DE NORA TETRA® Media Filtration

De Nora has more than 50 years of experience and > 1,300 installations providing media filtration solutions to both municipal and industrial markets. A variety of filtration products allows De Nora to customize filter design for optimal performance in a particular application. Common municipal applications include pre-treatment of seawater for desalination, filtration of drinking water sources, and tertiary treatment of wastewater. Industrial applications include both gravity and pressure filtration, with a focus on steel industry applications that require removal of high concentrations of oil and grease and mill scale solids


Easy to Operate and Maintain

Cost Saving

Reliability / Equipment Longevity

Regulatory Compliance

Small Footprint / Compact Design

The filter underdrain is one of the most important components contributing to overall filter performance. DNWT offers two categories of filter underdrains: dual parallel lateral underdrain products including DE NORA TETRATM U, LP, and Anchor-Rite® BlocksTM, and SNAP T® Block systems that provides a unique non-clogging underdrain for heavily-loaded applications. Both types of underdrains accommodate a wide variety of granular media types and sizes that are preferentially configured to provide the benefits associated with a DeepBedTM filtration concept. The underdrains provide excellent distribution of backwash air and water for efficient bed cleaning and low filter operating costs for new or retrofit applications. These underdrains are simple to install, require minimal maintenance, have no moving parts vulnerable to wear, and provide consistent performance over a long life


  • History of proven performance
  • Excellent distribution of backwash air and water keeps filter media clean
  • Suitable to retrofit any air / water backwash scheme
  • Low profile for better filtration performance and longer filter runs
  • Reliably strong resistance to underdrain uplift pressure 
  • Low operating costs and minimal maintenance

Principle of Operation

The TETRA™ LP Block™ underdrain provides  an improved distribution of backwash water  to the filter media  through the use of dual compensating laterals.  Backwash water enters  the primary  laterals and  then  passes through the control orifices into the secondary laterals.

Backwash air is properly distributed by the careful design of the upper control orifices between the primary  and secondary laterals,  providing even air distribution.

Media retention on plates maximize the available filter tank depth. Careful quality control and testing during the plate manufacturing process is used to ensure that the media retention plates prohibit media pass through and provide proper flow characteristics. De Nor should be consulted on the use of media retention plates when lime softening or alum coagulant are used upstream as these are known to potentially plug the plates.


Download Tetra De Nora Brochure