With FERMANOX® water treatment, water enriched with atmospheric oxygen is fed directly into the groundwater-bearing soil layers (aquifers) via the drilled well. There, the groundwater is treated in a purely natural and particularly efficient way.

After a short run-in period, a large, oxygen-rich area with optimal conditions for iron and manganese removal is created around the borehole. At the edge of this area – and thus already at a great distance from the well – a treatment zone (reaction chamber) is created in which iron and manganese are oxidized. In this zone, complex natural treatment mechanisms are activated as soon as groundwater containing iron and manganese enters. The iron and manganese oxides attach themselves to the grains of sand in the soil and form oxide layers. They are now present in a solid, poorly soluble form – and thus have no adverse effect on the quality of the groundwater in the soil. The size of the reaction chamber is determined by the water quality of the groundwater, the hydrogeology of the soil and the resulting infiltration amount of the oxygen introduced.

Inside the borehole, a zone is created that only contains pure, treated water of drinking water quality, i.e. the iron, manganese and ammonium concentrations of the water meet at least the limit values ​​of the drinking water regulations. This drinking water can be extracted and used directly from the well.

Thanks to this experience, FERMANOX^® guarantees the treatment of water to drinking water quality (according to the valid TrinkwV 2001[1]) with regard to iron, manganese and ammonium.

Maximum efficiency – minimum energy consumption

In contrast to conventional methods, the FERMANOX^® system only requires a small amount of oxygen-rich water, which is fed into the aquifers for treatment, since the natural reaction zone in the area surrounding the well is many times larger than the filter volume of above-ground filters.

As a result, the energy requirement for the entire water supply is significantly lower than with conventional water treatment.

No maintenance – just checks!

Since the water treatment in the FERMANOX^® process takes place in the aquifer itself, no regular maintenance is required, just an inspection.

In small FERMANOX^® water treatment systems, the strainer in front of the system must be checked once a year to ensure that the oxygen enrichment performance does not drop due to blockages. Large systems are completely maintenance-free.

No filters, no backwash

In contrast to conventional methods, no above-ground filters are necessary. The water is naturally treated before it is pumped and used – without chemicals or replacement material.

Annoying and expensive replacement and disposal of filter material as well as backwashing of the filters are no longer necessary.

Requirements for the borehole

The basic requirement for using the FERMANOX® process is the presence of one or more boreholes in the loose rock (sand or gravel), because the actual processing takes place in the pores of the aquifer. The boreholes themselves must be created in accordance with the usual technical rules and (if there are several wells) with sufficient spacing and with the shortest possible filter sections. If there are several boreholes, the spacing must be agreed with us.

Raw water quality

There are no application limits for iron or manganese concentrations in the raw water. FERMANOX® is even able to treat extreme groundwater to drinking water level, where the raw water values ​​are many times higher than the limit values ​​of the Drinking Water Ordinance. Demanganization in particular requires a minimum pH value of the raw water, which is lower than with above-ground processes due to the high efficiency of the process – without the addition of chemicals. With higher ammonium or methane concentrations in the groundwater, the treatment effort increases significantly.

FERMANOX^® -Interpretation

• Information on water requirements
• Water analyses of existing wells
• Data on well construction

We will be happy to carry out the necessary water analyses for you using raw water samples. Please send us a water sample for this purpose.

In contrast to above-ground filter systems, underground iron and manganese removal (UEE) uses the aquifer itself in the area close to the well as a reaction space and for the retention of the reaction products. Within the reaction space, the oxygen introduced activates the complex treatment mechanisms. The chemical-physical processes are supported by an autocatalytic effect of the already determined oxides. Microbiological processes also play an important role.

The oxidation of the dissolved iron can be expressed, for example, using the following molecular formula:

2 Fe²⁺ + ½ O₂ + (x + 2) H₂O → (Fe₂O₃ * x H₂O) + 4 H^+[1]

After aeration, conventional above-ground filters mainly produce amorphous, water-rich iron(III) hydroxide (Fe(OH)3) and manganese oxide hydrate (MnOOH) and thus large quantities of sludge that have to be backwashed and disposed of.

Underground, the primary reaction product iron(III) hydroxide is converted into crystalline iron(III) oxide hydrate and manganese(III) oxide hydrate into manganese dioxide (MnO2, “manganese dioxide”). The products form fine coatings on the soil grain surface with high density and correspondingly low volume.[1]

Iron and manganese oxide hydrates deposited on the soil grain lead to a high adsorption capacity for iron and manganese ions in the extraction phase. The oxygen introduced during the infiltration phase reaches the iron and manganese ions adsorbed on the grain surface as it flows through the aquifer and oxidizes them to poorly soluble compounds. Part of the oxygen is adsorbed and is still available for oxidation at the start of extraction.

Adsorption-oxidation model – chemical-physical processes in the reaction space of the UEE (courtesy of Prof. Dr.-Ing. U. Rott).

In addition to iron and manganese removal, the introduced oxygen causes other positive reactions in the aquifer:

• Nitrification of ammonium and nitrite^[2]: Ammonium and/or nitrite in groundwater are nitrified and thus significantly reduced. The conversion always takes place bacteriologically and in the case of ammonium always in two stages. 2 NH₄⁺ + 3 O₂→ 2 NO₂^– + 2 H₂O + 4 H⁺ (+ Energy) by Nitrosomonas and Nitrosocystis 2 NO₂^– + O₂→ 2 NO₃^– (+ Energy) by Nitrobacter and NitrosocystisThe resulting biomass is small and usually of no importance.

• Hydrogen sulphide and the unpleasant smell associated with it are eliminated by oxidation.
• Heavy metals such as arsenic, nickel, etc. can be reduced. Since these substances are deposited in the iron oxidation products, it is necessary that the groundwater has a minimum iron content.^[3]
• When oxygen is introduced into the groundwater, methane oxidizes before iron in the aquifer, resulting in a relatively high biomass formation when oxygen demand is high; a special operating mode is therefore required for groundwater containing methane.

By appropriately designing an underground water treatment system, all of the above reactions take place in the aquifer outside the well structure, through which only pure water flows.