Stephen J. Coupe

Biodegradation and microbial diversity within permeable pavements

Permeable Pavement Structures (PPS), designed to improve drainage of urban paved areas, have been demonstrated to function as hydrocarbon traps with 98.7% efficiency and as powerful in-situ aerobic bioreactors. A mesocosm constructed like one of these pavements and inoculated with microorganisms with the aim of increasing hydrocarbon biodegradation was found not to retain a viable population of organisms derived from the inoculum, although the protozoan fauna initially increased in diversity more quickly than in an identical non-inoculated mesocosm. The source of protozoan diversity in oil cultures containing different components used in pavement construction, was revealed to be primarily the granite sub-base which contained flagellates, gymnamoebae, ciliates and testate amoebae. Other components only provided cosmopolitan genera such as Colpoda and Heteromita. Biodegradation was facilitated to a similar degree by bacteria or fungi, as demonstrated by inhibition with tetracycline and cycloheximide, respectively. A full microbial community, without inhibition by antibiotics, degraded the greatest mass of oil. Elucidating the role of protozoa assists in fully understanding and optimising the function of PPS in hydrocarbon degradation.

Protecting groundwater with oil-retaining pervious pavements: historical perspectives, limitations and recent developments

Pervious pavements are important systems used for source control in Sustainable Drainage Systems (SuDS), which allow water to infiltrate into hard surfaces and then slowly release it either to a drainage outlet or into the ground. They also remove low levels of pollution from the water by filtration and also by biodegradation of hydrocarbons, which are adsorbed to materials within the construction. Following a historical overview of research in this area, this paper describes an experiment that demonstrates the importance of the choice of geotextile in the retention of day-to-day emissions of oil from parked vehicles and the development and initial trials of an oil interceptor system, which has been incorporated within pervious surface construction. The results indicated that in the early years of the life of a pervious pavement the choice of geotextile has a vitally important impact on its oil-retaining role but that, after several years of silting, the choice may become less important. The results also demonstrated that modified direct infiltration pervious pavement systems, constructed on site from traditional materials and geomembrane, can effectively contain very large hydrocarbon spills.

Performance of pervious pavement parking bays storing rainwater in the north of Spain

Pervious pavements are drainage techniques that improve urban water management in a sustainable manner. An experimental pervious pavement parking area has been constructed in the north of Spain (Santander), with the aim of harvesting good quality rainwater. Forty-five pervious pavement structures have been designed and constructed to measure stored water quantity and quality simultaneously. Ten of these structures are specifically constructed with different geotextile layers for improving water storage within the pavements. Following the confirmation in previous laboratory experiments that the geotextile influenced on water storage, two different geosynthetics (Inbitex and a One Way evaporation control membrane) and control pervious pavements with no geotextile layers were tested in the field. Weather conditions were monitored in order to find correlations with the water storage within the pervious pavement models tested. During one year of monitoring the three different pervious pavement types tested remained at their maximum storage capacity. The heavy rain events which occurred during the experimental period caused evaporation rates within the pervious pavements to be not significant, but allowed the researchers to observe certain trends in the water storage. Temperature was the most closely correlated weather factor with the level of the water stored within the pervious pavements tested.

Stormwater harvesting for irrigation purposes: An investigation of chemical quality of water recycled in pervious pavement system

Most available water resources in the world are used for agricultural irrigation. Whilst this level of water use is expected to increase due to rising world population and land use, available water resources are expected to become limited due to climate change and uneven rainfall distribution. Recycled stormwater has the potential to be used as an alternative source of irrigation water and part of sustainable water management strategy. This paper reports on a study to investigate whether a sustainable urban drainage system (SUDS) technique, known as the pervious pavements system (PPS) has the capability to recycle water that meets irrigation water quality standard. Furthermore, the experiment provided information on the impact of hydrocarbon (which was applied to simulate oil dripping from parked vehicles onto PPS), leaching of nutrients from different layers of the PPS and effects of nutrients (applied to enhance bioremediation) on the stormwater recycling efficiency of the PPS. A weekly dose of 6.23 × 10(-3) L of lubricating oil and single dose of 17.06 g of polymer coated controlled-release fertilizer granules were applied to the series of 710 mm × 360 mm model pervious pavement structure except the controls. Rainfall intensity of 7.4 mm/h was applied to the test models at the rate of 3 events per week. Analysis of the recycled water showed that PPS has the capability to recycle stormwater to a quality that meets the chemical standards for use in agricultural irrigation irrespective of the type of sub-base used. There is a potential benefit of nutrient availability in recycled water for plants, but care should be taken not to dispose of this water in natural water courses as it might result in eutrophication problems.

Laboratory-based experiments to investigate the impact of glyphosate-containing herbicide on pollution attenuation and biodegradation in a model pervious paving system.

An experimental investigation was carried out to determine the effect of glyphosate-containing herbicides (GCHs) on the hydrocarbon retention and biodegradation processes known to occur in pervious pavement systems (PPSs). The PPS test rigs were based on the four-layered design detailed in CIRIA C582. This enabled the pollutant retention capacity of the PPS and biodegradation of retained pollutants by microorganisms to be investigated. The use of test rigs also enabled the impact of GCH on PPS eukaryotic organisms to be studied, by the monitoring of protist bioindicators. Results showed that GCH disrupted hydrocarbon retention by the geotextiles relative to rigs with mineral oil only added, as 9.3% and 24.5% of added hydrocarbon were found in herbicide only rigs and herbicide plus oil rigs respectively. In previous studies, PPS contaminated by mineral oil had been shown to retain 98.7% of added oils and over several weeks, biodegrade this oil in situ. Where GCH was added to experimental models, much higher concentrations of heavy metals, including Pb, Cu, and Zn, were released from the PPS in effluent, particularly where GCH and mineral oil were added together. The source of the majority of the metal contamination was thought to be the used engine oil. The herbicide generally increased the total activity of microbial communities in rig systems and had a stimulating effect on bacterial and fungal population numbers. Although the protists, which are part of the microbial community directly or indirectly responsible for biodegradation, were initially strongly affected by the herbicide, they showed resilience by quickly recovering and increasing their population compared with rigs without added herbicide, including the rigs with mineral oil added to them. However, the presence of herbicide was associated with a decrease in the species richness of recorded protist taxa and a predominance of robust, cosmopolitan or ubiquitous protist genera.

Microbial Ecology of Oil Degrading Porous Pavement Structures

The microbial ecology of any biodegradation system is the fundamental factor that controls both the effectiveness of the ongoing biodegradation process and also the ability of the biodegrading population to maintain stability at times of environmental stress. Studies are reported here which provide both initial information on the ecology of an oil degrading porous pavement system (PPS) and significantly advances our knowledge on the appropriate techniques to study that ecology. A major step forward has been made in the use of molecular biological techniques to quantify bacterial biodiversity and these techniques have shown for the first time the extent to which, despite the fact that a single carbon source is available, the complexity of the microbial population in a model structure increases with time. In fact, the initial commercial inoculum used is totally replaced by a bacterial population selected for the conditions in the structure. The importance of the protozoan population and source of its inoculum is also demonstrated.

Testate amoebae: past, present and future

Records of the testate amoeba fauna of soils have accumulated throughout the 20 t h century from numerous sites on all the Earths continents, ranging from equatorial to polar, with analyses of species assemblages in relation to environmental conditions - especially hydrological. Testates have considerable potential to be used as indicators of environmental change and to give insight into the processes of microbial biogeography and speciation. Small ubiquitous species may have an essential role in the biological succcession as soils develop from mineral substrates. Present knowledge suggests that future research in these areas will be of high value.

Meeting on the Microbiology of Soils, Autumn 2001: Testate amoebae – past, present and future

Records of the testate amoeba fauna of soils have accumulated throughout the 20 t h century from numerous sites on all the Earths continents, ranging from equatorial to polar, with analyses of species assemblages in relation to environmental conditions - especially hydrological. Testates have considerable potential to be used as indicators of environmental change and to give insight into the processes of microbial biogeography and speciation. Small ubiquitous species may have an essential role in the biological succcession as soils develop from mineral substrates. Present knowledge suggests that future research in these areas will be of high value.

Modelling Temperature and Energy Balances within Geothermal Paving Systems

ABSTRACT Geothermal pavement systems are novel to the paving industry. It is the combination of ground source heat pumps and permeable pavements which treats urban runoff and utilises renewable energy for heating and cooling applications. An energy and temperature balance was developed for two experimental geothermal paving systems. The heat fluxes were analysed for a heating and cooling cycle to determine the thermogeological relationship for the systems. A 4th order Runge-Kutta numerical method was developed to model the heat fluxes and energy balance using measured temperature data and other environmental factors such as solar radiation, convection and evaporation heat fluxes for the pavement system. The model was statistically tested for its validity and it can be concluded that the Runge-Kutta technique proved to be an effective and reliable predictive tool.

Design and Validation of a Test Rig to Simulate High Rainfall Events for Infiltration Studies of Permeable Pavement Systems

This paper presents the design and validation of a relatively cost-effective test rig to simulate high rainfall events; such a rig offers a great opportunity for conducting studies (e.g., high infiltration studies) that require high intensity of rainfall on pervious pavements and other permeable systems. The calibration of the test rig, which produced more than 600 mm/h rainfall intensity, was successful. A simple method of using digital photography to capture raindrops and determine raindrop diameter was developed and used successfully to determine the drop size of simulated rainfall by the test rig. Results obtained by this method indicated that the raindrop diameter varied from 0.69–8.97 mm, which was consistent with the high rainfall intensity generated by test rig. Categorization of raindrop size according to Wilson Bentley’s classification showed 1.84, 6.42, 33.95, 26.61, and 31.19% for very small, small, medium, large, and very large drops, respectively, which was considered consistent with the relatively high rainfall intensity generated by the test rig.