Modern Rainwater Treatment

Pilot project – Infi ltration basin with fi lter media

The company Interprotect is one of the leading manufacturers of road traffi c safety barrier systems. This year their premises at Laupheim were extended by approx. 3 hectares to provide additional storage space for production, among other things. In a joint operation with the client, together with the Administrative District Offi ce of the town of Biberach and Funke Kunststoff e, the responsible planning engineer developed a modern rainwater treatment concept. Rainwater from the storage areas and roof surfaces fl ows through a pipe system to a basin that measures 300 m2 containing a layer of a sand and lava mixture as well as D-Rainclean Filter Media (Zn). According to all those participating in the project the concept will prove its worth. Construction costs were well within budget, due to the substantially reduced space requirements in comparison with other systems, and therefore meets the client’s request for maximum use of the new storage area. In addition to this, contaminants are removed from the rainwater as it fl ows through the D-Rainclean Filter Media (Zn), leaving it free from residues. The implementation of the concept for the treatment of stormwater on the Interprotect site is a pilot project, according to information of the Water Management Agency based in the Administrative District Offi ce of Biberach. The process method and the technology used are breaking completely new ground. The constraints imposed by the authorities are therefore very exacting. According to the responsible planner of Muffl er consulting engineers, a lot of convincing work was required during the preliminary stages. Whereas the wastewater is connected via sewers to the new wastewater pumping station, for the rainwater drainage system a 5 m wide and 0.5 m deep drainage trench is provided along the northeast boundary of the site. Surface water from a 9 m wide strip along the perimeter road as well as the planned hall of the 2nd construction stage is fed into this trench where it percolates away. The rainwater that does not require treatment – this coming from the roof of the hall of the 1st construction stage, the offi ce building and planned petrol station roof of the 2nd construction stage and the yard areas in the south – is collected via road gullies and a new stormwater conduit and then fed centrally into an infi ltration basin with a retention volume of approx. 500 m3. Here it is allowed to soak away completely. The yard area in the north, measuring 8,532 m2, is used for the storage of galvanised steel parts. During rainfall, zinc may be leached out. The joint concept developed by the construction partners also allows zinc-contaminated surface water to be collected in a infi ltration basin. The special feature of this design is that in the basin a layer of a sandlava mixture is laid as well as a 30 cm thick layer of the D-Rainclean Filter Media (Zn) that cleans the rainwater by passing the layer. The substrate is a development of Funke Kunststoff e and has been used with its original composition for several years now in combination with an infi ltration channel used for the treatment and percolation of contaminated stormwater run-off . D-Rainclean Filter Media accomplishes its exceptional cleaning performance using selected natural minerals with a high exchange capacity and fi ltering eff ect. Synthetic products are not used. Heavy metals undergo diff erent processes in the D-Rainclean substrate: nickel is chiefl y held by sorption, while lead, cadmium, copper and zinc are captured by sorption and precipitation in the Filter Media. Cadmium as well as zinc and nickel belong to the mobile, relatively easy to displace heavy metal group. With cadmium, in particular, a constantly high pH value in the D-Rainclean Filter Media is therefore
very important. In soil, lead behaves in a very limpid way. Similarly to copper, lead is tied up by specifi c absorption processes. Mercury is similarly attached to the organic substances in the D-Rainclean. At higher pH values, chromium is mainly tied up in a complex way with iron ions in very diffi cult to dissolve Cr(OH)3 und Cr2O3. In the infi ltration basin designed as an earth pit at the works premises of Interprotect, a 30 cm thick base layer of D-Rainclean Filter Media (Zn) was laid: involving a quantity of some 180 m3 in all. The depth of the basin from the upper edge of the surface is approx. 3 m. The side slopes were made impervious to water in order to also conduct any precipitation directly into the Filter Media. The water level does not exceed 1.60 m, even during intense rainfall. The precipitation from the yard area in the north of the premises is conducted via 4 HS Pipes of DN/OD 500 mm to the edge of the infi ltration basin and then fl ows around the Filter Media body through a ring pipe that is made up of DN/OD 400 mm CONNEX Pipes. From here the water is evenly distributed via branch lines of DN/OD 200 mm HS pipes. The discharge points are protected by means of nonwoven geotextile and boulders to prevent the Filter Media from being washed out. In the inlet areas of the stormwater pipes that lead to the infi ltration basin there are additionally chamber structures installed with a nominal diameter of DN 2000. There is also an HS inspection chamber installed in the bottom of the basin that enables water samples to be taken for testing the cleaning eff ect of the treatment system. According to the planning engineer these arrangements make it possible to meet the stringent requirements set by the Biberach Administrative District Offi ce. Accordingly, details of the infi ltration basin as well as the method used for cleaning surface water contaminated with zinc were carefully coordinated with the Water Management Agency during each phase of the construction work.
Funke Kunststoff e GmbH,
SiegenbeckstraĂźe 15, D-59071 Hamm- Uentrop,
Phone: +49 (0)2388 3071 0, Fax: + 49 (0)2388 3071 550,

Copyright: © DIV Deutscher Industrieverlag GmbH (24.09.2009)


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