Phosphorus removal from wastewater has been of growing interest for some decades to avoid eutrophication in surface water. In subsurface constructed wetlands precipitation and adsorption are the main mechanisms responsible of P uptake. The use of calcareous media is attractive because of p-ca interactions. Two media (calcite and recycled crushed concrete (rcc)) were examined in batch and continuous systems. They show attractive sorption capacities using batch experiments, however experiments carried out in open reactors pointed out some limitation in retention capacities and effluent quality. rcc was sensitive to a strong dissolution leading to a quick phosphorus precipitation but induced high conductivity and ph values in the treated water. Calcite efficiency depended on the material dissolution rate, directly linked to the carbonate equilibrium of the solution. Microscopic observations of the calcite surface show crystal making of phosphorus precipitate. Crystal growth seems to be the main P uptake once materials surfaces are covered. No experimental condition allows to reach an effluent concentration below 2 mgp.l-1.

Conçus initialement pour le traitement des eaux usées domestiques, les filtres plantés de roseaux ont été adaptés pour le traitement des effluents de lavage de salles de traite pour fournir une alternative au stockage et épandage. Pour simplifier les système en vue de réduire les coûts d'investissement, plusieurs sites expérimentaux ont été construits, modifiés si nécessaire et suivis. Placé à la suite d'une fosse toutes eaux de 3 à 9 m3, la configuration la plus aboutie consiste en 2 étages des filtres plantés à flux verticaux chacun étant composé de 2 filtres alimentés en alternance chaque semaine. La surface totale active correspond à 0.25m2 par vache laitière pour les eaux blanches seules (machine à traire et tank à lait) et 0.4m2 par vache lorsque s'y ajoutent les eaux vertes de lavage des quais et murs de la salle de traite. Les filtres du 1er étage occupent 65% de la surface totale. Observées dans 3 exploitations agricoles laitières, les concentrations obtenues atteignent une fourchette de 50 à 180 mg/L en DCO, 5 à 75 mg/L en DBO5 et 10 à 60 mg/L en MES. La nitrification qui est considérée comme un bon indicateur du potentiel d'oxydo-réduction dans le réacteur n'est certes pas complète mais beaucoup plus élevée que dans le cas de filtres à sable étudiés pour le même objectif alors que plusieurs d'entre eux ont colmaté. / Initially designed for the treatment of domestic wastewater, Vertical Flow Reed Bed Filters [VFRBF] have been adapted for washing parlour effluents to study the feasibility of the treatment of such effluents instead of their storage and land spreading. It was necessary to adapt the design of VFRBF to minimise the investment costs. Several experimental sites have been built, monitored and progressively adapted. Following a septic tank of 3 to 9 m3, the best design was considered to be: 2 stages of VFRBF in series each composed of 2 filters which are alternately fed on a weekly rhythm. The total active area is approximately equivalent to 0.25 m2 per milking cow for the washing effluent of the milking machine and milk-storage tank and 0.4 m2 per milking cow when the washing effluents from the floor and walls of the milking parlour are added to the previous ones. The 1st stage filters takes up 65 % of the total area. Based on a survey done in 3 farms, the concentrations achieved a range of 50 to 180 mgL-1 in COD, 5 to 75 mgL-1 in BOD5, 10 to 60 mgL-1 in SS. The nitrification, which can be considered as a good indicator of the redox potential within the filter media, was not complete but much more effective than in sand filters studied for the same purpose but some of them have clogged.

La législation française demande, depuis 1992, l'établissement de schémas directeurs pour le traitement et l'évacuation des eaux usées. Des zones d'assainissement collectif et des zones d'assainissement non collectif (autonome) doivent être définies. Les autorités locales peuvent, sous certaines conditions, choisir de prendre en charge la responsabilité du contrôle et de la gestion de ces installations privées d'assainissement non collectif. Il devrait progressivement en résulter une augmentation considérable des quantités de matières de vidange issues des fosses septiques qu'il faudra traiter. Les grosses stations d'épuration sont généralement équipées de cuves de dépotage des matières de vidanges extraites et transportées par camions citernes à dépression.. Néanmoins, dans certaines zones rurales la densité de telles installations n'est pas suffisante. Le Cemagref a été sollicité pour étudier, en modèle réduit dans un 1er temps, la faisabilité de stations adaptées et spécialement dédiées au traitement des matières de vidange. La station pilote expérimentale est composée de 2 étages : - s'appuyant sur l'expérience acquise en déshydratation des boues sur lits de séchage plantés de roseaux, le 1er étage a été conçu essentiellement pour retenir, par simple filtration, les concentrations élevées de matières en suspension des matières de vidange. Il apparaît toutefois qu'un important traitement biologique aérobie se produit également dans la couche drainante de gravier, connectée à l'atmosphère et aérée. Des abattements de 70 % sur la DCO dissoute, 79 % sur NK et 66 % concentrations en sels ammoniacaux ont été obtenues. - le 2ème étage est composé de 4 colonnes PVC (0.1 m²), chacune remplie de 15 cm de sable en surface et de quantité croissante de gravier sous-jacent : 0, 20, 40 et 60 cm. Il a notamment été montré que des concentrations plus faibles en DCO (environ 150 mg l-1) peuvent être obtenues et conjointement des concentrations plus faibles en sels ammoniacaux (< 1 mg l-1) avec la colonne remplie de 60 cm de gravier. La contribution de roseaux à améliorer le traitement biologique n'a pu être établie et au plan hydraulique, leur efficacité est discutable au sein d'une période couvrant moins d'un an après leur plantation. / Since 1992, French legislation requires the creation of master plans for evacuation and treatment of wastewater. Zones of collective and individual (on-site) treatment have to be defined. Local authorities may take responsibility for controlling and operating private on-site treatment systems. This will result in a considerable increase in the amount of sludge from septic tanks (faecal sludge : FS) that needs to be treated. Large wastewater treatment plants are able to treat such FS transported and removed with vacuum trucks. Nevertheless, in some rural areas, there are fewer of these plants. Cemagref has been asked to study the feasibility of treatment plants specially designed for treating FS. The pilot plant is made up of 2 stages : - the 1st stage is designed mainly to achieve filtration of the high concentrations of suspended solids in the FS. It also appears that an important aerobic biological treatment process occurs in the drainage gravel layer connected to the atmosphere. Removal rates of 70 % for soluble COD, 79 % for KN and 66 % for ammonia concentrations have been obtained. - the 2nd stage consists of 4 PVC columns (0.1m2), each filled with 15 cm of sand on top of 0, 20, 40 and 60 cm of gravel. COD concentrations around 150 mg 1-1 and low ammonia concentrations (< 1 mg 1-1) can be achieved with columns filled with 60 cm of gravel. The extent to which the reeds improve the biological treatment has not been established and from a hydraulic point of view, their effectiveness is debatable over a period of less than one year after being planted.

[Departement_IRSTEA]GMA [TR1_IRSTEA]21 - TECHNEAU / EPURE | International audience | Phosphorus removal from wastewater has been of growing interest for some decades to avoid eutrophication in surface water. In subsurface constructed wetlands precipitation and adsorption are the main mechanisms responsible of P uptake. The use of calcareous media is attractive because of p-ca interactions. Two media (calcite and recycled crushed concrete (rcc)) were examined in batch and continuous systems. They show attractive sorption capacities using batch experiments, however experiments carried out in open reactors pointed out some limitation in retention capacities and effluent quality. rcc was sensitive to a strong dissolution leading to a quick phosphorus precipitation but induced high conductivity and ph values in the treated water. Calcite efficiency depended on the material dissolution rate, directly linked to the carbonate equilibrium of the solution. Microscopic observations of the calcite surface show crystal making of phosphorus precipitate. Crystal growth seems to be the main P uptake once materials surfaces are covered. No experimental condition allows to reach an effluent concentration below 2 mgp.l-1.

Fifteen endophytic isolates were recovered from the phytoremediator plant Phragmites. Phylogenetic analysis revealed they were primarily from the class Sordariomycetes and Dothiodiomycetes. Most of the endophytes in Sordariomycetes were from the orders Diaporthales (six isolates, e.g., Diaporthe, Phomopsis), Hypocreales (two isolates, e.g., Gliomastix, Trichoderma), and Xylariales (one isolate, e.g., Arthrinium), while members from Dothideomycetes were from the order Pleosporales (six isolates, e.g., Bipolaris, Curvularia, Microsphaeropsis, Saccharicola). The endophytes demonstrated varying responses to the metals (Al³⁺, Cu²⁺, Zn²⁺, Pb²⁺, and Cd²⁺) and concentrations (10, 25, 50, 100, and 200 mg L⁻¹) tested, with isolates of Dothideomycetes predominantly more tolerable to metals (80–97% tolerance) than Sordariomycetes (73–90% tolerance). Pb²⁺ was the least harmful towards the endophytes, while Al³⁺ appeared to be highly toxic with mean tolerable range (TR) of > 200 and 25–50 mg L⁻¹, respectively. Endophytes thriving in toxic metals may further be applied for biocontrol, bioremediation, or growth-promoting purposes in metal-contaminated areas.

Constructed wetlands (CWs) and algae tanks are regarded as promising polishing steps to treat wastewaters for the removal of persistent organic pollutants, such as pharmaceuticals and personal care products (PPCPs). In this systematic review, we provide a synthesis of the relationship between the presence of the most widely studied PPCPs in domestic wastewater and the conformation of the CWs and algae tanks constructed to treat them. The six drugs most commonly found in the reviewed articles were caffeine, carbamazepine, diclofenac, ibuprofen, ketoprofen, and naproxen. Removal efficiency of the PPCPs was evaluated by means of the following selected parameters: hydraulic retention time (HRT), system flow rate, temperature, inflow concentration, and average removal rate. The average removal rate of PPCPs in CWs showed a positive and moderate relationship with the HRT (r = 0.346). A different flow configuration and plant species acted better for different target compounds. The average concentration reduction ranged from 80% for caffeine to zero reduction levels in some conformations for carbamazepine, diclofenac, and ketoprofen. There was a wide variation in the concentration reduction of different plant genera or unplanted tanks, ranging from 81% (caffeine using Phragmites sp.) to no reduction in an unplanted tank for diclofenac. The algae tanks were more efficient in removing most of the six target compounds than the wetlands. Removal rates ranged from 50% for ketoprofen to 16% for naproxen. According to our results, a combination of CW systems and algae tanks might be an effective alternative for the removal of PPCPs from domestic wastewater.

In this research, the role of plants in improving microorganism growth conditions in subsurface flow constructed wetland (CW) microcosms was determined. In particular, microbial abundance and community were investigated during summer and winter in Phragmites australis-planted CW microcosms (PA) and unplanted CW microcosms (control, CT). Results revealed that the removal efficiencies of pollutants and microbial community structure varied in winter with variable microbial abundance. During summer, PA comprised more dominant phyla (e.g., Proteobacteria, Actinobacteria, and Bacteroidetes), whereas CT contained more Cyanobacteria and photosynthetic bacteria. During winter, the abundance of Proteobacteria was >40 % in PA but dramatically decreased in CT. Moreover, Cyanobacteria and photosynthetic bacterial dominance in CT decreased. In both seasons, bacteria were more abundant in root surfaces than in sand. Plant presence positively affected microbial abundance and community. The potential removal ability of CT, in which Cyanobacteria and photosynthetic bacteria were abundant during summer, was more significantly affected by temperature reduction than that of PA with plant presence.

We aimed at assessing the effects of four wetland plant species commonly used in constructed wetland systems: Typha, Phragmites, Iris and Juncus for removing ibuprofen (IBU) and iohexol (IOH) from spiked culture solution and exploring the mechanisms responsible for the removal. IBU was nearly completely removed by all plant species during the 24-day experiment, whereas the IOH removal varied between 13 and 80 %. Typha and Phragmites were the most efficient in removing IBU and IOH, respectively, with first-order removal rate constants of 0.38 and 0.06 day⁻¹, respectively. The pharmaceuticals were taken up by the roots and translocated to the aerial tissues. However, at the end of the experiment, plant accumulation constituted only up to 1.1 and 5.7 % of the amount of IBU and IOH spiked initially. The data suggest that the plants mainly function by facilitating pharmaceutical degradation in the rhizosphere through release of root exudates.

This study investigates biomass, density, photosynthetic activity, and accumulation of nitrogen (N) and phosphorus (P) in three wetland plants (Canna indica, Typha augustifolia, and Phragmites austrail) in response to the introduction of the earthworm Eisenia fetida into a constructed wetland. The removal efficiency of N and P in constructed wetlands were also investigated. Results showed that the photosynthetic rate (P n), transpiration rate (T r), and stomatal conductance (S cond) of C. indica and P. austrail were (p < 0.05) significantly higher when earthworms were present. The addition of E. fetida increased the N uptake value by above-ground of C. indica, T. augustifolia, and P. australis by 185, 216, and 108 %, respectively; and its P uptake value increased by 300, 355, and 211 %, respectively. Earthworms could enhance photosynthetic activity, density, and biomass of wetland plants in constructed wetland, resulting in the higher N and P uptake. The addition of E. fetida into constructed wetland increased the removal efficiency of TN and TP by 10 and 7 %, respectively. The addition of earthworms into vertical flow constructed wetland increased the removal efficiency of TN and TP, which was related to higher photosynthetic activity and N and P uptake. The addition of earthworms into vertical flow constructed wetland and plant harvests could be the significantly sustainable N and P removal strategy.

Chromium (Cr), one of the most abundant and hazardous heavy metals, is generally observed to be widely distributed in environment, primarily due to the inter-mixing of the untreated domestic and industrial wastewaters. There has been an increased interest to replace conventional centralized treatment technologies with the low energy, low cost, and zero sludge producing decentralized constructed wetland technology. Therefore, a long-term investigation on the comparative metal removal efficiency of the experimental vertical sub-surface flow (VSSF) constructed wetland systems, irrigated with Cr-spiked ground waters, under both mono and mixed-culture conditions planted with five different macrophytes viz. Typha (T), Phragmites (P), Acorus (V), Arundo (A), and Vetiver (K), in as mono- and {viz. (TP), (PA), (KV), (AT), and (VT)} as co-cropped combinations along with unplanted (U) systems as controls was conducted at the ICAR-Indian Agricultural Research Institute, New Delhi, India. Long-term investigations revealed significant differences between metal removal efficiencies of the planted (61.6% to 78.5%) and the unplanted systems (32.8% to 47.9%). However, these long-term average metal removal efficiencies were found to be insignificantly different for the mono (78.5%) and the co-cropped systems (77.6%). On further compartmentalization of the experimental wetland system’s Cr-removal efficiencies amongst the major components viz. plant, microbe, and substrate, it was observed that vegetation contributed the maximum (i.e., 33–48%) while the microbes and the substrate contributed only 4–20% and 8–28%, respectively. It was further observed that due to reduced microbial diversity under unplanted conditions, the planted systems were associated with 2–7% higher microbial and equivalently lower substrate removal efficiencies. Thus, microbial activity-mediated metal mobilization and plant uptake were observed to be the principal processes governing Cr removal in the test VSSF constructed wetland systems exposed to varying Cr concentrations. Amongst all test macrophytes and their combinations, Arundo (81.9%) and Acorus (84.5%) based monocropped systems and Arundo+Typha (89.3%) based co-cropped systems emerged to be the most superior Cr-removing systems. Graphical abstarct