Comparison of interannual removal variation of various constructed wetland types

Department of Biodiversity and Environmental Management, Faculty of Biologic and Environmental Sciences, University of León, Campus de Vegazana s/n, E-24071 León, Spain.
Science of The Total Environment (Impact Factor: 4.1). 05/2012; 430:174-83. DOI: 10.1016/j.scitotenv.2012.04.072
Source: PubMed

ABSTRACT Seven mesocosm-scale (1m(2)) constructed wetlands (CWs) of different configurations were operated outdoors for thirty-nine months under the same conditions to assess their ability to remove organic matter and nutrients from urban wastewaters. CWs differed in some design parameters, namely the presence of plants, the species chosen (i.e., Typha angustifolia or Phragmites australis), the flow configuration (i.e., surface flow or subsurface flow) and the presence/absence of a gravel bed. It was observed that, in general, removal efficiencies decreased with the aging of the system and that seasonality had a great influence on CWs. A comparison was made in order to figure out which kind of CW was more efficient for the removal of every pollutant in the long term. Planted systems were clearly better than unplanted systems even in winter. Efficiency differences among CWs were not extremely great, especially after a few years. However, some types of CWs were more adequate for the removal of certain pollutants. The effect of the aging on the main parameters involved in pollutant removal in CWs (temperature, pH, conductivity, dissolved oxygen concentration and redox potential) was assessed. The efficiency of CWs should not be evaluated based on short monitoring periods (1-2 years) after the start-up of the systems, but on longer periods.

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    • "Wetlands can be used as a secondary or tertiary treatment step, following chemical and/or biological treatments, and rely upon natural processes in shallow water or temporarily flooded land that is able to support aquatic life [18]. These systems tend to be less resource-intensive than conventional wastewater treatment plants [5,18], and have been used successfully for treatment of municipal sewage in small communities, as well as for some industrial wastewaters [19]. While most research has focused on the use of wetlands for reduction of nutrients and biochemical oxygen demand (BOD) in water bodies receiving runoff from agricultural or urban sources [6,20], recent studies have shown that these systems might remove PPCPs as well [1,6,18,21]. "
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    ABSTRACT: Background The discharge of complex mixtures of nutrients, organic micropollutants, and antibiotic resistance genes from treated municipal wastewater into freshwater systems are global concerns for human health and aquatic organisms. Antibiotic resistance genes (ARGs) are genes that have the ability to impart resistance to antibiotics and reduce the efficacy of antibiotics in the systems in which they are found. In the rural community of Grand Marais, Manitoba, Canada, wastewater is treated passively in a sewage lagoon prior to passage through a treatment wetland and subsequent release into surface waters. Using this facility as a model system for the Canadian Prairies, the two aims of this study were to assess: (a) the presence of nutrients, micropollutants (i.e., pesticides, pharmaceuticals), and ARGs in lagoon outputs, and (b) their potential removal by the treatment wetland prior to release to surface waters in 2012. Results As expected, concentrations of nitrogen and phosphorus species were greatest in the lagoon and declined with movement through the wetland treatment system. Pharmaceutical and agricultural chemicals were detected at concentrations in the ng/L range. Concentrations of these compounds spiked downstream of the lagoon following discharge and attenuation was observed as the effluent migrated through the wetland system. Hazard quotients calculated for micropollutants of interest indicated minimal toxicological risk to aquatic biota, and results suggest that the wetland attenuated atrazine and carbamazepine significantly. There was no significant targeted removal of ARGs in the wetland and our data suggest that the bacterial population in this system may have genes imparting antibiotic resistance. Conclusions The results of this study indicate that while the treatment wetland may effectively attenuate excess nutrients and remove some micropollutants and bacteria, it does not specifically target ARGs for removal. Additional studies would be beneficial to determine whether upgrades to extend retention time or alter plant community structure within the wetland would optimize removal of micropollutants and ARGs to fully characterize the utility of these systems on the Canadian Prairies.
    Chemistry Central Journal 03/2013; 7(1):54. DOI:10.1186/1752-153X-7-54 · 2.19 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the effect of different horizontal constructed wetland (CW) design parameters on solids distribution, loss of hydraulic conductivity over time and hydraulic behaviour, in order to assess clogging processes in wetlands. For this purpose, an experimental plant with eight CWs was built at mesocosm scale. Each CW presented a different design characteristic, and the most common CW configurations were all represented: free water surface flow (FWS) with different effluent pipe locations, FWS with floating macrophytes and subsurface flow (SSF), and the presence of plants and specific species (Typha angustifolia and Phragmites australis) was also considered. The loss of the hydraulic conductivity of gravel was greatly influenced by the presence of plants and organic load (representing a loss of 20% and c.a. 10% in planted wetlands and an overloaded system, respectively). Cattail seems to have a greater effect on the development of clogging since its below-ground biomass weighed twice as much as that of common reed. Hydraulic behaviour was greatly influenced by the presence of a gravel matrix and the outlet pipe position. In strict SSF CW, the water was forced to cross the gravel and tended to flow diagonally from the top inlet to the bottom outlet (where the inlet and outlet pipes were located). However, when FWS was considered, water preferentially flowed above the gravel, thus losing half the effective volume of the system. Only the presence of plants seemed to help the water flow partially within the gravel matrix.
    Water Research 12/2012; 47(3). DOI:10.1016/j.watres.2012.12.010 · 5.53 Impact Factor
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    ABSTRACT: Between 1978 and 2008, 13 avian botulism outbreaks were recorded in the wetlands of Mancha Húmeda (Central Spain). These caused the deaths of around 20,000 birds from over 50 species, including globally endangered white-headed ducks (Oxyura leucoceophala). Here, a significant association was found between the number of dead birds recorded in each botulism outbreak and the mean temperature in July (always >26°C). The presence of C. botulinum type C/D in wetland sediments was detected by real-time PCR (qPCR) in 5.8% of 207 samples collected between 2005 and 2008. Low concentrations of Cl(-) and high organic matter content in sediments were significantly associated with the presence of C. botulinum. Seventy five digestive tracts of birds found dead during botulism outbreaks were analysed; C. botulinum was present in 38.7% of them. The prevalence of C. botulinum was 18.2% (n = 22 pools) in aquatic invertebrates (Chironomidae and Corixidae) and 33.3% (n = 18 pools) in necrophagous invertebrates (Sarcophagidae and Calliphoridae), including two pools of adult necrophagous flies collected around bird carcasses. The presence of the bacteria in the adult fly form opens up new perspectives in the epidemiology of avian botulism since these flies may be transporting C. botulinum from one carcass to another.
    Applied and Environmental Microbiology 05/2013; 79(14). DOI:10.1128/AEM.01191-13 · 3.67 Impact Factor
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