Monitoring and flux determination of trace metals in rivers of the Seversky Donets basin (Ukraine) using DGT passive samplers

International audienceThis paper reports the results of the in situ application of diffusive gradients in thin-films (DGT) passive samplers for trace metals (Cd, Co, Cr, Cu, Ni, Pb and Zn) monitoring in transboundary Udy and Lopan rivers of the Seversky Donets watershed in the Kharkiv region (Ukraine), which has a long history of industrial development. The research discusses potential sources of DGT-measured labile metals in water and seasonal variations. Our results demonstrate the application of DGT for identifying and measuring labile metal concentrations in contrasted climate conditions (cold snowy winter and hot summer) and appropriateness of such a tool for continuous water monitoring with the presence of an ice cover. Results show that DGT-measured concentrations of most of trace metals were much higher downstream of the wastewater treatment plants discharges than upstream; thus wastewater treatment plants seemed not able to reduce or to remove trace metals' contaminations and become major sources of pollutants in the studied rivers. The calculation of the average metal fluxes based on the DGT-measured concentrations confirmed that the urban wastewater discharges significantly contribute to the metal fluxes into the Udy and the Lopan rivers during both low-flow and high-flow periods. Compared to the wastewaters inputs to the rivers, the transboundary effect is limited, but should be taken into account as the origin of some metals is from sources located on the adjacent Russian territory

Assessment of treatment efficiency of constructed wetlands in East Ukraine

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

Assessment of treatment efficiency of constructed wetlands in East Ukraine

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

Formation and properties of sediments in constructed wetlands for treatment of domestic wastewater

Sediments formation and biogeochemical properties were studied in an experimental constructed wetland site in Ukraine (Bioplato) for treatment of domestic effluents. The wetland, with a capacity of 50m(3) d(-1) of wastewater, consists of vertical and horizontal filtrations units with fine gravel, middle and coarse sand, a subsurface flow unit with natural wetland soil applied, and a septic tank and sludge-drying field. Macrophytes, reed (Phragmites australis), cattail (Typha latifolia) and a number of sedge species (Carex spp.) were planted in the area and dominate the average cover of 85-90%. Treatment efficiency for BOD5 and suspended solids was 93-96%, for COD - 82%, for nutrients - 27-50%, and for pathogenic microorganisms 99.3-99.6%. Sludge was sampled at each unit followed by standard laboratory analyses of its main characteristics: total organic carbon (TOC), total nutrients (N, P), contents of trace elements, abundance of pathogenic microorganisms, and general toxicity. Results confirmed that the top layer of sludge from each unit of wetland could be used as a source of fertilizers for grain and leguminous crops