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 TETRATM LP BlockTM dual parallel lateral underdrain from De Nora is a proven design of filter underdrain offering superior distribution of both backwash air and water, either sequentially or concurrently. The TETRATM LP BLOCKTM underdrain ensures lower operating costs and effective backwash distribution that can improves run time.

Effective media cleaning is the key requirement for a filter to function efficiently under all loading conditions. Backwashing gravity filters is necessary to remove the solids collected by the media during the filtration run. The use of concurrent or sequential air and water significantly reduces the volume of dirty backwash water produced and drastically lowers operating costs through the uniform backwash process.


Benefits Of Tetra De Nora

  • Excellent distribution of backwash air/water- more efficient bed cleaning and reduced filter operating costs
  • Wide profile design means approximately 1/3 less laterals and thus fewer joints and grout are required and reduced installation costs
  • Easy maintenance, long life and simple installation
  • Easy retrofit of existing shallow filters with air/water backwash and/or greater media depth
  • GroutGrip design offers increased adhesion to filter floor
  • Easy to install in retrofit applications
  • Dual air/water backwash uses significantly less water than water alone
  • Media retention plate prevents media from entering the block, and also simplifies media replacement
  • Low profile reduces the filter box depth for added savings on new construction

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