Constructed Wetlands for landfill leachate

Removal efficiencies

Constructed wetlands for landfill leachate treatment show good removal efficiencies, which can vary according to different sizes, hydraulic regimes, and primary treatments (Wojciechowska et a., 2010).

Average removal efficiencies from different Polish and Sweden case studies. (Wojciechowska et a., 2010)

A good design guarantees high removal efficiencies. For instance, mean removal efficiencies registered from 7 Slovenian case studies were: BOD5 68%, COD 73%, N-NH3+ 75%, TP 73%. The CW WWTP treating the leachate from the landfill of Chunchulala in Mobile County (Alabama – USA) has shown the following average performances: TSS 97%, COD 90%, TOC 87%. The landfill of Laflèche, Eastern Ontario, treats the landfill with a CW WWTP which was monitored the first two years of operations, showing high mean removal of organic load (95%) and ammonia (99%). Satisfactory organic removal were observed also in cold climates; for instance, the CW treating the leachate from the landfill of the Municipality of Kodiak Island, in Alaska, had mean removal of 40% for COD and 36% for ammonia, high metal removal (99% for Fe and 44% for Mn), and a clear effluent. Good performances were observed also in long term monitoring, as shown by Bulc (2006), which monitored a landfill leachate treatment plant for 7 years, reporting constant removal efficiencies of 50% for COD, 59% for BOD5 and 51% for ammonia.

Influent and effluent COD concentration correlated with precipitation for 7 years of monitoring of a CW for landfill leachate. Bulc (2006)

Constructed wetlands coupled with Sequencing Batch Reactors (SBRs).

The combination of SBR and CW is one of the most promising options of integration between nature-based and technological solution for wastewater treatment (Liu et al., 2015). SBR+CW scheme was often adopted in the UK for leachate treatment. Indeed, about 80 treatment plant for with SBR+CW scheme is reported (Mulamoottil et al., 1999). One example is the landfill of Judkins Quarry (UK), reported in the following picture.

Areal view of the SBR+CW plant for treatment of leachate from the Judkins Quarry landfill (UK).

Bulc, T. (2006). Long term performance of a constructed wetland for landfill leachate treatment, Eco. Eng. 26, 365–374.

Kadlec, R. H. & Wallace, S. D. (2009). Treatment Wetlands, 2nd edition. CRC Press, FL, ISBN: 978-1-56670-526-4.

Liu, R, Zhao Y., Doherty L., Hu Y. & Hao, X. (2015).A review of incorporation of constructed wetland with other treatment processes, Chem. Eng. J. 279, 220–230.

Mulamoottil, G., McBean E.A. & Rovers, F. (1999). Constructed wetlands for the Treatment of Landfill Leachates. CRC Press, FL, ISBN: 1-56670-342-5.

Wojciechowska, E, Gaiewska M., & Obarska-Pempkowiak, H. (201o).Treatment of Landfill Leachate by Constructed Wetlands: Three Case Studies, Polish.J. Environ. Stud. 19(3), 643–650.