PROJECT DESCRIPTION
BACKGROUND
Surface runoff is generated by rainfall flowing over the earth’s surface. Urban development over recent decades has rendered land increasingly impermeable, as the soils of agricultural lands and woodlands have been replaced by asphalt and concrete. When rain hits these paved/sealed areas, water gathers pollutants that have accumulated on their surface to generate a polluted runoff stream. This type of contamination is known as non-point source, or diffuse pollution. It has an intermittent flow and a heavily polluted first flush runoff stream generated within 30 minutes of a rain event. This often causes flooding during heavy rains, as a result of inadequate or failing urban drainage systems. Uncontrolled discharge of runoff and stormwater in urban watersheds lowers the quality of receiving waters, making it difficult to keep concentrations of priority pollutants (such as heavy metals and pesticides) below levels set by the Environmental Quality Standards (EQS) Directive, and to achieve good status of water bodies set by the Water Framework Directive (WFD). To tackle this problem, Sustainable Urban Drainage Systems (SUDS) are being adopted for the management of runoff and to mitigate the effects of stormwater, in line with the objectives of the Floods Directive.
OBJECTIVES
LIFE DrainRain was to mitigate the environmental impact of runoff in water bodies (coastal, surface and ground waters). At the start of the project, SUDS would only drain runoff water and care needs to be exercised, as infiltration-type SUDS technology may pose a high pollution risk for groundwater bodies. The project took this approach a step further, by coupling SUDS to treatment systems for diffuse pollution, especially making use of photocatalysts in pavements. In particular, the project aimed to design and implement pilot systems of pervious photocatalytic concrete pavements to decrease uncontrolled water runoff and concentrations of priority substances such as heavy metals, polycyclic aromatic hydrocarbons, pesticides and polychlorinated biphenyls, with the aim of complying with Environmental Quality Standards, contributing to the protection of groundwater and the maritime environment. The project would also demonstrate the efficient use of water resources, defined as one of the top priorities of the European Roadmap ‘Maximisation of water re-use in the EU’, and would help to meet the microbiological quality needed for irrigation and other applications, according to the Spanish Water Re-use Regulation.
The pilot runoff sustainable drainage and treatment system would consist of several components:
- A pervious concrete photocatalytic pavement with organic pollutants first treated on the concrete’s surface by the photocatalyst Titanium Dioxide;
- A drainage and distribution system in which water is collected by pipes made from anti-microbial materials;
- A hydrodynamic separator that utilises centrifugal energy generated by the water flowing inside to separate suspended solids and oils (SS);
- A filter that comes after the complete retention of SS by a pre-filter to avoid clogging, heavy metals will be removed by adsorption on support materials, such as activated carbon and lignite; and
- An anti-biofouling storage tank, which has been constructed using anti-biofouling high-density polyethylene (HDPE), for storing the regenerated water in a way that ensures microbiological quality.
The project would demonstrate the system in two pilot plants in Spain with different climates (Oceanic and Mediterranean) to promote its wider replication. One area is 900 m2 of pervious concrete surface area in the seaport of Ferrol (Galicia) and the other in Calasparra (Murcia) covers 150 m2 of road hard shoulder.
RESULTS
The LIFE DrainRain project demonstrated the viability of an innovative sustainable drainage system (SUDS) that increases water infiltration and improves the quality of water runoff. The system thus was shown to be effective way of mitigating the impact of diffuse pollution, while also avoiding water abstraction by re-using the runoff water. This SUDS employs a photocatalytic porous pavement to remove microbiological and organic compounds (polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB) and pesticides), along with an in-situ modular water treatment system that comprises a hydrodynamic separator for solids removal, a filter for heavy metals and remaining organic compounds, and an anti-fouling storage tank to ensure microbiological quality.
The project team demonstrated the DrainRain system in two pilot areas with contrasting climatic areas: a 900 m2 demonstrator in the port of Ferrol (Atlantic Spain) and a 150 m2 pilot in a hard shoulder off a road in Calasparra (Murcia) in the Mediterranean area. The pavement and water treatments at the pilot sites performed well: in Ferrol, the system drained and improved the quality of 1 452 m3 of runoff water annually by removing between 80 and 100% of total suspended solids, 100% of Escherichia coli, 75% to 100% of heavy metals, 80% to 100% of PAHs, and more than 95% of PCBs and pesticides; in Calasparra, the pilot drained and improved the quality of 42.81 m3 runoff water annually by removing between 86% and 99% of suspended solids, almost all E. coli, 68% of heavy metals and between 17% and 72% of PAHs on the road where PCBs and pesticides were undetectable. The resulting reclaimed water has a high potential for re-use in, for example, washing streets and industrial vehicles, firefighting systems and the irrigation of urban areas or agriculture, based on compliance with the relevant national and European regulation on water re-use.
Further information on the project can be found in the project's layman report (see "Read more" section).
