Improving nitrification, denitrification and bio-P

Assumptions

Nitrifying bacteria that oxidize ammonium to nitrate grow 15-20 times more slowly than other treatment plant bacteria. It is a challenge to compensate the nitrification process for this slow growth rate and maintain a large population of nitrifying biomass for successful biological nitrogen removal.

One way of attain high concentrations of nitrifiers is to establish them as a biofilm using suspended MBBR™ biocarriers. This concept is applied in the HYBAS™ process for nitrogen removal from municipal wastewater.

Reduction of nitrogen

To obtain the most compact solution as possible, research and development is focused on:

• Optimizing the conditions for nitrification
• Protecting the nitrifying microorganisms from toxic disturbances
• Achieving good nitrification even at low dissolved oxygen concentrations

Reduction of phosphorous

In biological phosphorus removal (bio-P) AnoxKaldnes R&D has been addressing the critical process parameters that involve:

• Organic substrates for the bio-P-bacteria
• Volatile fatty acids (VFA)
• Sludge hydrolysis
• Nitrate as an electron acceptor instead of molecular oxygen