The implementation of the Water Framework Directive (WFD) will impose new phosphorus (P) consents (<1 mg/L) for small sewage treatment works (STW) in the UK. This poses a challenge for water utilities, as while the conventional solution of chemical dosing and tertiary filtration would be able to meet those consents, it does not align with the low energy technology requirements of small STW. Constructed wetlands with
Basic Oxygen Furnace (BOF) steel slag and apatite not only are passive systems with low maintenance requirements and low energy demand, but they can also effectively meet those new consents, therefore, providing a more sustainable alternative to the conventional solution. This technology has traditionally been tested in small-scale short-term column trials, which limits its full-scale extrapolation potential.
This thesis provides field-scale and long-term direct comparison of both media for P removal, and determines key operational parameters for optimum performance, such as hydraulic retention time and media size, as well as identifying operational challenges. The suitability of the commonly employed column experiments to test reactive media is also assessed and recommendations are provided for extrapolation to other STW. Performance comparison to other two trials with BOF steel slag in the UK allows to determine the potential for full-scale application of this technology in the country. Circumstances under which this technology can be economically viable compared to the conventional solution are then assessed.PhD in Wate
