Veolia Water Technologies & Solutions

Ferazur*/Mangazur*/Nitrazur* Removal - Groundwater Purification Systems

Biological filtration to remove iron, manganese, arsenic, ammonia & nitrates from groundwater

Ferazur/Mangazur/Nitrazur is a biological filtration process for the removal of iron, manganese, arsenic, ammonia and nitrates from groundwater sources. The precipitate is removed by using Biolite* “S”, our specially-developed media that requires no replacement. The bacteria remain in the media even after backwashing, allowing continual operation for indefinite time periods.


Ferazur/Mangazur/Nitrazur Technology

Contaminants are found in surface and ground waters at varying concentration levels. Even at low concentrations, these metals can cause a host of problems in water, including metallic taste, discoloration, laundry spotting, pipe scaling, and fixture staining. 

Conventional plants rely on physical-chemical reactions using special media, intense aeration, or chemical oxidation. Disadvantages of physical-chemical processes include the expense of chemical consumption, the frequent need for backwash, limited filtration rates, time-consuming operation and maintenance, and inconsistent effluent quality. 

Advantages of biologic filtration 

  • Naturally occurring bacteria and their ability to rapidly oxidize dissolved metals are key to the Ferazur/Mangazur/Nitrazur processes. 
  • Requires less water for backwashing. 
  • Higher metals retention on the Biolite “S” media allows longer filters runs. 
  • Very low operating costs.
  • Due to rapid biological oxidation rates, Ferazur/ Mangazur/Nitrazur systems are designed at filtration rates up to 20 gpm/ft2 (50 m2/h) - allowing smaller filters and smaller footprint installations. 


  • Ferazur for iron removal 
  • Ferazur for arsenic removal 
  • Mangazur for manganese removal 
  • Nitrazur for ammonia & nitrates removal

How it Works

The Metals Biological Filtration Process

During the process, bacteria attach to the Biolite “S” filter media that was designed specifically for biological removal of metals. Biolite media acts as a support for bacteria, enables high-rate filtration, and does not require periodic replacement or regeneration. The Ferazur/Mangazur/Nitrazur process controls the environmental conditions within the filter, ensuring the development of an efficient biofilm.  

The selected microorganisms oxidize into extremely dense precipitates, enabling three to five times the metal retention when compared to chemically-formed precipitates.  

Arsenic removal is achieved through biocatalytic oxidation and absorption with the iron oxides that are continuously produced in the filter. 

The Nitrazur™ process oxidizes ammonia and reduces nitrates. Ammonia oxidation is achieved through autotrophic bacteria while naturally occurring denitrifying heterotrophic bacteria reduce nitrate to nitrogen gas. 

While providing consistent treated water quality, Ferazur/Mangazur/Nitrazur systems also provide operational flexibility, and backwashes can be performed with raw or treated water. 

The optimal pH, and ORP (oxidation-reduction potential) are required for the correct operation of the biological process. This is achieved through the controlled injection of process air (depending on the raw water pH), which increases the ORP.

For some applications, a pH adjustment is necessary to obtain the proper operating conditions, requiring the injections of an alkaline reagent (NaOH, Ca(OH)2 etc). 

The accumulated iron, manganese, arsenic, ammonia and nitrates must eventually be removed from the filter through regular backwashes using a simultaneous water and air scour. This reduces backwash water consumption and ensures an efficient cleaning of the media. Backwashes are typically triggered based on pre-set values of measured pressure drop through the filter.

The Ferazur - Mangazur impact at the Shrewsbury Water Treatment Plant

The Ferazur - Mangazur impact at the Shrewsbury Water Treatment Plant


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