Switzerland – High-performance filter system for heavy metal removal from roof run-off waterMay 2009 – Copper and zinc must be removed from run-off waters off of roofs larger than the surface areas specified in the Rainwater Management Guidelines of the Swiss Water Pollution Control Association. The specified metal area is 50 m² if the run-off flows into the ground and 500 m² if the run-off is directed into a receiving system.
Eawag, the Aquatic Research Institute of the Swiss Federal Institute of Technology, several years ago started development of an application-friendly process for removal of heavy metals from roof run-off water. The result was an adsorber system developed in the course of a dissertation consisting of a layer of GFH granular ferric hydroxide which permanently, quickly and efficiently removes copper and zinc from roof run-off water. The system has already been successfully tested on several buildings and has been commercially available since the middle of 2008.
The adsorber system is housed in filter cartridges, the number and size of which are selected in accordance with the copper or zinc surface at hand. The smallest available cartridge is 20 cm in diameter and 40 cm in height and provides sufficient capacity for a zinc or copper surface of 100 m².
A cartridge of this type can be used to remove e.g. copper over a period of up to 2 years with an efficiency of over 98 %. It can be inserted and removed by hand. Larger-sized cartridges with a diameter of 40 cm are also available, serving a roof area of 400 m² per cartridge. They are fitted with mounts permitting removal using simple lifting equipment for refilling with new granulate every 1 or 2 years.
The cartridges are inserted vertically in the prefabricated receiving shaft (see illustration at right) which is equally well suited for integration in new shaft designs or existing shafts. The modular system is highly flexible and can be used with a wide variety of shaft sizes and designs. The receiving shaft for the cartridges is marketed by CREABETON BAUSTOFF AG of Rickenbach / Switzerland. Maintenance services for the system are provided by Aqua Dällikon AG of Dällikon / Switzerland.
Advantages of the New Adsorber System
- Simple and flexible handling and maintenance
- Modular system permits use with any metal surface size
- Extremely high efficiency (> 98%) for removal of copper and zinc
- Achieves effluent copper and zinc concentrations below 25 μg/l
- No chemical alteration of run-off water
- Conforms with strict Swiss water pollution regulations