Konstantinos N. Moutsopoulos

Comparative Modeling of HSF Constructed Wetland Performance With and Without Evapotranspiration and Rainfall

The effects of meteorological parameters, i.e., evapotranspiration (ET) and rainfall (P), on the flow and BOD fate in horizontal subsurface flow constructed wetlands (HSF CW) are presented based on numerical simulation, using the Visual MODFLOW-MT3DMS code, which is based on the finite difference method. This model was used to simulate five HSF CW pilot-scale units, which were constructed and operated in the Laboratory of Ecological Engineering and Technology. Experimental data from these facilities were used to calibrate and verify the numerical procedure. ET was estimated based on a previous study proposing the use of the Blaney-Criddle method, and was introduced in the model. For a characteristic time period, rainfall values from observed events were also entered in the model. The model was then used to test effects of ET and rainfall on effluent concentration under various conditions, showing a more intense effect of ET and a less significant effect of rainfall. It was also used in test runs comparing the performance, without and with ET, under various vegetation, porous media size, HRT and temperature conditions.

Numerical simulation of phosphorus removal in horizontal subsurface flow constructed wetlands

AbstractThe removal of total phosphorus (TP) in horizontal subsurface flow constructed wetlands (HSF CW) is numerically investigated using the Freundlich linear isotherm for adsorption. For the numerical simulation, the Visual MODFLOW code family, based on the finite difference method, was used. This model is applied in the simulation of five pilot-scale HSF CWs. Influent–effluent TP concentration experimental data from these facilities were used to first calibrate this model and derive appropriate values of the distribution coefficient Kd and the first-order removal coefficient λ. Then, the model was verified using the values of λ and Kd from calibration and independent experimental data from these facilities. The calibrated model was applied to comparatively simulate differences in removal efficiency under various design and operational parameters.

A computational approach for remediation procedures in horizontal subsurface flow constructed wetlands

A large-scale computational approach for groundwater flow and contaminant transport and removal in porous media is presented. Emphasis is given to remediation procedures in horizontal subsurface flow constructed wetlands. For the numerical procedure, the MODFLOW computer code family is used. Application is made for the simulation of horizontal subsurface flow wetlands pilot-scale units, constructed and operated in Democritus University of Thrace, Xanthi, Greece. The effects of the inlet and outlet recharge positions to the optimum contaminant removal are also numerically investigated.

Modelling Alternative Feeding Techniques in HSF Constructed Wetlands

The effects of two alternative operational techniques, i.e., effluent recirculation and step-feeding, on the removal of Biochemical Oxygen Demand (BOD) in Horizontal Subsurface Flow Constructed Wetlands (HSF CWs) are evaluated numerically. These include two feeding techniques: under the first technique, a percentage of the effluent is re-introduced to the wetland inlet; while under the second, wastewater is introduced to the HSF CW at several points along the flow path. For the numerical simulation, the Visual MODFLOW family code was used. This model has been calibrated using experimental data collected in five HSF CW pilot-scale units. Application of the model to study effluent recirculation showed that this operation mode does not improve the performance of the Constructed Wetlands (CWs), which seems to decrease as the effluent recirculating quantity increases. Although recirculation dilutes the influent pollutant concentration, the decrease in Hydraulic Residence Time (HRT), due to the additional flow entering the system, seems to act negatively on CW performance. For the step-feeding case, various values of the step-feeding percentage factors have been investigated at three inflow points along the CW. Again, the results showed no performance improvement. Thus, both operation modes are not recommended for HSF CWs.

Water supply of Greek cities: the WFD and the principles of integrated water resources management

ABSTRACT In this paper, the water supply conditions in the major Greek cities have been investigated and a comprehensive description is provided. It has occurred that the choice of the catchment area as the administrative unit for water management purposes is rather more adapted to urban water management in Western Europe, than in Greece. In fact, while the major cities in France, Spain and the UK can be mainly supplied by water issued from the catchment area in which they are located, interbasin water transfer is necessary in Greece. The reasons are both hydrological, with the typical catchment area size in Greece being rather small, and because the economic activities of the Greek cities are not linked to rivers; so only a few of them are built on large watersheds. The reduction of water losses due to network leakage is suggested as a method for the decrease of interbasin transfer volumes.