Thirty years of constructed wetlands for municipal wastewater treatment in the Czech Republic

Constructed wetlands (CWs) for wastewater treatment have been used in the Czech Republic since 1991. Nowadays, there are about 200 full-scale constructed wetlands for treatment of municipal sewage. Most CWS have been designed with horizontal subsurface flow, in the late 2010s and early 2020s, combination of vertical and horizontal flow or two-stage vertical flow CWs have been used. The average number of designed PE is 235 and the average surface area of the Czech CWs is 1132 m2. The average treatment efficiencies are 87.5% for BOD5, 78.5% for COD, 85.7% for TSS, 41.8% for N-NH4 and 41% for TP. The respective average outflow concentrations are (in mg l- 1): 12.5, 48.5, 11.2, 16.6 and 3.35. The results from the oldest CWS in the Czech Republic revealed very consistent performance over the period of 30+ years with no refurbishment. The paper also provides information about two CWs which were refurbished after about twenty years of operation from horizontal subsurface flow to hybrid systems. In both CWs, the refurbishment was successful and the treatment efficiency increased.