10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005
Pervious pavement research in Spain: Hydrocarbon degrading microorganisms J.R. Bayon1*, D. Castro1, X. Moreno-Ventas1, S.J. Coupe2 and A.P. Newman2 1
Escuela T. S. de Ingenieros de Caminos, C. y P., Universidad de Cantabria, Avda. los Castros, Santander, 39005, Spain 2 School of Science and the Environment, Coventry University, Priory Street, Coventry, CV15FB, UK * Corresponding author, e-mail
[email protected]
ABSTRACT Pervious pavements have made an important contribution to stormwater quality improvements in sustainable urban drainage systems, particularly as part of a treatment train approach. In Spain however this approach has hardly been addressed. This paper outlines the emerging research in a collaboration between UK and Spanish Universities aimed at establishing a research infrastructure to allow the study of pervious pavements to be carried out taking into account local conditions in the northwest of Spain. Parallel with the development of locally-appropriate porous pavement structures a biological study dealing with the hydrocarbon degrading efficiency is taking place. Experiments are reported utilising different locally available surfaces and sub-base materials in which microorganisms are introduced from a variety of contaminated sites to act as an inoculum. In addition to effluent analysis aimed at measuring the degree of hydrocarbon retention/degradation, experiments will be reported on the physical characteristic of the different materials used. This research addresses the influence, not only of the different surface and sub-base materials but also of the different types of geosynthetics used. It is intended that this research will establish criteria for the further development of a design for hydrocarbon-degrading pervious pavement structures in Spain.
KEYWORDS Degradation; geotextile; microorganisms; Pervious pavement
INTRODUCTION The use of pervious pavements in flow control within urban drainage systems and also as a treatment to improve water quality, has been tested in a number of countries (Pratt et al., 1996; Pratt et al., 1999; Dierkes et al., 2002; Newman et al., 2002). In Spain this application is currently insignificant, not only with the use pervious pavements but also with SUDS (Sustainable Urban Drainage Systems) and BMPs (Best Management Practices) generally. The encouragement of a sustainable approach to drainage is a major driver for further study of these systems. Therefore to this purpose, collaboration has been initiated between Cantabria and Coventry Universities. This originated as a successful grant application in 2003, with the project itself initiated in 2004. This collaboration represents the first serious attempt to research pervious surfaces in Spanish conditions from microbiological perspective. Not only
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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005 will climate and locally available materials be different but also construction practices and the legal framework surrounding the implementation of these technologies. The aims of this project are: - Experimentation of pervious surfaces under Spanish conditions in laboratory and field applications. - Evaluation of which materials are better for these purposes in Spain. - Development of a design manual of pervious pavements in Spain. - To further consider products suited for use in specialist areas such as water harvesting applications. The presentation will report the up-to date results of the ongoing and currently developing experiments, but this paper mainly aims to describe the progress made in establishing the research infrastructure from a zero base (with respect to microbiology of pervious surfaces) within the University of Cantabria. It is hoped that this will act as a stimulus to encourage other groups in Spain to enter into this important field of research.
METHODOLOGIES It was necessary to carry out experiments under laboratory conditions, where environmental conditions may be controlled and indicators of microbial activity could be monitored. It was also essential to perform experiments under more realistic field conditions; this was considered important, as the knowledge base built up in the lab scale experiments would be important to inform further field research. On-going experiments Oil extraction efficiency. Gravimetric method. This first study analyses the efficiency of oil extraction, improving the familiarity of the researchers with the techniques and the extraction power of the oil extractor rig, in this case, a Selecta Det-Gras oil extraction rig (Solvent recovery extractor for the determination of fast and oil “Det-gras”). The investigation was carried out with relatively high oil loadings since it was envisaged that at some stage the indoor models would be tested by loading the models to an extent that free product could breach the oil retaining capacity of the geotextile. This investigation was carried out in the Environmental Engineering of Laboratories at Cantabria University (Torrelavega, Spain) and consisted of a direct extraction of clean oil (Ertoil Supermultigrado 20W-50 DG). The technique involves extraction of the free product oil from the flasks by sorption with cotton pieces (hydrophilic cotton), extraction of these pieces into n-hexane and evaporation of the solvent prior to a gravimetric determination using a balance with 0.1 mg precision. The oil reference samples were prepared in 100 ml volumetric flasks in three different proportions 1%, 2% and 10%. Study on water harvesting applications. In addition to the experiments on standard PPS (Pervious Pavements Structures) systems, a need has been identified to consider techniques of minimising evaporation when a PPS is used for the storage of water and subsequent water harvesting. To this end a new geocomposite product Inbitex-Composite™ (Formpave Ltd, Coleford, UK) has been subjected to initial tests Inbitex-Composite™ is a combination of a geotextile and an impervious vapour barrier bonded around a water-conducting core. Two experiments have been carried out, one is a test of the evaporation control properties of this material and the other is an investigation into the ability of the geotextile layer used in this combination to maintain its oil retaining and oil biodegrading capabilities. This material is
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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005 intended to replace a high proportion of the geotextile in a pervious pavement used for water harvesting, particularly for irrigation purposes. This experiment has been carried out in model pavement systems in plastic drums with a surface area of 0.055m2. These initial experiments have been carried out in Coventry with the intention that they will be repeated in the heat of the Spanish summer later in the year. The colonisation test was carried out in a laboratory model arranged so as to provide a mixture of locally pooled water and dry geotextile layers, as would be experienced in reality, and the Inbitex-Composite™ has been harvested for electron microscope investigations after 8 weeks. Experiments Planned and Under Construction Laboratory study of pervious pavements. This experiment was developed to investigate the hydrocarbon retention and biodegradation effectiveness of pervious pavements with a selection of locally available, materials under a variety of rainfall events. The system will be studied by comparing the effluent quality and the microbiological activity (Coupe et al., 2003). Representative models of pavement section, (Pratt et al, 1996,1999), have been housed in black HDPE bins having a plan area on the top of the bin of 1,695 cm2 and a height of 550 mm. Sixteen models were used distributed in four different groups. Eight of the sixteen models were designed with concrete blocks and the other eight with porous asphalt. Two kinds of sub-bases were used, both recycled concrete (Puehmeier et al., 2004) and limestone aggregate, in both cases with the minimum size being restricted to 15 mm. Four models, one in each group of similar structure, were used as standard ones and were treated with an inhibitor of biological growth to compare the effectiveness of biological and physical processes in the purification of water. The entire structure was completed with a polypropylene funnel located at the base of the bin and a HDPE reservoir for effluent collection. All models have small holes (forty of 2 mm) at the bottom to allow the flow of the effluent, (Figure 1).
CAPTION Electrovalve Gas measure device
Programable relay Plastic bin Gas pipe
Figure 1. Laboratory Test Rig Layout
The biological activity was monitored by a measurement system that control CO2, VOC (volatile organic compounds), temperature, moisture and O2, continuously inside the plastic bins. All the measures were recorded in a PC and devices are used to do it: IAQRAE (CO2, VOC, Temperature, Moisture) and QRAE PLUS (O2) are both products of RAE Systems. The sampling system was controlled by a series of electro-valves operated via a controller (Programmable Relay Zelio Logic), itself under control of the PC. The monitoring infrastructure of these models has taken a considerable time to establish and those entering Bayon et al.
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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005 this field of study should take this aspect into consideration when project planning. The effluent is analysed on total hydrocarbons with a Horiba OCMA 310 instrument, based on solvent extraction and infra-red spectrometry. It was considered that this system needed a comparative technique to be compared with and thus one of the early experiments reported in this paper is the initial study on the suitability of the Selecta Det-Gras system for this purpose. Other parameters analysed are BOD5, COD and pH. At the time of writing this laboratory test had just started. The results will be available at the conference but the first steps have been taken, such as the design of representative structures of pavement, and an adequate monitoring system have provided an important insight into the problems associated with establishing these experiments. In addition to indoor models, fullscale trials outdoor trials involving 16 outdoor versions of the lab models are also under construction. Field tests of pervious pavements. The field site was a car park close to La Guía Sportive Centre in Gijón. It is believed that this is the first full-scale trial of a PPS in Spain. The existing site has an area of 22,000 m2 with 798 car-parking bays, all of which have plastic cells grassed system. Each bay was designed 5 m long, 2.50 m wide and with a horizontal slope. The experimental area under construction consists of fifteen monitored bays, designed for low traffic. Three different surfaces are considered: concrete blocks, porous asphalt and plastic cells with grass (Atlantis). Six bays are surfaced with concrete blocks, six more with porous asphalt and the last three bays with grassed plastic cells as standard on the rest of the site. The concrete block-surfaced bays consist of 200 mm x 100 mm (plan) x 100 mm depth (Montserrat concrete blocks), a 50 mm bed of clean pea gravel and geotextile (Terratest TMA 125 or similar). Two types of sub-base are used: recycled concrete in three bays and clean limestone aggregate in other three, both without small sizes. The last layer consists of a plastic cell (Atlantis or similar) without fill and undersealed to allow the drainage to the reservoir tanks. The porous asphalt surface bays consist of two layers, 50 mm thick each, of porous asphalt (PA-12), a geotextile (Amopave or similar), 250-350 mm variable sub-base with recycled concrete in three bays and clean limestone aggregate in other three, both with a minimum size of 15 mm, and finally the Atlantis plastic cells are directly undersealed. In addition there are three bays with plastic cells which are monitored at the surface to compare the effectiveness of the rest of car bays in the site. These bays are porous only in the first 50 mm (plastic cells) and the sub-base is of blast furnace slag with a low infiltration rate and without drainage system inside. All details can see in Figure 2. The Gijón test site is currently under construction with the experimentation starting in February, hence we will be able to show the first results for 10 ICUD to provide a useful comparison with laboratory data.
5.00 m
6.00 m
Variable
Concrete kerb
Plastic cell grassed "Atlantis"
Reservoir tank
Impermeable Asphalt
Concrete kerb 2%
2% 0%
Blast furnace slag
Classic drainage system Plastic cell undersealed
Geotextile Porous asphalt 2% or concrete blocks Variable sub-base: Drainage system Recycled concrete or limestone
Figure 2. Cross section of test structures. 4
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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005 Biofilm development and growth in geotextile. Although it is often reported in the UK that hydrocarbon retention and biofilm development on geotextile surfaces is best when using a thermally bonded random mat geotextile no work appears to have been done on nonpolyolefin based geotextiles (particularly polyester which has great recycling potential) and there has been no effort to investigate the relative suitability of materials available locally in Spain. To this end this experiment studies the growth of biofilm in the various geotextiles normal used in Spanish roads, under known liquid medium conditions, to determinate which geotextile has a better behaviour to support a microbial community. This experiment is somewhat more controlled than those previously carried out in the UK (Newman et al., 2002) and although it does not well reflect the reality of a PPS model it provides the relative ability of the geotextiles to support biofilm to be considered under conditions that random variations from model to model are eliminated. This experiment initially looks at the general biofilm forming properties with further work required to confirm that these are reflected when hydrocarbons are he sole energy source. A plastic tank (Figure 3) is used with internal dimensions 892 mm x 302 mm (plan) x 178 mm depth, which can contain different lines of geotextile hanging down (Nafiz, 2003). The liquid medium used for cultivation is introduced in the tank with known characteristics, yeast extract 2 g/L, meat peptone 2.0 g/L, solution of phosphate tampon (APHA 1985), Ph 7.2, and providing air to maintain an aerobic atmosphere with air pumps, which supplied through a plastic pipe bubbler along the full length of the tank bottom. The tank is covered to prevent light penetration. The liquid medium is conveyed between both extremes of the tank to maintain the same characteristics of the liquid medium and to avoid a additional variation.
P e ris ta ltic Pum p I n f lo w
S t r ip
G e o t e x t ile
A ir b u b b le s
0 .0 3 9 m
0 .1 7 8 m
0 .0 6 5 m
W e ig h t
A ir b u b b le s
S t r ip
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G e o t e x t ile
A ir b u b b le r A ir Pum p
P e r is t a lt ic Pum p 0 .3 0 2 m
P e r is t a lt ic Pum p O u t f lo w A ir Pum p
O u t f lo w P e r is t a lt ic Pum p
I n f lo w
W e ig h t 0 .8 9 2 m
Figure 3. Biofilm growth and develop testing device.
Ten different geotextiles are used with 65 mm x 39 mm size and their properties are listed on Table 1. The geotextiles are hung in six different lines and each two lines have fifteen pieces of geotextile containing ten types with three replicas. At different ages of the experiment, strips are taken off to measure and analyse the biofilm thickness, weight and microscopic characteristics. This latter characteristic being found to be the most useful. To date only preliminary results of biofilm development and growth in geotextiles are available. Early indications are that the non-woven polypropylene geotextiles will be the most suitable but following further literature studies it has been decided to extend this test to a range of further suppliers materials. (Danosa, Terratest, Polyfelt, Fibertext, Naue). The properties of the selected products are shown in table 1. More significantly this apparatus has been shown to be working very reliably and the results of this experiment will be available at the conference. Bayon et al.
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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005 Table 1. The properties of geotextiles used. Product Name Characteristic 2 Mass (g/m ) Material Thickness (mm) Geodren Pes ARX 120 120 PP/T 0.61 Polyfelt TS 30 155 PP 1.50 Danofelt PP 125 125 PP(70%) Danofelt PY 150 150 PY 1.90 Danofelt PY 200 200 PY 2.10 Terratest TMA-125 125 PP/T(1face) 1.10 Pavemat B 140 PP 1.40 Secutex 151 GRK 3 150 PP 1.8 Fibertex G 100 100 PP 0.6 Fibertex F2B 140 PP 0.8 (PP): Polypropylene / (PY): Polyester / (T): Thermally bonded.
Opening Size O90 (µm) 160 110 150 100 90 90 110 130 110 110
RESULTS AND DISCUSSION Oil extraction efficiency. Gravimetric method The results of oil extraction efficiency experiments with the Det-Gras device can be seen in Figure 4. Results for the sample with a concentration of 1%, show that the efficiency is approximately the same through the all experiment, although the second sample (replication) has a low result. On the contrary, samples with concentrations of 5% and 10% show irregular efficiencies due to errors introduced by laboratory operator, that is why the number of operations are more than those in samples with less concentration. Hence the later samples of high concentrations have better efficiency than initially. Total efficiencies were 97.82 %, 96.89 % and 93.91 % respectively.
Concentration 1% Concentration 5% Concentration 10%
Efficiency(%)
100,00% 80,00% 60,00% 40,00% 20,00% 0,00% 0
1
2
3
4
5
6
7
Sample
Figure 4. Results of oil extraction efficiency experiments.
Water Harvesting Applications Figure 5A shows that in UK conditions, within five weeks the amount of water evaporating from the Inbitex-Composite™ models is significantly less than from the Terram 1000® models. In practice this would be used in a pervious surface with geotextile-covered water infiltration slits provided. Other work has shown this to be even more significant if the edges 6
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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005 of the textiles are sealed around the edge of the container and thus evaporation is highly dependent on the ratio of sealed to unsealed edges and infiltration slits. Much further work is needed in optimising this aspect of the application and, in particular, realistic trials under hot dry conditions such as a Spanish summer will be needed. It is very promising that the upper geotextile layer has been shown (figure 5B) to be capable of sustaining an oil degrading biofilm despite the fact that the underlying drainage produces very different conditions from those normally obtained in a geotextile in a pervious pavement.
(B) Figure 5- A: Mean mass of water remaining in unsealed barrels covered with Terram 1000®, Inbitex-Composite™ geosynthetics and no geotextile. B: Biofilm Formed on InbitexCompositeTM.
CONCLUSIONS The present paper describes several long-term and ongoing experiments intended to analyse the possibility of measurement and control of porous pavements, emphasizing the quality of effluent through the biological activity. It also presents the first sets of results from a number of other experiments aimed at validating the analytical methods used and at investigating the properties of a geocomposite when used in water harvesting investigations. It is clear that the oil extraction by gravimetric method is not an easy technique to obtain a good efficiency when the precision is very strict, due to the large number of factors that affects the method. Thus, the conclusions are as follows: •
Firstly, how the percentage efficiency can be improved significantly when laboratory operators have more analytical experience. • Secondly, high oil concentrations are not easy to extract with the Selecta DetGras. This is due to the low efficiency of washing off small amounts of residual oil from glassware. The solution in this case may be to reduce the volume of samples. Despite this and taking into consideration the percentage of error that we are introducing with the procedure, it can be a good system of comparison in order to check other devices. In the water harvesting experiment it can be seen that there is great potential for the use of this new geocomposite:
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10th International Conference on Urban Drainage, Copenhagen/Denmark, 21-26 August 2005 • •
The material is suitable for the formation of oil degrading biofilm and in a simulated PPS application, oil retention occurs at a rate sufficient at least for biofilm formation. The evaporation potential is demonstrated although further work is required for it to shown be suitable for use in Spanish summer conditions.
Future work in this area will need to involve an assessment of risk from the development of pathogens during the long-term the stored water under relatively warm conditions. Laboratory and field tests are now starting and all monitoring systems are optimised to measure the behaviour and efficiency of biological processes hydrocarbon-degradation. This is the beginning of a three-year research programme and it is hoped that results will accrue more quickly after initial testing. Collaboration between UK and Spanish Universities in this area is a timely development for the promotion of sustainable drainage in Spain.
ACKNOWLEDGEMENTS The authors wish to thanks Spanish Ministry of Science and Technology and FEDER (European Funds for Regional Development).We also want to thank the collaboration of Coventry University, Bloques Montserrat SL, DL Ingeniería, Horiba Spain, Rae Systems Spain, Fibertex Geotextiles, TMA Terratest Medio Ambiente, Naue Fasertechnik and Drenajes y Geotextiles Danosa. Special thank to Environment Engineer Group Laboratories (Torrelavega, Spain) and Cantabria University. Formpave Ltd and the DTI funded the water harvesting experiments. Thank you very much to Irene Martinez, Sandra de Cos and Elisa Di Fant for their special help.
REFERENCES Pratt, C.J., Newman, A.P. and Brownstein, J.B. (1996). “Bio-remediation processes within a permeable pavement: initial observations.”; 7th International Conference on Urban Storm Drainage, IAHR/IAWQ, Hanover, Germany Soxhlet Method. “Extraction of hydrocarbon”; Standard Methods for the Examination of Water and Wastewater, 20th Edition (1998). Pratt, C. J.; Newman, A. P.; Bond, P. C. (1999). “Mineral oil bio-degradation within a permeable pavement long term observations”; Water Science and Technology, Vol. 39, No. 2, pp. 103-109 Dierkes, C., Kuhlman, L., Kandasamy J. and Angelis G. (2002). “Pollution Retention Capability and Maintenance of Permeable Pavements”. ; 9th International Conference on Urban Drainage, Portland, Oregon. 8-13 September 2002. Newman, A.P., Pratt, C.J.; Coupe, S.; Cresswell, N. (2002). "Oil bio-degradation within permeable pavements by microbial communities"; Wat. Sci. & Tech, 45 (7): 51-56 Coupe S.J., Smith H.G., Newman A.P., and Puehmeier T., (2003). “Biodegradation and microbial diversity within permeable pavements”. Eur. J of Protistology, 39 (4), pp495-498 Pratt, C.J. (2003). "Application of geosynthetics in sustainable drainage systems "; 1st International Geosynthetics Society, UK Chapter ‘Geosynthetics: Protecting the Environment’, Loughborough, 17 June Nafiz Korkut, Eyüp. (2003). "Geotextiles as Biofilm Attachment Baffles for Wastewater Treatment"; Thesis of Drexel University. Puehmeier, T., Coupe, S. J., Newman, A. P., Shuttleworth, A., Pratt, C. J. (2004). “Recent developments in oil degrading pervious pavement systems-improving sustainability”; NOVATECH’2004, Sustainable Techniques and Strategies in Urban Water Management, 5 International Conference; Lyon: Graie; ISBN: 2-9509337-6-9, págs. 811-818
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