Practical applications of pollutant retention and biodegradation devices for stormwater infiltration systems serving impervious surfaces and sites under construction

摘要

A problem associated with pervious surfaces of all types is the reluctance by some developers to make use of them. Another important issue, in a retrofit situation, is the need to improve the sustainable aspect of existing drainage may well not be sufficient to justify ripping up and re-laying large areas of pavement (Stovin and Swan, 2003). Indeed pervious pavements are among the least economic options for SUDS retrofit (Stovin, 2004). These factors defined the need to create a system which could be used in conjunction with new or existing impermeable surfaces and with the flexibility to allow either infiltration or attenuation/further treatment under a new paved surface or to facilitate off-line infiltration for retrofit purposes. It is necessary that the system retains much of the hydrocarbon and suspended solid removal capabilities of a pervious pavement. The system proposed is a potentially attractive pre-cleaning device prior to a sand filter or filter trench or swale. Where space allows, such systems could be constructed either as a continuous trench or at intervals along the boundary of a paved area such as a car park, allowing water to be infiltrated directly into the ground. This can be achieved with minimal disruption to an existing paved surface; allowing conversion to be carried out relatively cheaply. Alternatively, in new build applications, the water can be directed back under the surface into a water-storing sub-base or synthetic sub-base replacement system for either infiltration or attenuation. Utilising this technology in combination with the Permaceptor close-coupled oil interceptor, equipped with the floating mat oil sorbing/biodegradation system, can produce a surface water treatment train with three phases of treatment. The device, which was developed, was based on a kerb drain where, instead of the water being conveyed linearly along the drain, the water would be transmitted perpendicular to the drain into a downstream infiltration or attenuation device via a proprietary oil/water separation system. All installations to date have been achieved using either the close-coupled oil interceptor, formed using membranes within shallow structural modules, or by incorporating standard kerb drains and channel drains modified for the process. However, this device has gone through a series of development stages and the testing reported upon is from an earlier form of the system before the development of the current system, which is much more amenable to mass production. Several practical applications of this device will be reported, as will the latest results on the mass produced model. Further important developments relate to the protection of sites from hydrocarbon pollution during the construction phase. This issue is also addressed.