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Constructed wetlands (CW) are a treatment option for agricultural wastewater. Their ability to adequately function in cold climates continues to be evaluated as they are biologically active systems that depend on microbial and plant activity. In order to assess their performance and to highlight regional specific design considerations, a review of CWs in Eastern Canada and the Northeastern USA was conducted. Here, we synthesize performance data from 21 studies, in which 25 full-scale wetlands were assessed. Where possible, data were separated seasonally to evaluate the climatic effects on treatment performance. The wastewater parameters considered were five-day biochemical oxygen demand (BOD5), total suspended solids (TSS), E. coli, fecal coliforms, total Kjeldahl nitrogen (TKN), ammonia/ammonium (NH3/NH4+-N), nitrate-nitrogen (NO3--N), and total phosphorus (TP). Average concentration reductions were: BOD5 81%, TSS 83%, TKN 75%, NH4+-N 76%, NO3--N 42%, and TP 64%. Average log reductions for E. coli and fecal coliforms were 1.63 and 1.93, respectively. Average first order areal rate constants (ka, m•y-1) were: BOD5 6.0 m•y-1, TSS 7.7 m•y-1, E. coli 7.0 m•y-1, fecal coliforms 9.7 m•y-1, TKN 3.1 m•y-1, NH4+-N 3.3 m•y-1, NO3--N 2.5 m•y-1, and TP 2.9 m•y-1. In general, CWs effectively treated a variety of agricultural wastewaters, regardless of season. [ABSTRACT FROM AUTHOR]

Certain ions such as Na+ and Cl- can accumulate in recirculating greenhouse nutrient solutions and can reach levels that are damaging to crops. An option for the treatment of this problem is phytodesalinization with Na+ and Cl- hyperaccumulating plants that could be added to existing water treatment technologies such as constructed wetlands (CWs). Two microcosm experiments were conducted to evaluate eight plant species including Atriplexprostrata L. (triangle orache), Distichlis spicata (L.) Greene (salt grass), Juncus torreyi Coville. (Torrey's rush), Phragmites australis (Cav.) Trin. ex Steud. (common reed), Spartina alterniflora Loisel. (smooth cordgrass), Schoenoplectus tabernae-montani (C.C. Gmel.) Palla (softstem bulrush), Typha angustifolia L. (narrow leaf cattail), and Typha latifolia L. (broad leaf cattail) for their Na+ and Cl- accumulation potential. An initial (indoor) experiment determined that J. torreyi, S. tabernaemontani, T. angustifolia, and T. latifolia were the best candidates for phytodesalinization because they had the highest Na+ and Cl- tissue contents after exposure to Na+ and Cl--rich nutrient solutions. A second (outdoor) experiment quantified the Na+ and Cl+ ion uptake (grams of each ion accumulated per m² of microcosm). J. torreyi, S. tabernaemontani, T. angustifolia, and T. latifolia accumulated 5.8,3.9, 8.3, and 9.2 g ⋅m-2 of Na+ and 25.7,18.2,31.6, and 27.2 g ⋅m-2 of Cl-, respectively. Of the eight species, T. latifolia and S. tabernaemontani showed the greatest potential to accumulate Na+ and Cl- in a CW environment, whereas A. alterniflora, D. spicata, and P. australis showed the least potential. [ABSTRACT FROM AUTHOR]