Combined Nitrification and Denitrification for Wastewater Treatment in Industry


Biological treatment with nitrification and denitrification from H+E

Compact. Efficient. Stable operation.

Especially in the production of food and beverages, as well as in the oil and gas industry, wastewaters contain medium to high nitrogen loads. BIOFIT®.N is a proven process for nitrogen removal from treated wastewaters.

BIOFIT®.N is used if nitrogen is existent in wastewater in the form of ammonia, organically bound nitrogen or nitrate, which is the case e.g. in the cleaning and manufacturing processes in the food industry. The BIOFIT®.N process achieves this exceptionally high rate of nitrogen removal through its procedural structure. Constructional separation of the nitrification and denitrification process steps increases the efficiency, so that highest removal rates of over 90% can be achieved. At the same time, BIOFIT®.N can be used as an individual process stage or in combination with an upstream selector without additional anaerobic stage.

Process Components BIOFIT®.N

Nitrification stage of BIOFIT®.N with AEROFIT®.D aeration system.
Nitrification stage of BIOFIT®.N with AEROFIT®.D aeration system.

The efficient treatment of nitrogen-containing wastewaters requires both treatment steps nitrification and denitrification.

While the nitrification process requires a lot of oxygen, the denitrification process can only take place in anoxic conditions; to be precise, without dissolved oxygen, concurrently present nitrate, and a carbon source. For this reason, BIOFIT®.N organises these processes separately in two concentric ring tanks. This arrangement leads to a uniform ring-plug flow in the nitrification section, which ensures uniform operation behaviour at optimum efficiency.

The first stage of denitrification, i.e. the reduction of nitrate to elementary nitrogen, takes place in the non-aerated cylindrical inner ring of the activated sludge tank. A large amount of the nitrified wastewater is recirculated into the inner denitrification zone and a submerged mixer ensures its movement. The carbon amount in the inflowing wastewater provides the energy for the nitrate respiration. The wastewater then flows from the inner tank into the aerated outer ring, where the ammonia nitrogen oxidises to nitrate and the remaining carbon is removed.

Due to the cascades in the denitrification and nitrification process a sludge is formed that can be easily separated from the wastewater via sedimentation in the post-treatment. Especially if the reactors are very high, a degassing stage will be placed before the post-treatment to avoid gas release and resulting flotation effects. The excess sludge is fed to the sludge treatment.

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