VFCW Tom1

Ecotechnology Design and Optimization

Subsurface-flow (SSF) treatment wetlands (constructed wetlands) are a decentralized wastewater ecotechnology commonly used for the treatment of domestic wastewater prior to soil dispersal or surface water discharge. Compared to conventional wastewater treatment technologies, treatment wetlands offer many advantages: low operation costs, simple to operate, and can be constructed out of locally-available materials. These factors led to the widespread use and implementation of treatment wetlands in areas for which centralized sewage treatment is not a cost-effective option.

Aerobic conditions are a prerequisite for effective removal of BOD, COD, and ammonia-nitrogen in subsurface-flow wetlands. While it is accepted that oxygen transfer via plant roots does occur, the extent to which it provides oxygen in excess of plant respiration is uncertain. There are few studies that have aimed to directly measure plant-mediated oxygen transfer rates, however, the general conclusion is that these rates are insignificant relative to the oxygen demand exerted by wastewater under common loading conditions. As a result, many current wetland designs neglect plant-mediated oxygen transfer altogether.

The limited oxygen-transfer capability of conventional horizontal subsurface flow wetland designs has led to the development of alternative design configurations that improve subsurface oxygen availability. These enhanced designs aim to provide sufficient oxygen for BOD removal and nitrification through means of shallow bed depth, intermittent dosing regime with unsaturated flow, frequent water level fluctuation, or direct mechanical aeration of the gravel substratum. Although these alternative design configurations are gaining increased attention in the literature and in practice, design standards do not exist in even the most recent literature.

Research studies at the UFZ aim to bridge the gap between scientific results and application in real-world design by comparing multiple design alternatives side-by-side under the same wastewater and climatic conditions. The results of these investigations will be used to comparatively explore the relative merits of different ecotechnology design configurations and to further develop and optimize wetland design approaches such as the first-order, tanks-in-series P-k-C* model that is useful to scientists and engineers alike.


Contact

Dr. Jaime Nivala

Tel.: 0341 235 1851
Fax: 0341 235 1830

jaime.nivala@ufz.de