WCW26

The introduction of dosed vertical flow biofilters, DVFBs, a form of submerged constructed wetland for municipal wastewater treatment, have proven successful in cold climate regions of northern Europe, principally in Austria, Germany, Denmark and Poland.   This technology should not be confused with the very successful French system for use in temperate climates.  The primary differences between cold climates and temperate climates are the survival of plants during the winter in temperate climates and the dormancy of plants during the winter in cold climates; and, the fact that surface water will freeze.  Only submerged constructed wetlands are used in cold climates to avoid complexities associated with freezing.  The Canadian environment is a cold climate.  Initial attempts in using DVFB technology in Canada for treatment of municipal wastewater, while still in the development stage, are promising.
 
Computer modelling (simulation) of the combined hydraulics and treatment processes inherent to the DVFB technology have had limited success.   The flow through the filter bed of a DVFB is a complex mixture of saturated and unsaturated flow that can be successfully modelled despite its complexity.  But, while the treatment processes are generally known, their kinetics have not been accurately identified and models which attempt to combine the simulation of hydraulics with the treatment processes have not been able to reliably reproduce observations of flow or quality of treatment.  Consequently, most design activity relies on the growing body of information from those installations which are performing satisfactorily.
 
The combined hydraulic and treatment kinetics (CHTK) model described uses a combination of the accurate identification of the treatment processes and associated kinetics, an understanding of the hydraulics of the dosing process together with the experience and knowledge gained from successful DVFB facilities in Europe that are enshrined in the form of national guidelines and standards.  Procedures to implement the CHTK model have been developed.
 
The potential for successfully using DVFB technology throughout Canada, a cold climate, is greatly increased with the use of the CHTK model.