Blue Water Technologies, Inc., has expanded its Blue PRO wastewater nutrient removal product line with Blue NITE for denitrification. Blue NITE allows municipalities to meet permit levels for discharge of wastewater by lowering nitrate to less than 3 mg/L. Blue Water has installed seven Blue NITE systems in New England.
High levels of nutrients in wastewater can lead to a degradation of water quality by algal growth and dissolved oxygen depletion. For this reason, dischargers face increasingly stringent permit limits for discharge of nutrients to receiving waters. Blue Water helps wastewater dischargers meet their permit levels by removing both phosphorus and nitrate in the same treatment step. While phosphorus is removed by adsorption, nitrate levels are lowered by a biological denitrification process.
To accomplish denitrification, water is dosed with a carbon source as it enters the Centra flo filter. The water passes upward through the filter media, where nitrate is converted to atmospheric nitrogen by the bacteria. A portion of filtrate passes through a sand washer, carrying contaminants and excess bacteria with it. The washer separates solids, which are directed to a reject line. The clean sand then falls by gravity back to the media bed.
Nitrogen gas is produced during operation and becomes entrapped by the filter media. This gas is carried down with the sand and is released in the sand washer. Some of the advantages of this method of gas removal are: no false readings of headloss; the flow of the filter does not need to be reversed; and the reject stream can be routed back to the head of the plant, adding alkalinity for nitrification.
Blue NITE is currently installed at several locations in the U.S., lowering nitrate levels to 3 mg/L or less. In a current, full-scale demonstration project, Blue NITE has lowered nitrate from 10 mg/L to less than 0.3 mg/L. Concurrently small amounts of nitrite (0.5 mg/L) and ammonia (0.8 mg/L) were lowered to less than 0.015 mg/L each.
The process is able to accommodate high or fluctuating influent nitrate levels. Alternatives to methanol may be used for the carbon source. The process applies to wastewater or groundwater applications. Blue NITE may be run concurrently with Blue Water’s Blue PRO process for 90% or greater removal of phosphorus, achieving total nutrient reduction in the same vessel.
