CWA AquaEnviro Conference (18-19 September 2012)

1. CWA AquaEnviro Conference(18-19 September 2012) An investigation in the hydraulic and treatment performance of vegetated SuDS AlexandrosTsavdaris (PhD student) e-mail:alexandros.tsavdaris@port.ac.uk GeorgiosRoinas (PhD student) e-mail:georgios.roinas@port.ac.uk School of Civil Engineering and Surveying Project Supervisors: Dr. John Williams john.williams@port.ac.uk Dr. Steve Mitchell steve.mitchell@port.ac.uk Dr. Catherine Mantcatherine.mant@port.ac.uk

2. Wetlands at Portsmouth • Gravel Bed Hydroponics 1980’s-1990’s • UK; Egypt • Colombia; Greece • Phytoremediation with reeds • Oil Pollution • MoD • Road Runoff • A34 Newbury Bypass – 1995-2000 • Newlands MDA 2005-2010

4. Current Work in Vegetated Systems • 2 Projects • Hydraulics and Sedimentation in vegetated SuDs • Fate of hydrocarbons (TPH, PAHs) in SuDs – particularly source control vs non-source control. • Local case study intensively studied and additional sites used for comparison. • Local Roads • Trunk Roads • Housing Development

5. CASE STUDY 1: LOCAL ROAD • Newlands MDA, Waterlooville, Hampshire • Major Development, 2000+ new dwellings on greenfields – Grainger PLC • SuDs designed by Mayer Brown Ltd • KTP UoP intended to study SuDs in construction – but focused on an access road pond due to project delays

6. Access Road Swale and Vegetated Pond

7. Vegetated Basin Swale

8. Site Description • Permanent water depth of 1m (rising to 1.60 m) • Storage capacity 306 m3 • Receives road-runoff from an adjacent to road swale. • Treated water ↔ River Wallington ↔ The use of tracers is prohibited. Sediment Traps (ST) ↔ monitoring purposes Auto-Samplers at inlet/outlet ↔ storm analysis

9. Monitoring • Water Quality in Basins and River • Normal conditions • Storm Flow • BOD, COD, TSS, VSS, Amm-N, Conductivity, metals, TPH, PAHs • Sediment and soils • Sediment Catch Traps – quantity, metals, PSD • Soils – TPH, PAHs • Flows and Vegetation

10. Water Quality in the System • Low values of Ammonium and Ec compared to the River. • Decrease from B1 to B2 suggests good treatment performance regarding the specific water quality indicators. [n=11]

11. Settling Solids-Sediments B2 B1 Inlet Outlet B1 B2 TSS, mg/l VSS, mg/l • [n=15]Within the basins 50%-60% of settling solids are volatile, much higher than sediment at the Inlet/Outlet, indicating decaying vegetation or other organics within the system. B2 seems to have more volatile substances than B1. • [n=15] Significantly more settling solids were found in B1 compared to B2 with similar proportion of coarse (>63um) and fine (<63um) particles. [n=15]

12. Particle Size Distribution • Inlet sediment ↔ Coarser particles than Outlet sediment. Coarse particles ↔ Easily constrained by vegetated systems. Finer particles ↔ Difficult to control (Zanders, 2004) • Settling solids range from 5 to 80 µm with no significant differences between d(0.5) across the system. Settling Solids B2 B1

13. Water Quality- Storm Events

14. STORM EVENT: TPH Waterlooville Site

16. Heavy Metals in Water • Heavy metals are found both in the particulate and soluble fractions • Indication that the River is more polluted than the pond system. • Concentrations of HM in water vary with season with the lowest values during the summer.

17. Platinum Group Elements Water Settling Solids • PGE are associated with catalytic converters and auto-mobile activity. • Pd and Rh have strong correlation both in settling solids and water samples • Generally, Pd conc. much higher than Rh conc., as observed by Whiteley and Murray (2003), no significant difference between particulate and soluble fractions.

18. Impacts of Construction • Since construction began there has been a significant increase in the SCOD and Ca in runoff. • Impact of construction on SuDS requires further research.

19. CASE STUDY 2 – TRUNK ROADS • Two Sites • A34 Newbury Bypass • M27 Itchen Branch • Both vegetated ponds • Allows higher loadings to be compared and different pond shapes • A34 Source Control –M27 Concrete Road + no-source control

20. A34 Newbury Bypass – Ponds B and C • Various configurations and planting • Source Control: Porous asphalt, oil interceptors and sediment traps

21. A34 Newbury Bypass – Ponds B and C

22. M27 Itchen Branch • Motorway runoff • No-source control • Rectangular layout

23. M27 Itchen Branch

24. TPH in Trunk Road Runoff by Season

25. CASE STUDY 3 – RESIDENTIAL DEVELOPMENT • Cambourne, Cambridgeshire Steve Wilson (EPG ltd) - EU Demonstrative site (map from CIRIA)

26. Cambourne • Swales and basins in series serving a housing development • Also allows a comparison with a neighbouring catchment with no SuDs

27. S2

29. CFD Model Development • Newlands pond used for the development of a CFD model with ANSYS 12.1 Fluent Software • Field monitoring and lab studies used to model of flow through reeds, will be combined with sedimentation and PSD data • Allow CFD models of different pond morphologies and planting to be investigated to investigate sedimentation and pollutant removal. • Most vegetated SF wetland models have incorporated porous zones to account for impact of aquatic vegetation. • Emergent vegetation poses different problem as the stems act in a different manner.

30. LABORATORY STUDY • Flow around individual stems investigated in a hydraulics flume (L=4m, b=0.3m) • Site survey data showed two different vegetation densities in the shallow, and deep zones within the pond • The Flume was run with no vegetation and with simulations of the shallow and deep vegetation densities under two different inflows. • Velocity fields measured with a Valeport 810 electromagnetic current meter. • CFD model of flume with no vegetation, individual stems and porous zones compared.

31. Flume Vegetated region No Veg. • Good agreement between experimental and CFD results for no vegetation and individual stem configurations • Porous zone model under-predicted the velocity field in the vegetated zone (also observed by Li and Zeng, 2009), but did predict the increase/decrease of velocity seen before and after the vegetation. VD-Deep-Porous Vegetated region VD-Deep-IS

32. Pond-CFD Flow scenario 1: Max Inflow (35 l/s) Max water level (1.5 m) • So far porous zone model of pond produced. Stem model not appropriate large scale. • The non vegetated pond has generally lower velocities in the basins • Vegetation enables preferential flow paths and circular motion within the pond as well as velocity increase in the shallow zones. Also observed by Saggiori, S. (2010) • However, vegetation reduces the velocity downstream of B1 as also observed in the flume experiment. Vegetation – Porous Zone No Vegetation

33. Conclusions • Road runoff is a highly variable influent. • Site specific and seasonal variation; first flush during storm events highly significant. • Wetland systems have shown good removals of pollutants. But dynamic nature means that this is not always progressive. • Initial CFD model has been created for flow in SF wetlands and ponds. • Will be refined and improved to assess pollutant removal in different pond shapes and planting.