Assessment of treatment efficiency of constructed wetlands in East Ukraine
Résumé
The aim of the study was to evaluate the performance of 9 hybrid constructed wetlands (CWs) in the Kharkiv region, East Ukraine. Assessed CWs varied by surface areas (from 760 to 11,000 m(2)) and treated domestic wastewater discharge (10 m(3) day(-1) to 700 m3 day(-1)). Principal macrophyte species used on these CWs were the Reed Phragmites australis (Cav.) Steud., the Wood Bulrush Scirpus sylvaticus L. and the Broad-leaved Cattail Typha latifolia L. The studied CWs demonstrated high removal efficiency on BOD5 (82.6 +/- 11%), COD (77.3 +/- 9%) and suspended solids (72.1 +/- 9%). The removal rates of nitrogen, orthophosphates and surfactants ranged from 9% to 52%. The overall removal efficiency of CWs was dependent mainly on inflow pollutant concentrations, design, maintenance parameters and operating conditions. Comparing to conventional domestic wastewater treatment facilities the CWs showed similar efficiency on the majority of controlled parameters. At the same time the estimated construction and operational costs of CWs were significantly lower compared to the conventional wastewater treatment facilities of similar capacities that makes CWs application feasible for small communities in rural areas. In order to improve the removal capacity of studied wetlands, operational conditions should be adjusted to the inflow concentrations and received wastewater volumes.