Source control pollution in sustainable drainage: final report

Background Source control in sustainable drainage systems (SUDS) terminology refers to the application of the technology close to where incident rainfall lands. It can provide the opportunity for the degradation of individually minor, widely dispersed pollutants close to the source of pollution. However, the degree to which source control of pollution through SUDS carries a risk to groundwater is unclear. There is insufficient evidence available to allow safe policy development, despite statutory business drivers stemming from the Groundwater Directive and Water Environment Water Services (Scotland) Act. It is generally accepted by researchers and practitioners that the 'treatment train approach' for SUDS technology can be regarded as best practice. But hard environmental data is needed if regulators are to justify this approach and require it through some form of regulation or legislation. Currently, it is unknown which type sustainable drainage systems are most effective for the important classes of urban diffuse pollutants (such as oil, PAHs, FIOs and nutrients). Similarly, evidence is needed on whether PAHs and oil actually degrade in a swale system, filter drain network or detention basin en route to a regional pond, and, if so, how this compares to an end-of-pipe pond solution for a conventionally drained system. Additional questions arise about how nutrients can be best managed in urban catchments and whether it would be beneficial for regulators to require grass/soil source control treatment in sensitive catchments. The proposed project The project intends to demonstrate the efficacy of various SUDS techniques in the degradation of a range of diffuse source pollutants, and how these compare to more traditional drainage techniques. The project aims to establish the evidence base to aid future policy development in this area. The target audience will be scientists and engineers, policy makers, regulator staff, water utilities and road authorities. The project will be in two phases. Phase 1 will provide background information, identify suitable sites, as well as develop and test methodologies . Phase 2 will focus on field monitoring and artificial dosing experiments. The research objectives of this project are to: Determine the risk of movement of pollutants through soil into groundwater in soft-engineering SUDS; Measure the degradation of oil and PAHs, and fate of phosphates and nutrients in soft engineering SUDS; Identify the degradation products in a range of SUDS techniques; Determine the conditions for the optimal breakdown of oil and PAHs in the range of SUDS investigated; Determine the conditions for the optimal nutrient uptake or stabilisation within a range of SUDS techniques; Provide monitoring data for existing SUDS facilities, and conduct experimental work to aid the interpretation of the field site data.