Background Storm water runoff in urban areas can contain high levels of pollution. The ‘first flush’ of rain is often the most polluted. First flush detention tanks have been successfully tested but the system presents some problems that are not easily solved, such as the availability of space. In addition, these systems require very sophisticated numerical models. Distributed Treatment Solutions (DTSs) offer an alternative but these had not been fully tested. DTS technology removes pollutants from storm water by trapping them directly in the gully-hole or the initial pipe of the drainage network by means of appropriate hydraulic and/or chemical/physical devices. This allows the storm water to be treated before it reaches the drainage tubes. The DTS devices are equipped with filters which adsorb the pollutants contained in the storm water. The system is particularly apt to treat first flush water. Objectives The ESTRUS project aimed to demonstrate the sustainability and cost-effectiveness of existing DTS systems for storm water runoff in harbour infrastructures and industrial sites. In these areas, traditional treatment solutions, such as first flush detention tanks, are too costly or unfeasible due to lack of space. The innovative component of the ESTRUS project consisted of a full-scale treatment solution (hydraulic and chemical/physical) using an approach that had been tested within a laboratory situation. The project research focused on, and compared findings from two methodologies. One approach first analysed the storm water in a drainage system without DTS devices to provide a baseline. A DTS device was then introduced into the drainage systems to assess the difference in pollutant capacity of the water runoff. The LIFE team referred to this approach as a “time shifted monitoring campaign”. Another approach analysed the storm water in two different branches of a large drainage system, only one of which was equipped with DTS filters. Data from both branches of the drainage system were compared simultaneously to assess the difference in pollutant capacity of the water runoff. The LIFE team referred to this approach as a “time concurrent monitoring campaign”. This system allowed the project to analyse and compare the DTS device’s performance against the same type of water runoff as in the baseline, and at the same time. Results Results of the tests showed that the DTS hydrocarbons removal efficiency is relevant in field conditions (range 40-60%) but lower than in laboratory tests (range 50-70%). Solids treatment was identified as a critical aspect, because the solids trapped in the filters can be re-suspended back into new flushes of storm waters. Heavy metals were not filtered because they remained in a solution state, while the metals in a particulate state were filtered but they also gave rise to the same problems of re-suspension. Filters were shown to need to be properly maintained to avoid serious problems and exhausted filters can only be disposed of in special-waste-landfill systems, or by incineration. Recycling options for filters were considered limited to a raw material for heat fuel (via controlled incineration), or transforming them into fuel-oil or gas. The beneficiary concluded that the new technology can be regarded as a valid alternative to the end-of-pipe treatment and could be applied in situations where an end-of-pipe treatment plant cannot be constructed. However, the current DTS systems need to be adapted to suit European drainage systems. Improvements could be gained by providing a preliminary sedimentation of storm waters prior to filtration treatment, in order to avoid re-suspension problems. The feasibility of European DTS systems will also depend on the availability of systems that are built to fit the dimensions of European storm drains. Current commercial systems are designed for American drainage systems. The DTS methodology can be applied to other environmental problems as well, provided decentralised treatment actions are recognised as effective, such as in: accidental pollution on paved surfaces, especially in the case of streets or highways where the collection of large quantities of polluted water is extremely demanding in terms of space; and seawater quality protection for bathing and other recreational purposes, by means of diffused treatment along the coast of the water discharging into the sea from various kinds of outlets.Confirmation of these structural issues led to the LIFE team postponing any cost effectiveness assessment of the DTS. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).