Flow within a Blue Nite®

Blue Nite® systems utilize Nexom’s Centra-flo® continuous backwash, upflow sand filters. A carbon source is dosed to the wastewater influent prior to entering the sand filters. In the Blue Nite system, fixed-film heterotrophic bacteria convert nitrates (NO3- and NO2-) to atmospheric nitrogen (N2). The composition of the bacterial population depends largely on the specific type of carbon utilized. Bacteria and solids wasting are facilitated by the continuous backwash of the Centra-flo filter. The media washbox removes solids and excess biomass, which are directed to a reject line. The clean sand then falls by gravity back to the media bed.

How the biological denitrification process actually works

Design hydraulic loading rates to Blue Nite filters are dependent on heterotrophic respiration rates, influent nitrate levels, nitrate variability, dissolved oxygen (DO) levels, and expected range in water temperature. Loading rates can also be dictated by the NPDES permit or local regulatory agencies. Nexom's design parameters coupled with its proprietary control system optimizes system parameters to maintain a healthy, stable biomass for denitrification.

The nitrogen gas produced during operation is primarily released from the process as the media passes through the airlift. Removal of gas in this fashion has several benefits that include: eliminating false readings in headloss, eliminating the need to backwash because of gas entrainment, and eliminating the gas bump or upset gas "burps" due to significant nitrogen bubble accumulation typical in static bed filters.

Fits easily into existing WWTFs

The Blue Nite system is available in several models and configurations. The modular nature of the filters allows ease of system engineering and expansion. The filters are available as freestanding fiberglass or stainless steel tank units or can be configured in multi-module concrete cells. Control systems and smaller filters may be mounted on skid systems for mobility or ease of commissioning.

Centra-flo® Process

Quick question:

Can this system also be configured to remove phosphorus?

Since the same dosing and continuous-backwash mechanics enable Blue PRO® reactive filtration and Blue Nite’s attached growth biological denitrification, the two processes can take place simultaneously in the same tanks for total nutrient removal, with only the Blue Nite’s carbon-dosing system as additional required infrastructure while considering the biological kinetics.

Learn more about the Blue PRO process, or contact us to find out how this capability could impact your plant.