A laboratory study to assess the hydraulic and water treatment performance of geotextiles within simulated filter drains Anne-Marie McLaughlin, Dr. Stephen Coupe, Dr. Luis Sañudo-Fontaneda, Daniel Castro-Fresno and Elena Blanco-Fernandez

Structure 1.Introduction 1.1. Definition and Characteristics 1.2. Aims and applications 1.3. Applications in SuDs 1.4. Research history 1.5. Current research at CU 2.Project aim 3.Methodology 3.1. Materials 3.2. Methods 4.Results 4.1. Hydraulic behaviour 4.2. Sediment attenuation 4.Future Work 2

1.1. Definition and Characteristics The term ‘geotextile’ was introduced by Jean-Pierre Giroud in Geosynthetic: “Generic term describing a product, at least one of whose components is made from a synthetic or natural polymer, in the form of a sheet, a strip or a three dimensional structure, used in contact with soil and/or other materials in geotechnical and civil engineering” ISO (2006) 3

Geosynthetic barrier GeogridGeotextile Geocomposite 1.2. Aims and Applications Geotextiles are an emerging environmental technology that has been successfully researched. 4

1.3. Application in SuDs Porous structure and permanence is an essential property in SuDs. Research on the use of geotextiles in PPS has been extensive and has proven to be advantageous. Geotextiles are made of plastic polymer fibres or threads Fig. (Lee and Borudeau 2006) 5

1.3. Application in SuDs Diagram of a highway filter drain In a filter drain geotextiles are used as a wrapping layer 6

1.3. Application in SuDs Micro-organisms (including bacteria, fungi and protists) form a mature self-regulating biofilm. Fig. (a) SEM biofilm (b) TEM bacteria from effluent (c) Cilliate of genus Colpoda (d) Testate amoeba genus Euglypha (e) Rotifer (Coupe, 2004) 7

1.4. Research history 8

1.5. Current research at CU Research on novel highway filter drains 9

Structure 1.Introduction 1.1. Definition and Characteristics 1.2. Aims and applications 1.3. Applications in SuDs 1.4. Research history 1.5. Current research at CU 2.Project aim 3.Methodology 3.1. Materials 3.2. Methods 4.Results 4.1. Hydraulic behaviour 4.2. Sediment attenuation 4.Future Work 10

Project aim Overall project aim: To test the hydraulic and water quality performance of new geotextile designs in simulated filter drains 11

Project aim Preliminary study aim: To identify two suitable geotextiles from the range of new designs in terms of hydraulic behaviour and water quality performance. 12

Structure 1.Introduction 1.1. Definition and Characteristics 1.2. Aims and applications 1.3. Applications in SuDs 1.4. Research history 1.5. Current research at CU 2.Project aim 3.Methodology 3.1. Materials 3.2. Methods 4.Results 4.1. Hydraulic behaviour 4.2. Sediment attenuation 4.Future Work 13

3.1. Materials Rig numberDescription 1.1Oleophobic material 1.2Oleophobic material (reversed side up) 2.1Hydrophilic material 2.2Hydrophilic material (reversed side up) 3Hydrophobic material 4Needle punch material 5Thin needle punched material Table 1. Description of the candidate materials and the control rigs. 14

3.2. Methods Laboratory recreation of a storm event to test the ability of the geotextiles to retain sediments Separate additions of sediment in 10g, 50g and 100g were made to the surface of the buckets Washed through with 2000ml (200ml/min) of tap water and the effluent collected in bottles A 500ml subsample was filtered to determine the mass of sediment deposited 15

3.2. Methods The second stage of the testing programme: Hydraulic performance: Prior to contamination, 4 rainfall intensities of 50, 100, 200 and 400mm/hr at increasing durations of 5, 10 and 15minutes in filter drain structures. Water quality and clogging: pollutants will be added together with a rainfall intensity of 400mm/hr for 15mins duration. 16

3.2. Methods The second stage of the testing programme for water quality: Oil retention by Horiba and heavy metal concentrations by ICP-OES. CO2-O2 balance will be measured to assess the treatment of organic pollution. Microbiological variables will be determined by plate counts and phase contrast microscopy. 17

Structure 1.Introduction 1.1. Definition and Characteristics 1.2. Aims and applications 1.3. Applications in SuDs 1.4. Research history 1.5. Current research at CU 2.Project aim 3.Methodology 3.1. Materials 3.2. Methods 4.Results 4.1. Hydraulic behaviour 4.2. Sediment attenuation 5. Further work 18

4.1. Hydraulic behaviour Fig. Cumulative discharge volume registered for all the candidate materials used in the experiments and the control rig with no geotextile during the 10 minutes storm event simulated in the laboratory. 19

Fig. Discharge rates registered for all the candidate materials used in the experiments and the control rig with no geotextile during the 10 minutes storm event simulated in the laboratory Hydraulic behaviour 20

4.2. Sediment attenuation None of the buckets released more than 1g/l of sediment following any single sediment application. Final cumulative sediment mass discharged was significantly less than 1% of the total sediment applied to the surface. Fig. Visual water quality of water collected after passing through the buckets. 21

Fig. The mass of sediment discharged from buckets containing the geotextiles with 3 masses of added sediment to the surface Sediment attenuation 22

Structure 1.Introduction 1.1. Definition and Characteristics 1.2. Aims and applications 1.3. Applications in SuDs 1.4. Research history 1.5. Current research at CU 2.Project aim 3.Methodology 3.1. Materials 3.2. Methods 4.Results 4.1. Hydraulic behaviour 4.2. Sediment attenuation 5. Further work 23

5. Further work Geotextile 3 (thick hydrophobic) performed the best in terms of sediment removal Geotextile 1.2 (hydrophilic reverse side up) presented the best hydraulic performance in terms of the attenuation levels and infiltration rates. These two geotextile materials have been chosen for the second stage of this project. 24

5. Further work Geotextile 1Geotextile 2TerramControl Geotextile 1.2Geotextile 3A control and industry standard (Terram) No geotextile 3 rigs 1 rig Table 1. Treatment rig numbers and components 25

Anne-Marie McLaughlin Coventry University 26