Horizontal sub-surface flow constructed wetlands Ondřejov and Spálené Poříčí in the Czech Republic – 15 years of operation

Horizontal sub-surface flow constructed wetlands (HF CWs) Ondřejov and Spálené Poříčí have been in operation since 1991 and 1992, respectively, and are the oldest systems in the Czech Republic. CW Ondřejov treats sewage from 362 PE in a single 806m2 bed planted with Phragmites australis. CW Spálené Poříčí treated wastewater from 700 PE from a combined sewerage until 2001 and then another part for additional 700 PE was completed in 2002. At present, there are six beds planted with a mixture of P. australis and Phalaris arundinacea with a total area of 5000m2. Constructed wetland Ondřejov treatment performance has been very steady over the period of operation and exhibited ‘‘typical’’ efficiency for organics (average BOD5 inflow and outflow concentrations of 198 mg l−1 and 18 mg l−1, respectively) and suspended solids (average inflow and outflow concentrations 204 mg l−1 and 9mg l−1, respectively). Removal of phosphorus is steady but low with average inflow and outflow concentrations of 10.9 mg l−1 and 6.5 mg l−1, respectively. Average ammonia-N removal amounted to only 19.4% with an average outflow concentration of 22.8 mg l−1. Constructed wetland at Spálené Poříčí treated diluted wastewater until 2002. After that about 700 people were connected directly to the sewerage without local pretreatment. The average inflow and outflow BOD5 concentrations for the whole period were 44.2 and 5.7 mg l−1, respectively. Average TSS removal amounted to 89.1% with an average outflow concentration of 7.9 mg l−1. Both systems are examples of well-operated constructed wetlands.