Long term treatment performance of constructed wetlands for wastewater treatment in mountain areas: Four case studies from the Czech Republic

• All constructed wetlands perform high removal efficiency under mountain conditions.
• Treatment performance for organics and suspended solids is excellent.
• Removal of organics and ammonia is steady throughout the year.

Four constructed wetlands with horizontal subsurface flow situated 500 m a.s.l. were surveyed in order to evaluate long-term treatment efficiency. The results revealed that treatment performance of all surveyed constructed wetlands is excellent for organics and suspended solids and varied between 88% and 94% for BOD5, 67% and 85% for COD and 74% and 96% for TSS. Removal of NH4+-N in CWs Zásada has improved over the time of operation and average treatment efficiency amounted to 53%. There was no difference between summer and winter NH4-N outflow concentrations. Average removal of TP amounted to 59% and the removal efficiency was very stable over the 18 years of operation.

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