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Title: Enhancing the potential of constructed wetlands for treatment of micro-point source effluents
Author: Green, Verity
ISNI:       0000 0004 6494 1694
Awarding Body: Lancaster University
Current Institution: Lancaster University
Date of Award: 2015
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Chemical pollution of freshwaters is a globally-significant concern. Micro-point sources of wastewater, including caravan sites and other recreational locations, contribute increasingly to freshwater pollution, particularly as other point and diffuse sources are addressed more effectively. Constructed wetlands (CWs) represent one approach to treatment of wastewater from micro-point sources. This thesis considers how treatment within CWs could be enhanced to meet the challenges inherent to micro-point sources of wastewater. Whilst CWs can deal effectively with a range of pollutants, uncertainties surround the removal of nitrogen (N), phosphorus (P) and, under certain circumstances, biochemical oxygen demand (BOD) within these systems. These uncertainties, coupled with variable but often high pollutant loadings from micro-point sources, represent key research challenges. This thesis examines whether amendment of CWs with reactive industrial by-products, coupled with recirculation of wastewater, offers the potential to address these challenges. The sorption properties of a range of industrial by-products, including alum sludge from water treatment works, ochre from minewater treatment and biochar produced from various feedstocks, were assessed through batch and microcosm studies. Ochre and alum- based water treatment residuals demonstrated significant potential to remove phosphate from solution, whilst softwood biochar exhibited substantial ammonium sorption capacity. Mesocosm studies examined the potential to use combined by-products in conjunction with wastewater recirculation to enhance pollutant removal. However, combined reactive media and recirculation were not found to improve treatment levels significantly compared to traditional CW systems. Finally, a field trial was undertaken to assess the extent to which a CW was able to treat a micro-point source of wastewater, alongside the effectiveness of recirculation. Recirculation at the field-scale improved, or maintained, the level of treatment for a range of pollutants. The modifications to CW design and operation evaluated in this thesis offer the potential to enhance the treatment of wastewater from micro-point sources whilst maintaining the low cost and sustainable basis to the CW approach.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available