en traitement d'eaux usées ...

Water, Air, & Soil Pollution, 2010

Hydroponics culture generates large amounts of wastewater that are highly concentrated in nitrate... more Hydroponics culture generates large amounts of wastewater that are highly concentrated in nitrate and phosphorus but contains almost no organic carbon. Constructed wetlands (CWs) have been proposed to treat this type of effluent, but little is known about the performance of these systems in treating hydroponic wastewater. In addition, obtaining satisfactory winter performances from CWs operated in cold climates remains a challenge, as biological pathways are often slowed down or inhibited. The main objective of this study was to assess the effect of plant species (Typha sp., Phragmites australis, and Phalaris arundinacea) and the addition of organic carbon on nutrient removal in winter. The experimental setup consisted of 16 subsurface flow CW mesocosms (1 m 2 , HRT of 3 days) fed with 30 Ld 1 of synthetic hydroponics wastewater, with half of the mesocosms fed with an additional source of organic carbon (sucrose). Carbon addition had a significant impact on nitrate and phosphate removal, with removal means of 4.9 g m -2 d -1 of NO 3 -N and 0.5 g m -2 d -1 of PO 4 -P. Planted mesocosms were generally more efficient than unplanted controls. Furthermore, we found significant differences among plant treatments for NO 3 -N (highest removal with P. arundinacea) and COD (highest removal with P. australis/Typha sp.). Overall, planted wetlands with added organic carbon represent the best combination to treat hydroponics wastewater during the winter.

Water, Air, & Soil Pollution, 2012

... Cu, Ni, Pb, and Zn as a function of pH was performed using a computer ... Arsenic concentrati... more ... Cu, Ni, Pb, and Zn as a function of pH was performed using a computer ... Arsenic concentration in sediments corresponded to the geopedochemical background, defined as arsenic concentration in ... 4.3 The Use of Aquatic Plants as Bioindicators of Aquatic Heavy Metal Pollution ...

Water, Air, & Soil Pollution, 2013

ABSTRACT Conventional stormwater detention ponds frequently show limitations for dissolved heavy ... more ABSTRACT Conventional stormwater detention ponds frequently show limitations for dissolved heavy metal removal. Floating treatment wetlands (FTWs), a variant of constructed wetlands, are considered as a promising technology to improve the quality of urban stormwater runoff. Our study aimed at evaluating the treatment performances of FTWs for cadmium, nickel, and zinc removal through a pot experiment. Two macrophytes species, Juncus effusus and Carex riparia, were grown during 4 months under three metal concentrations (in micrograms per liter): high (Cd, 200; Ni, 500; Zn, 2,000), low (Cd, 10; Ni, 10; Zn, 40), and control (Cd–Ni–Zn, 0). Results showed that both macrophytes species significantly removed dissolved heavy metals. Cadmium and nickel accumulations were greater in roots than in shoots for both species. Under low metal concentration, maximum accumulation of 0.4 μg g−1 dry weight (DW) for Cd was observed in the roots of J. effusus. Under high metal concentration, accumulations of up to 5 μg Cd g−1 DW and 62 μg Ni g−1 DW were observed in the roots of J. effusus and up to 73 μg Zn g−1 DW in the roots of C. riparia. Although J. effusus and C. riparia are not recognized as metal hyperaccumulators, our study demonstrated that they can achieve high metal uptake when both roots and shoots are harvested.

Water Science & Technology, 2013

Upgrades to enhance nitrogen removal were tested in a 2 year old pilot vertical flow constructed ... more Upgrades to enhance nitrogen removal were tested in a 2 year old pilot vertical flow constructed wetland in spring and summer periods. The effects of a saturated layer and of recirculation were tested in particular. Two pilots (L ¼ 2 m, W ¼ 1.25 m, H ¼ 1.2 m), filled with expanded schist (Mayennite ® ), were designed with hydraulic saturated layers of 20 and 40 cm at the bottom. Each pilot was fed with raw domestic wastewater under field conditions according to a hydraulic load of 15-38 cm d À1 (i.e. 158-401 g COD (chemical oxygen demand) m À2 d À1 ) and to recirculation rates ranging from 0% up to 150%. The initial load during the first 2 years of operation resulted in an incomplete mineralized accumulated sludge leading to total suspended solids (TSS), COD and biochemical oxygen demand (BOD 5 ) release. A 40 cm hydraulic saturated layer enabled an increase of 5-10% total nitrogen (TN) removal compared to a 20 cm saturated layer. Recirculation allowed the dilution of raw wastewater and enhanced nitrification in a single stage. A design of 1.8 m² pe À1 (48 cm d À1 , 191 g COD m À2 d À1 ) with a 40 cm saturated layer and 100% recirculation enabled the French standard D4 (35 mg TSS L À1 , 125 mg COD L À1 , 25 mg BOD 5 L À1 ), nitrogen concentrations below 20 mg TKN (total Kjeldahl nitrogen) L À1 and 50 mg TN L À1 , to be met.

Water Science & Technology, 2007

Tracer studies performed in two aerated facultative lagoons indicate some bypass and an overall h... more Tracer studies performed in two aerated facultative lagoons indicate some bypass and an overall hydraulic regime close to completely-mixed. Results were used to calibrate a hydraulic model based on the tanks-in-series approach. The hydraulic model was combined with a simple "death-regeneration" biokinetic model to simulate seasonal nitrification as observed over a three year period. Modifications were made to the hydraulic model to represent the effect of baffle installations to 1) eliminate bypass and 2) impose a plug-flow regime. Simulation results indicate there is some gain to eliminating bypass but that imposing a plug-flow regime would increase biomass washout rates and hinder nitrification.

Water Science & Technology, 2007

The effect of organic loading, season and plant species on the treatment of fish farm effluent wa... more The effect of organic loading, season and plant species on the treatment of fish farm effluent was tested using three-year old mesocosm wetland systems. During one year, nine 1 m 2 mesocosms (horizontal subsurface flow), located in a controlled greenhouse environment, were fed with a reconstituted fish farm effluent containing a high fraction of soluble components (1,600 mS/cm and in mg/L: 230^80 COD, 179^60 sCOD, 100^40 TSS, 37^7 TKN, 14^2 TP). Combinations of three hydraulic loading rates (30, 60 and 90 L.m 22 d 21 ) and two plant species (Phragmites australis, Typha angustifolia) and an unplanted control were tested for treatment performance and hydraulic behaviour. Loadings higher than 15 g COD m 22 d 21 resulted in a net decrease of hydraulic performances (generation of short circuiting) coupled with low TKN removal. Maximal TKN removal rates (summer: 1.2, winter: 0.6 g.m 22 d 21 ) were reached in planted units. In all mesocosms, phosphorus was removed during summer (maximal removal rate: 0.3 g TP m 22 d 21 ) and was released in winter (release rate ¼ , half of summer removal rate). This study confirmed that constructed wetlands are susceptible to clogging when treating anaerobic storage tank supernatant rich in highly biodegradable compounds. Contributions of plants to hydraulic efficiency were mainly observed in summer, associated with high evapotranspiration rates. Both plant species gave a similar removal efficiency for all pollutants.

Water Science & Technology, 2007

The current best option to upgrade constructed wetlands (CWs) for phosphorus (P) retention, in te... more The current best option to upgrade constructed wetlands (CWs) for phosphorus (P) retention, in terms of efficiency, cost and simplicity, consists in using media having a strong P affinity. The media can be used either in the planted beds or in a filtration system downstream of the beds. The use of slag filters was shown to be efficient for removing P from wastewater as it represented a slow release source of calcium and hydroxide, favouring the formation of hydroxyapatite. Our study aimed at maximising the P retention capacity of slag filters located at the outlet of CWs since electric arc furnace slag has been shown to inhibit the growth of macrophytes when used in the filtration matrix. Bench-scale columns (Vtot = 6.2 L) filled with various combinations of filter media (slag, granite, limestone) of different sizes (2-5, 5-10, 10-20 mm) were fed on-site during four months with a CW effluent (in mg/L: 30 COD, 30 TSS, 10 Pt). Results showed that the best media combination enabling the maximum o-PO4 retention (more than 80% removal without clogging) consisted in a series of a ternary mix column (slag 5-10 mm, granite 2-5 mm, limestone 5-10 mm) followed by a slag column (slag 5-10 mm). Pilot scale columns (Vtot = 300 L), filled with the best media combination, were installed at the outlet of a 28 m2 CW. These columns showed more than 75% removal efficiency during one year and were designed to be easily replaced each year.

Water Research, 2012

Sludge treatment wetlands are mainly used to reduce the volume of activated sludge, and the pollu... more Sludge treatment wetlands are mainly used to reduce the volume of activated sludge, and the pollutants at the outlet are generally returned to the wastewater treatment plant. However, in cases where sludges are produced far from treatment plants not only must the sludge be treated, but the discharge of pollutants into the surrounding environment must also be limited. The aim of this study was to evaluate the efficiency of different plant species in optimising pollutant removal in a decentralised sludge treatment wetland. In addition, a new system design was assessed, in which the wetland was not completely drained, and a saturated layer was created using an overflow. The experimental setup consisted of 16 mesocosms in total, planted with monocultures of Phragmites australis, Typha angustifolia and Scirpus fluviatilis, and unplanted controls, each in four replicates. The experiment was conducted during the third summer of operation after setup. The system was fed with highly concentrated fish farm sludge at a load of 30 kg of total solids m(-2) yr(-1). Results showed that such wetlands were highly efficient, with removal rates between 94% and 99% for most pollutants. Planted systems generally outperformed the unplanted control, with a significantly lower mass of pollutants at the outlet of the sludge treatment wetland planted with Phragmites, followed by those with Typha and then Scirpus. The distinct influence of plant species on pollution removal was explained by the sequestration of nitrogen and phosphorus in plant tissues and by the rhizosphere effect, which enhance the biodegradation of organic matter, allowed the nitrification process and created redox conditions favourable to the sorption of phosphorus. Filtration and evapotranspiration rates played a major role in limiting the discharge of pollutants, and the impact was enhanced by the fact that the sludge treatment wetland was not completely drained.