Constructed wetlands for the removal of water treatment additives from saline industrial wastewater.
Constructed wetlands (CWs) are man-made wetland systems, isolated from the natural environment, that employ the natural treatment capacity of natural systems for the removal of contaminants from water streams. Throughout the world, CWs have been employed as an alternative for or in addition to different forms of domestic- and industrial wastewater treatment. CWs are often considered to be a suitable (secondary) wastewater treatment option because of their low maintenance effort and costs, low energy requirements and their integration in the landscape. Various contaminant removal processes occur in simultaneously in CWs: anaerobic and aerobic biodegradation, photodegradation, plant uptake and adsorption to the soil matrix.
The dominating removal process in a CW depends on its design. For instance, photodegradation occurs mainly in surface flow constructed wetlands, while aerobic and anaerobic biodegradation can be found in batch fed vertical subsurface flow CW. In addition, the removal efficiency of CWs are influenced by the choice of substrate, vegetation, hydraulic retention time and the climatological circumstances.
The removal efficiency of CWs for various emerging contaminants is well studied. However, no information on the removal of water treatment additives from saline industrial waste water streams in constructed wetlands is available. In my PhD-project, I will study the feasability of a constructed wetland for the removal of this compounds from saline industrial waste water streams and develop the most optimal CW design to do this. To perform this study, I chose various representative water treatment chemicals for different industries :
- Benzotriazole, corrosion inhibitor
- DBNPA, biocide
- Glutaraldehyde, biocide
- PEG, surfactant
- HEDP, antiscalant
- NMTP, antiscalant
With this chemicals, I will perform different batch scale studies to elucidate their fate in CWs :
- Biodegradation experiments, in which the influence of the salinity and shockdosing of biocides and the formation of transformation products will be studied
- Photodegradation experiments, in which the susceptibility of the chemicals for photodegradation, the formation of transformation products, and the influence of water depth and DOM will be studied
- Adsorption experiments, in which the adsorption efficiencies of different substrates, competition with DOM and break-through times will be studied
In addition, I will design pilot scale CWs in which the removal efficiency for a (synthetic) wastewater spiked with the chemicals of interest will be tested. Because it is hypothesized that a combination of different CW designs will likely result in the highest removal efficiency, these pilot scale CWs will consist out of different sequences of CW designs in order to find the most optimal CW sequence (Fig 1).
