This study focussed on the treatment of stormwater runoff using constructed wetlands (CWs): man-made systems engineered to replicate the treatment processes in natural wetlands. The main aims were to design and assess a novel configuration of CWs for stormwater treatment, while contributing to the further understanding of pollutant removal in CWs through the development of models to explain internal processes and predict performance. A vertical tidal-flow CW operational regime was applied to target enhanced nitrogen removal while maintaining high removal rates a range of high priority urban stormwater pollutants. Eight pilot-scale CW models were built to investigate the effect of key design and operational variables: substrate media, wetland surface area, and wetting and drying regimes. The performance of the systems was considered successful when compared to results of similar pilot-scale CWs that operated without tidal flow. Results show that all eight models effectively reduced concentrations of solids and metals, with load reductions generally in excess of 90%. Nutrient removal – particularly nitrogen - was heavily affected by design and operation variables. Significantly, nitrogen removal in the systems outperformed similar pilot-scale CWs with alternative hydraulic operating conditions. Understanding of the internal CW treatment processes were backed up through statistical analysis and numerical modelling. These techniques highlighted important mechanisms such as the biological transformation of nitrogen and the importance of TSS removal to heavy metals reduction. Overall, results show that the CW design has great potential for reduction of solids, metals and nutrients in stormwater. Further research at a field scale would better represent the performance of the systems in practice, and closer monitoring of dissolved oxygen and redox potential would enhance understanding of internal processes, particularly regarding nutrient behaviour. Results of this study can contribute to future CW research and design, through increased understanding of long-term pollutant removal in these types of system. In time, this may result in the wider application of CWs for stormwater treatment to make human water use more sustainable and better protect the environment.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:685499 |
| Date | January 2015 |
| Creators | Lucas, Rhodri |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/91254/ |
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