Surface Flow Constructed Wetlands Research Articles

Removal of antibiotics and antibiotic resistance genes from domestic sewage by constructed wetlands: Effect of flow configuration and plant species

This study aims to investigate the removal of antibiotics and antibiotic resistance genes (ARGs) in raw domestic wastewater by various mesocosm-scale constructed wetlands (CWs) with different flow configurations or plant species including the constructed wetland with or without plant. Six mesocosm-scale CWs with three flow types (surface flow, horizontal subsurface flow and vertical subsurface flow) and two plant species (Thaliadealbata Fraser and Iris tectorum Maxim) were set up in the outdoor. 8 antibiotics including erythromycin-H2O (ETM-H2O), monensin (MON), clarithromycin (CTM), leucomycin (LCM), sulfamethoxazole (SMX), trimethoprim (TMP), sulfamethazine (SMZ) and sulfapyridine (SPD) and 12 genes including three sulfonamide resistance genes (sul1, sul2 and sul3), four tetracycline resistance genes (tetG, tetM, tetO and tetX), two macrolide resistance genes (ermB and ermC), two chloramphenicol resistance genes (cmlA and floR) and 16S rRNA (bacteria) were determined in different matrices (water, particle, substrate and plant phases) from the mesocosm-scale systems. The aqueous removal efficiencies of total antibiotics ranged from 75.8 to 98.6%, while those of total ARGs varied between 63.9 and 84.0% by the mesocosm-scale CWs. The presence of plants was beneficial to the removal of pollutants, and the subsurface flow CWs had higher pollutant removal than the surface flow CWs, especially for antibiotics. According to the mass balance analysis, the masses of all detected antibiotics during the operation period were 247,000, 4920–10,600, 0.05–0.41 and 3500–60,000μg in influent, substrate, plant and effluent of the mesocosm-scale CWs. In the CWs, biodegradation, substrate adsorption and plant uptake all played certain roles in reducing the loadings of nutrients, antibiotics and ARGs, but biodegradation was the most important process in the removal of these pollutants.

Removal Behavior of Ibuprofen and Diclofenac in Different Constructed Wetlands

Ibuprofen and diclofenac, two commonly used pharmaceuticals, were studied to evaluate the removal behavior of acid pharmaceuticals in constructed wetlands (CWs) with different flow types, vegetation and seasons. It was shown that flow types influenced the results significantly. The average removal efficiency of ibuprofen in horizontal subsurface flow (HSSF) and vertical subsurface flow (VSSF) CWs (69% and 60%, respectively) was significantly higher than that in surface flow (SF) CWs (26%). For diclofenac, SF CWs (58%) was significantly higher than HSSF and VSSF CWs (49% and 43%, respectively). In addition, the presence of plants improved the efficiency of ibuprofen, while it had no significant influence on the removal of diclofenac. Paired t-test found out that summer and autumn season variety had little impact on the removal. Furthermore, the removal of diclofenac and DO, as well as COD, showed very significant negative correlations. Opposite to diclofenac, the removal of ibuprofen had good positive correlations with dehydrogenase activities. The research indicated that aerobic biodegradation behavior mainly took place in ibuprofen, yet anaerobic biodegradation and photolysis behavior were expected for diclofenac.

Effect of photosynthetically elevated pH on performance of surface flow-constructed wetland planted with Phragmites australis

Combination of emergent and submerged plants has been proved to be able to enhance pollutant removal efficiency of surface flow-constructed wetland (SFCW) during winter. However, intensive photosynthesis of submerged plants during summer would cause pH increase, which may have adverse effects on emergent plants. In this study, nitrogen transformation of lab-scale SFCW under pH gradient of 7.5, 8.5, 9.5 and 10.5 was systematically investigated. The results showed that total nitrogen (TN) removal efficiency decreased from 76.3 ± 0.04 to 51.8 ± 0.04% when pH increased from 7.5 to 10.5, which was mainly attributed to plant assimilation decay and inhibition of microbe activities (i.e., nitrite-oxidizing bacteria and denitrifiers). Besides, the highest sediment adsorption in SFCW was observed at pH of 8.5. In general, the combination of submerged and emergent plants is feasible for most of the year, but precaution should be taken to mitigate the negative effect of high alkaline conditions when pH rises to above 8.5 in midsummer.

Carbon and nitrogen dynamics and greenhouse gas emissions in constructed wetlands treating wastewater: a review

Abstract. The removal efficiency of carbon (C) and nitrogen (N) in constructed wetlands (CWs) is very inconsistent and frequently does not reveal whether the removal processes are due to physical attenuation or whether the different species have been transformed to other reactive forms. Previous research on nutrient removal in CWs did not consider the dynamics of pollution swapping (the increase of one pollutant as a result of a measure introduced to reduce a different pollutant) driven by transformational processes within and around the system. This paper aims to address this knowledge gap by reviewing the biogeochemical dynamics and fate of C and N in CWs and their potential impact on the environment, and by presenting novel ways in which these knowledge gaps may be eliminated. Nutrient removal in CWs varies with the type of CW, vegetation, climate, season, geographical region, and management practices. Horizontal flow CWs tend to have good nitrate (NO3−) removal, as they provide good conditions for denitrification, but cannot remove ammonium (NH4+) due to limited ability to nitrify NH4+. Vertical flow CWs have good NH4+ removal, but their denitrification ability is low. Surface flow CWs decrease nitrous oxide (N2O) emissions but increase methane (CH4) emissions; subsurface flow CWs increase N2O and carbon dioxide (CO2) emissions, but decrease CH4 emissions. Mixed species of vegetation perform better than monocultures in increasing C and N removal and decreasing greenhouse gas (GHG) emissions, but empirical evidence is still scarce. Lower hydraulic loadings with higher hydraulic retention times enhance nutrient removal, but more empirical evidence is required to determine an optimum design. A conceptual model highlighting the current state of knowledge is presented and experimental work that should be undertaken to address knowledge gaps across CWs, vegetation and wastewater types, hydraulic loading rates and regimes, and retention times, is suggested. We recommend that further research on process-based C and N removal and on the balancing of end products into reactive and benign forms is critical to the assessment of the environmental performance of CWs.

Cost-Effectiveness Analysis of Surface Flow Constructed Wetlands (SFCW) for Nutrient Reduction in Drainage Discharge from Agricultural Fields in Denmark.

Constructed wetlands have been proposed as cost-effective and more targeted technologies in the reduction of nitrogen and phosphorous water pollution in drainage losses from agricultural fields in Denmark. Using two pig farms and one dairy farm situated in a pumped lowland catchment as case studies, this paper explores the feasibility of implementing surface flow constructed wetlands (SFCW) based on their cost effectiveness. Sensitivity analysis is conducted by varying the cost elements of the wetlands in order to establish the most cost-effective scenario and a comparison with the existing nutrients reduction measures carried out. The analyses show that the cost effectiveness of the SFCW is higher in the drainage catchments with higher nutrient loads. The range of the cost effectiveness ratio on nitrogen reduction differs distinctively with that of catch crop measure. The study concludes that SFCW could be a better optimal nutrients reduction measure in drainage catchments characterized with higher nutrient loads.

Mitigation of herbicide runoff as an ecosystem service from a constructed surface flow wetland

Ecosystem services provided by wetland systems presently play a pivotal role in intensive cropland as water purification from agricultural pollution. A field trial was conducted in 2014 to evaluate herbicide runoff reduction and retention using a 0.32 ha constructed surface flow wetland (CSFW) at the outlet of a 6 ha agricultural basin. To simulate an extreme pulse contamination, the CSFW was flooded with a runoff contaminated with metolachlor, and terbuthylazine and two other subsequent floods with pure water were applied 21 and 65 days later. Results show that the CSFW can reduce runoff concentration of metolachlor and terbuthylazine by a factor of 45–80 even in extreme flooding conditions. Herbicides retention in the CSFW was reversible, and the second and third floods mobilized 14–31 and 3.5–7.0% respectively, of the amount detected in the first flood. The CSFW performs a high buffer capacity for herbicides, capable to provide water purification service, protecting downstream surface water. Moreover, mitigation capacity of a CSFW for a heavy runoff from a 10 ha basin is 90% for every 50 m in length of a 15 m wide wetland. This confirms that the implementation of CSFWs in agro-systems can improve the sustainability of agricultural production.

Effects of annual harvesting on plants growth and nutrients removal in surface-flow constructed wetlands in northwestern China

Abstract The importance of harvest management for the growth and development of plants and nutrients removal in constructed wetlands (CWs) is highly controversial. This study evaluated the effects of annual harvesting on the growth and productivity of local Phragmites australis in northwestern China. Growth characteristics such as shoot density, biomass and height were studied using two pilot-scale surface-flow CWs over a two-year operation period. Plants were kept unharvested in one CW for comparative studies with the second CW, which was harvested at the end of the growing season. Each CW of 400 m2 was operated with a hydraulic loading of 34 m3/d for the treatment of water from an urban river polluted with municipal and industrial wastewater. The harvested CW recorded a higher shoot density (175 shoots/m2), biomass (1.4 kg/m2) and peak height (3.4 m) than the unharvested one (130 shoots/m2, 1.2 kg/m2 and 3.2 m). The overall nutrients removals were also slightly higher for the harvested CW (46.0% TN and 38.1% TP) than the unharvested CW (40.6% TN and 29.1% TP). Plants harvesting in the first year improved nutrients removal by plant uptake (41.9 g N/m2 and 3.7 g P/m2 versus 37.3 g N/m2 and 3.2 g P/m2) as well as in the substrate layer (216.9 g N/m2 and 8.0 g P/m2 versus 191.0 g N/m2 and 5.7 g P/m2) during the second year. Nonetheless, the increase in nutrients removal by harvesting was minimal.

Assessment of Suspended Solid Removal in a Surface Flow Constructed Wetland Using a Three-Dimensional Numerical Model

Surface flow constructed wetlands (SFCWs) have been widely used to treat various types of wastewater and stormwater due to the advantages such as low costs for operating and maintenance compared with conventional treatment systems. In SFCW, the flow pattern, which is determined by the geometric features including bed morphology and vegetation distribution, significantly influences the removal processes of suspended solids and other pollutants. In this study, a three-dimensional computational fluid dynamics model, that integrates hydrodynamic model and the Lagrangian particle tracking model, is applied to determine the effectiveness of a SFCW in removing suspended solids based on the predicted flow characteristics and distribution of suspended solids in the wetland. After the validation, the three-dimensional numerical model is applied to illustrate the three-dimensional internal flow pattern in the wetland. The predicted concentrations of suspended solids at several cross-sections in downstream direction are compared with the field sampling data and also the results from a traditional first-order decay model. The results show that the 3D model performs reasonably well predicting complex flow fields associated with complex wetland geometry. This study indicates that the 3D model is an effective tool to support the management and operation of field SFCWs. Also, it can help to improve the design of SFCWs providing better understanding of interactions among the geometric features, the flow characteristics and the contaminants behaviors.

Treatment of wastewater and restoration of aquatic systems through an eco-technology based constructed treatment wetlands – a successful experience in Central India

In the last couple of decades constructed wetlands (CWs) have drawn considerable interest in Central India. CWs offer an effective means of integrating wastewater treatment and resource enhancement, often at competitive cost in comparison to conventional wastewater treatments, with additional benefits of Green Urban Landscaping and wildlife habitat. This paper describes treatment performances and the design of some Sub Surface Flow CWs (SSFCW) and Artificial Floating Islands (AFIs) in Central India. Central Indian CWs show significant pollution reduction load for total suspended solids (TSS) (62-82%), biochemical oxygen demand (BOD) (40-75%), NH(4)-N (67-78%) and total Kjeldahl nitrogen (TKN) (59-78%). Field scale SSFCWs installed so far in Central India are rectangular, earthen, single/multiple celled having similar depths of 0.60-0.90 m, hydraulic retention capacity 18-221 m(3) with effective size 41.8-1,050 m(2). The major components of CWs incorporate puddled bottom/side walls, sealed with impermeable low-density polyethylene, a bed of locally available river gravel planted with Phragmites karka, and an inlet distribution and outlet collection system. A new variant on CWs are AFIs working under hydroponics. The field scale experimental AFIs installed in-situ in a slowly flowing local river were composed of hollow bamboo, a bed of coconut coir, floating arrangements and Phragmites karka as nutrient stripping plant species. The AFIs polish the aquatic system by reducing 46.6% of TSS, 45-55% of NH(4)-N, 33-45% of NO(3)-N, 45-50% of TKN and 40-50% of BOD. The study established that there is a need for further research and sufficient data to assist the development of CWs by instilling confidence in policymakers, planners and in the public.

An interval steady-state multimedia aquivalence (ISMA) model of the transport and fate of chloridion in a surface flow constructed wetland system treating oilfield wastewater in China

A surface flow constructed wetland (SFCW) system was built up to treat oilfield wastewater after secondary treatment. Chloridion (Cl−) in the wastewater was selected as an indicator to investigate the transport and fate of inorganic salts at high levels in the multimedia environments (air, water, soil, flora, and groundwater) by developing an interval steady-state multimedia aquivalence (ISMA) model. The modeled Cl− profiles were in good agreement with the measured ones, as indicated by the interval average logarithmic residual errors (IALREs) (<0.6 logarithmic units). The modeled results showed that the Cl− accumulated in the soil (70.80%) and was outputted from the environmental system mainly through periodic collection (34.86%) and advection outflow in groundwater (33.03%). It was also proved from imagery interpretation that the saline soil area was reduced 5.52% after wastewater irrigation, indicating that the tertiary treatment of oilfield wastewater through the constructed wetland was contributed to the local ecological restoration.

The ability of free water surface constructed wetland system to treat high strength domestic wastewater: A case study for the Mediterranean

This study evaluates a full-scale free water surface flow-constructed wetland (FWS-CW) system that was developed in 2005 to treat high strength wastewater in Garip village near Lake Eğirdir in the Mediterranean (Turkey). This FWS-CW was the one of the first full-scale wastewater treatment systems of this type in Turkey and the Mediterranean, and as such represents an important reference for the application of CW systems in other regions with similar climates. This FWS-CW system consists of two stages, the first one being comprised of a 3-compartment septic system with the second one comprised of the FWS CW. The treatment efficiency of the system was found to be significantly affected by the pollutant loading rates, hydraulic retention time and temperature. Long term monitoring revealed that the system removed approximately 86%, 92%, 56% and 43% of the total suspended solids (TSS), biochemical oxygen demand (BOD), total nitrogen (TN), and total phosphorus (TP) from the high strength domestic wastewater, respectively. Therefore, this type of FWS can be applied as economical, environment-sensitive and very efficient for TSS and BOD for treating high strength domestic wastewaters. Alternative measures for improving TN and TP are discussed.

Evaluation of a Surface Flow Constructed Wetland Treating Abattoir Wastewater

There is a growing need for decentralized wastewater treatment systems that support small abattoirs. Constructed wetlands (CW) are a potential solution; however, research on this subject has been limited to warm climates. Therefore, a research/demonstration site was established at a small-scale abattoir in Great Village, Nova Scotia, Canada. At the site, a 58.5-m2 two-celled surface flow CW with Typha latifolia was constructed. On average, the abattoir produced 0.75m3of wastewater per animal slaughtered (a mixture of cattle, pigs, and lambs) with an annual inflow of 124m3 and high monthly variability. The residence time of the CW (during the growing season) was determined by a tracer test to be 111d, and the active volume of the system was 89%. Overall, mass removals during two years of continuous monitoring were BOD5 (95%), TSS (72%), TDS (81%), TP (88%), SRP (97%), TKN (87%), and TAN (87%). The average E.coli level in wetland effluent (88 CFU 100 mL-1) was below the regulatory limit of 200 CFU 100 mL-1, although 13% of samples exceeded this value. Treatment efficiencies were generally higher during the growing season than the non-growing season.

Treatment of Polluted River Water Using Surface Flow Constructed Wetlands in Xinyi River Floodplain

Treatment of polluted river water with great variations of water quality using pilot-scale Surface Flow Constructed Wetland (SFW) was studied in this paper. The main results show that: When the influent concentrations of CODMn and NH4+-N were 11.69~60.00 mg•L-1 and 1.37~20.18 mg•L-1, the CODMn and NH4+-N removal rate of SFW which planted Lythrum salicaria, Canna indica, Typha latifolia and Scirpus locustris were 26.44％、40.12％、46.71％、28.23％ and 64.27％、70.49％、66.78%、58.52%. Typha latifolia and Canna indica have stronger ability for purifying pollutants. Scirpus locustris has strongest ability of overhead flooding, it can resist inundation over 22 days and still live. Lythrum salicaria has lowest ability of overhead flooding, it only can resist inundation 7 days.

Influence of design, physico-chemical and environmental parameters on pharmaceuticals and fragrances removal by constructed wetlands

The ability of several mesocosm-scale and full-scale constructed wetlands (CWs) to remove pharmaceuticals and personal care products (PPCPs) from urban wastewater was assessed. The results of three previous works were considered as a whole to find common patterns in PPCP removal. The experiment took place outdoors under winter and summer conditions. The mesocosm-scale CWs differed in some design parameters, namely the presence of plants, the vegetal species chosen (Typha angustifolia versus Phragmites australis), the flow configuration (surface flow versus subsurface flow), the primary treatment (sedimentation tank versus HUSB), the feeding regime (batch flow versus continuous saturation) and the presence of gravel bed. The full-scale CWs consisted of a combination of various subsystems (ponds, surface flow CWs and subsurface flow CWs). The studied PPCPs were ketoprofen, naproxen, ibuprofen, diclofenac, salicylic acid, carbamazepine, caffeine, methyl dihydrojasmonate, galaxolide and tonalide. The performance of the evaluated treatment systems was compound dependent and varied as a function of the CW-configuration. In addition, PPCP removal efficiencies were lower during winter. The presence of plants favoured naproxen, ibuprofen, diclofenac, salicylic acid, caffeine, methyl dihydrojasmonate, galaxolide and tonalide removal. Significant positive correlations were observed between the removal of most PPCPs and temperature or redox potential. Accordingly, microbiological pathways appear to be the most likely degradation route for the target PPCPs in the CWs studied.

Aquatic phytoremediation: Novel insights in tropical and subtropical regions

An overview of the state of the art in phytofiltration of nutrients and heavy metals (HMs) from wastewaters using tropical and subtropical plants in constructed wetlands (CWs) and lagoons is presented. Various mechanisms to remove these pollutants are discussed, in regard to three different types of systems: surface flow constructed wetlands (SFCWs), subsurface flow constructed wetlands (SSFCWs), and lagoons with floating plants. Only recent reports at laboratory, pilot and full scale, especially in tropical regions, are discussed. Most of the experiences around the world have shown that these systems are efficient and high removal percentages have been reported for both, nutrients and metals. However, there are still several unsolved or partially understood issues. Long-term studies at the mesocosms or large scale, in order to gain a full insight of the various mechanisms occurring in each system, are required. The understanding of the fate or compartmentalization of the pollutants in these complex artificial ecosystems, especially in the case of HMs, will permit us to establish the frequency of harvesting and the advantages of the use of specific species. The huge bio-diversity that is commonly found in tropical and subtropical regions represents a challenge for finding new species with outstanding characteristics for tolerance to toxic and recalcitrant pollutants or to extreme environmental conditions, such as high temperature or salinity.

Phosphorus reduction from agricultural runoff in a pilot-scale surface-flow constructed wetland

Excess P in surface waters in Quebec is the primary cause of water quality deterioration and the majority of it is coming from agricultural land as non-point source pollution. The objective of this study was to compare how two substrates, a sandy clay loam and a sand soil, influenced P retention in a surface-flow constructed wetland (CW). A secondary objective was to determine if the hydraulic residence time of the wetland differed between soil types. Measurements were taken at a pilot-scale CW site between July 5 and October 1, 2007. Three cylindrical tank replicates filled with sandy clay loam soil, and three with a sandy soil were planted with cattails ( Typha latifolia L.) and reed canary grass ( Phalaris arundinaceae L.). The tanks were flooded continuously with an artificial agricultural runoff solution containing 0.3 mg L −1 dissolved reactive P. The six treatment tanks retained 0.9–1.6 g P m −2, which corresponded to an average removal efficiency of 41%; there was no significant difference in the P retention by the two soil types. A bromide tracer test revealed a mean hydraulic retention time of 2.2 days for all tanks; however, the active volume of the sand tanks was greater. This investigation suggests that a sandy soil may be less prone to reducing conditions in a surface-flow CW and therefore maintain its role as a P sink for longer than the sandy clay loam.

Medium-term evolution of soil properties in a constructed surface flow wetland with fluctuating hydroperiod in North Eastern Italy

Knowledge of the evolution of soil properties in a constructed wetland is important for a correct design and performance assessment of the system over time.We evaluated the medium-term evolution of some chemical (pH, electrical conductivity [EC], organic carbon [OC], total nitrogen [TN], and total phosphorus [TP]) and physical (bulk density and penetration resistance) properties of the top soil layer in a constructed surface flow wetland (SFW) excavated in 1996 in North-Eastern Italy. The soil carbon sequestration performance of the SFW was assessed as well. Soil sampling was conducted in the years 1996, 2003, and 2007. During the period studied, the SFW was subjected to a fluctuating hydroperiod, receiving 56,000mm of water, 7 times higher than the rainfall. With respect to the initial homogeneous conditions, two layers differentiated in the top profile, characterized mostly by the different OC content and physical characteristics. OC and TN content increased only in the top layer (0–5 cm), from 7 to 17 g kg−1 and from 0.7 to 0.9 g kg−1 respectively, leading to an average C/N ratio of 19. The other chemical properties showed no significant changes over time.In 2003, the bulk density in the 0–5 cm layer (1.3cm3 g−1) was significantly lower than in 1996 (1.49 cm3 g−1), while at depths greater than 20cm this increased to more than 1.6 cm3 g−1, evidencing the formation of a compact layer. Penetration resistance increased along the profile as well. With reference to other land uses (buffer strips, manured cropland), SFWproved to be a valuable sink for CO2, accumulating 1.4 tCha−1 yr−1 which suggests a positive role in global warming attenuation.

Effects of wetland construction on water quality in a semi-arid catchment degraded by intensive agricultural use

Many factors can influence the improvement of water quality in surface-flow constructed wetlands (SFW). To test if water quality was improved, especially in nutrient and salt content, after passage through SFW, 11 wetland plots of various sizes (50, 200, 800 and 5000 m 2) were established within constructed wetlands on agricultural soils in the Ebro River basin (NE Spain) that had been affected by salinization. A set of 15 water quality parameters (e.g., nutrients, salts, sediments, and alkalinity) was obtained from samples collected at the inflow and outflow of the wetlands during the first 4 years after the wetlands were constructed. NO 3-N retention rates were as high as 99% in the largest (5000 m 2) wetlands. After 4 years, total phosphorus was still being released from the wetlands but not salts. Over the same period, in small wetlands (50, 200, and 800 m 2), retention rate relative to the input of NO 3-N increased from 40% to almost 60%. Retention of NO 3-N amounted to up to 500 g N m −2 per year, for an average load concentration at inflow of ∼20 mg l −1. Release of Na + declined from 16% to 0–2% by volume, for an average load concentration at inflow of ∼70 mg l −1. At the current retention rate of NO 3-N (76–227 g m −2 per year), 1.5–4% of the catchment should be converted into wetlands to optimize the elimination of NO 3-N.

Feasibility of using constructed wetland treatment for molasses wastewater treatment

The surface flow constructed wetland (SFCW) with Cyperus involucratus, Typha augustifolia and Thalia dealbata J. Fraser was applied to treat anaerobic treated-molasses wastewater (An-MWW) under the organic loading rates (OLRs) of 612, 696, 806, 929 and 1213 kg BOD 5 ha −1 day −1. The results showed that both removal efficiency and plant growth rate were increased with the decrease of organic loading rate (OLR). All tested-plant species could not grow under OLR of higher than 696 kg BOD 5 mg l −1 ( p > 0.05). Also, the plant-biomass of the systems was reduced by 10.4%, 26.5%, and 64.7% of initial plant-biomass under the OLR of 806, 929 and 1213 kg BOD 5 ha −1 day −1, respectively. However, all tested-plant species showed the same pattern on the plant-biomass production yield and removal efficiency. The highest SS, BOD, COD, total phosphorus, NH 4 + , NO 3 - and molasses pigments (MP) removal efficiencies of 90–93%, 88–89%, 67%, 70–76%, 77–82%, 94–95% and 72–77%, respectively were detected under the OLR of 612 kg BOD 5 ha −1 day.

Organic micropollutant removal in a full-scale surface flow constructed wetland fed with secondary effluent

The mass emission rate of 12 pollutants from a wastewater treatment plant (WWTP) secondary effluent into a small tributary of the River Besòs (northeastern Spain) was determined. The pollutants tested included pharmaceutical and personal care products (PPCPs) and herbicides. Furthermore, a 1-ha surface flow constructed wetland (SFCW) was evaluated for pollution removal. Whereas the low concentration values (ng L −1) of PPCP discharge into the tributary was comparable to inter- and intra-campaigns, herbicides and a veterinary drug (flunixin) exhibited a high variability in concentrations (μg L −1). Moreover, removal efficiencies were often higher than 90% for all compounds, with the exception of carbamazepine and clofibric acid (ca. 30–47%). As expected, a seasonal trend of pollutant removal in the wetland was observed for compounds with low biodegradation and moderate photodegradation rates (i.e. naproxen and diclofenac).