Adsorptive Schwermetallentfernung
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A naturally occurring material fishes heavy-metal ions out of wastewater

On location IGAS - a service provider in the field of environmental analysis and process development, operate a wastewater treatment plant for purifying the surface water and industrial wastewater occurring on the expansive grounds (12,000 m2 in total).The wastewater treatment process consists of "adsorptive heavy-metal removal by a naturally occurring material" and downstream biological purification by rhizofiltration.

The removal of heavy-metal ions from the surface water running off the grounds was necessary because - owing to heavy-metal contamination of the grounds by neighbouring non-ferrous metallurgical works - the surface water displayed relatively high Zn values, which forbade direct discharge into a small receiving watercourse without prior treatment.

Consequently, a process for "adsorptive heavy-metal removal by a naturally occurring material" was developed and a corresponding plant built. The plant has been in operation for three years, complying with the prescribed discharge values without malfunctions or maintenance. The collected surface water flows up through an adsorber bed from below and is virtually free of heavy metals when discharged. As the throughput volume varies between 10 and 100 m³/h, depending on the amount of precipitation, the heavy-metal input values range from 2 to 12 mg Zn/l.The discharge values are constantly < 0.2 mg Zn/l. The heavy-metal ions As, Cd and Ni are likewise removed down to the detection limit by adsorption.

It was determined in laboratory trials that the adsorbent can collect up to 35% of its own weight in heavy-metal ions. The heavy-metal ions are irreversibly bound in the mineral by the exchange of Ca2+ for Zn2+. The heavy-metal ions can no longer be elutriated from the adsorbent.

Once the adsorbent is loaded to capacity, it is replaced by fresh material and disposed of.This simple and inexpensive method for heavy-metal removal is particularly suitable for:

  • Split-flow treatment of wastewater flows containing heavy metals, in order to relieve the burden on the downstream wastewater treatment plant and possibly improve the cost-efficiency of disposal of the sludge generated there.
  • Use as a supplementary treatment stage downstream of a wastewater treatment plant, to ensure compliance with heavy-metal values subject to compulsory monitoring.
  • Purification of surface water from contaminated areas polluted with heavy metals.

The equipment operates without maintenance, but the discharge has to be analysed from time to time for monitoring purposes. The equipment can be sunk into the ground, eliminating costs for pumping if a natural gradient is present. The material is also eminently suitable as a substrate for wastewater treatment in constructed wetlands. In addition to biological purification, all metal ions are then further reduced down to the detection limit. The biofilm formed is also capable of biologically degrading PCB, PCDF and PCDD contained in the water.


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