A combined sewer is one that collects surface runoff in addition to industrial and domestic wastewater. Widely found throughout Europe, this type of sewer can overflow, creating a challenge for meeting the water quality goals of EU legislation, including those of the Urban Waste Water Treatment Directive and the Water Framework Directive. Surface water drainage in dry areas of Spain has been overlooked and considered a secondary component of combined sewers, rarely relevant except during periods of torrential rainfall. This attitude, along with rain patterns which differ greatly from those in countries where the principles of sustainable drainage have been widely implemented, might partly explain the relative lack of sustainable urban drainage systems (SUDS) in Spain. SUDS involve a range of structural components (ponds, basins, swales, infiltration systems) and non-structural responses (cleaning programmes, amended regulations) designed to ameliorate the otherwise degrading effects of older, conventional drainage systems. One of the EUs priorities is to adapt urban areas to climate change by using green infrastructure, such as SUDS (EEA Technical report No 15/2011 - Green infrastructure and territorial cohesion). Furthermore, it is clear that such solutions provide additional benefits such as ecosystem services.
The main objective of LIFE CERSUDS was to improve the resilience of cities to climate change and promote the use of green infrastructure in their urban planning as a means of managing surface water flooding. It aimed to achieve this goal through the development and implementation of a demonstration low-carbon SUDS. The system would consist of an innovative permeable surface with a very low environmental impact, based on the use of tiles with low commercial value.
Specifically, the project aimed to:
The LIFE CERSUDS project successfully designed and produced a ceramic tiled pavement in the Spanish city of Benicssim, highlighting numerous environmental benefits throughout the application and use of this innovative low carbon permeable surface that manages surface water flooding .
During the project, the system received more than 1 000 m3 of rainfall, from which 86% was managed by the system, either through collection for future use (7.8%), infiltration in the ground or evaporation into the atmosphere (78.2%).
In this regard, the system allowed the reduction of diffuse pollution due to the eventual prevention of water reaching the sewage system. Similarly, the rainwater quality was very significantly improved by going through the CERSUDS system, as concentration of solids and salts showed a radical reduction of 80% and chemical oxygen demand (COD) was decreased by 90%. Nitrogen and Phosphorous concentrations were also reduced, as well as hydrocarbons, oils and fats (values below detection limits), avoiding some 95% of pollution mass by the system.
Overall, the project demonstrated an effective way of reducing floods caused by torrential rains, runoff volumes and peak flows that would eventually arrive to the sewage network, integrating rainwater treatment in the urban landscape and protecting water quality. The appearance of runoff was delayed by 45 minutes; and peak flow downstream was reduced by at least 72%.
Moreover, the project created an attractive and safe pavement, reducing the level of slipperiness to a Pendulum UNE-ENV 12633 value of 57, even in rainy weather. Monitoring, during the course of the project, showed that the demonstration site wasperforming well,with high levels of approval among the general public; and notably, the project showed that the use of stocked ceramic tiles - tiles with low commercial value - to produce the cobbles, avoided 11,700 kg CO2 eq. emissions. The project carried out a Life Cycle Analysis and drafted a business plan that acknowledge that the system is more expensive than a conventional one using concrete tiles. However, the ceramic system is more sustainable and is competitively priced compared to more aesthetic and high-quality material, such as granite cobbles. The beneficiaries have therefore committed to commercialising the projects approach after its duration. They estimated the amount of low-cost ceramic material that is available in Spain, Portugal and Italy and have demonstrated the viability of projects replication.
The project team also promoted the implementation of green infrastructures in urban areas.
Training material about SUDS in general and on the specific production and construction of the LIFE CERSUDS solution were produced and presented at several European universities. Finally, the project raised a great deal of interest and has helped promote the inclusion of SUDS in guidelines and regulations at national, regional and local level. The Spanish environment ministry is developing national reference guidelines for SUDS implementation and within this context, its climate change department has included LIFE CERSUDS as one of the practical examples of climate change adaptation that will be incorporated on its adaptation platform AdapteCCa.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).