Efficiency of constructed reed bed and reed pond as tertiary wastewater treatment stages during their start-up period

A sand bed and a pond; both vegetated by reed (Phragmites australis), were monitored since their construction in summer 1997 till winter 1999/2000.The mean capacity during the study period equaled 79 ± 21 m3d−1. The flow behind the secondary clarifier was divided equally between the reed bed and the reed pond, both of the same surface area about 300 m2, giving the same hydraulic loads of 132 ± 35 mm d−1. The pH, TC, TOC, IC, N-NO3−, N-NH4+, NTotal, P-PO43− and PTotal have been analysed at the inlet and outlet of both systems The performance of the secondary stage was sufficient except for nitrification (11.2–45.4 mg N-NH4+ dm−3 in the effluent from the secondary clarifier). No significant improvement in ammonia removal in the constructed wetlands has been observed. However, the nitrates quantities has been reduced by half. The investigations revealed better removal of suspended solids, total nitrogen and phosphorus by the reed bed than by the pond. The differences were greater during cold seasons.