Arsenic and hexachlorocyclahexane (HCHs), substances that are carcinogenic and can cause organ damage, can be filtered out of industrial waste water with bran, which is produced when grain is milled. Fraunhofer researchers in collaboration with GUTec mbH have developed a mobile system with bio-adsorbers using bran. It reduces the amount of arsenic and HCH in water to well below the statutory limit values.

Compounds of arsenic and hexachlorocyclahexane (HCHs) previously occurred above all in the production of pesticides. Pesticides containing HCHs have been prohibited in Germany since the 1980s. Arsenic is still used in the semiconductor and glass industries and pollutes water and the soil in many places. Since HCHs and arsenic are carcinogenic substances and can cause organ damage, very strict limit values apply to their presence in water, soil and the air. Water leaking from dumps and old production sites often greatly exceeds these limit values. Producers therefore cannot dispose of waste water containing HCH or arsenic without pretreatment.

In collaboration with GUTec mbH, the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) has developed a mobile HCH and arsenic treatment system for a large chemicals company. It combines an electrochemical process with bio-adsorbers made from chemically modified bran. “You can get bran from grain mills for a few Euros per metric hundredweight. We modify it chemically and use its hydrophobic properties, so that it can bind the toxic substances“, reports Dr. Manfred Kühn of Fraunhofer IGB.

With the aid of the newly developed system, arsenic can be bound almost completely, apart from 0.004 milligrams per liter, and hexachlorcyclohexane can be bound apart from 0.13 micrograms per liter. Thus, we can reduce the concentration far below the statutory limit values of these pollutants for disposing waste water. In order to use the bio-adsorber a number of times, it is possible to desorb the arsenic and the hexachlorcyclohexane. However, disposal by means of combustion or composting is more economical.

The system is highly flexible as far as the process is concerned: At 2.5 meters long, 1,3 meters wide and 2 meters high, it can be used at different locations. It can be operated continuously fully automatically as well as in batch mode.

The arsenic and HCH treatment plant is already being operated by our client on a semi-industrial scale. Additional systems with bio-adsorbers that originate from the collaboration between Fraunhofer IGB and GUTec mbh have for several years been used successfully to remove heavy metals such as copper, lead, cadmium, zinc and chrome.