Biological denitrification

Biological denitrification

Denitrification is the biological process of converting nitrate and nitrite into nitrogen gas. It is a two-stage process executed by heterotrophic bacteria. These bacteria are using nitrate and nitrite to convert a substrate (typically a carbon source) into nitrogen gas as part of the dissimilation process. The process takes place under anoxic conditions. For tertiary biological denitrification the bacteria are normally using an external carbon source (e.g. methanol, ethanol, acetic acid) as the organic soluble BOD levels – which may be used as well – are mostly low in concentration in the tertiary filter feed.


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We are operating a big tertiary filter plant consisting of 24 filter cells to remove nitrogen and phosphorus prior to effluent discharge. The plant is in operation since 2009, and in the beginning we tried to monitor the filters by using an ultrasonic sand circulation measurement tool. This did not work. After Brightwork implemented Sand-Cycle in 2016, this proved to be very useful in our day-to-day operations. We have managed to operate the filters in the most optimal way and we are very happy to use such a powerful tool.

Jan Boonstra

Wetterskip Fryslân

Conway Engineering were engaged by the Client to design, build and commission a turnkey solution for the treatment of contaminated leachate from dredging operations at Alexandra Basin, Port of Dublin, Ireland. The key challenges included the level of contamination, the onerous discharge standards, the site area available and the limited sampling data initially available for design.

The open collaborative approach with Brightwork allowed us to design and develop a bespoke treatment process that was optimised and extended on site to ensure compliance with the strict environmental licensing in place. This partnership resulted in successful delivery of the Client’s brief to the highest standards

Jennifer MacNamara

Conway Engineering