Biodenipho™ / Biodenitro™

Reduction in nitrogen and phosphorous levels

The Biodenipho™ process reduces to a minimum the content of nitrogen and phosphorus in wastewater in addition to significantly reducing organic matter (BOD), ammonia and suspended solids.


Phased Isolation Ditch Systems

The Biodenipho™ process reduces to a minimum the content of nitrogen and phosphorus in wastewater in addition to significantly reducing organic matter (BOD), ammonia and suspended solids.


Furthermore, it eliminates odour nuisances as the sludge is stabilised in the process.

The oxidation ditch system consists of an anaerobic tank located before two interconnected biological tanks of equal volumes and a final settling tank. The biological tanks work in an alternating mode of operation and are equipped with aerators, inlet distributors and outlet chambers.


The Bio-denitro™ process was developed by Krüger, a subsidiary of Veolia Water Technologies, in the 1970s as an inexpensive method of treating wastewater that consistently was able to achieve high levels of nitrogen removal. Since then the process has been developed further in order to meet new and more stringent treatment standards.


The Bio-denitro™ is a unique wastewater treatment process developed by Krüger. The process combines functional design with an outstanding flexibility and highly adaptable operation. As a result, the process has successfully been implemented on more than 300 installations worldwide with plant capacities up to 750,000 PE.


Features & Benefits

A characteristic feature of the Bio-denitro™ process is that the interplay of the two process steps (nitrification and denitrification) is time-controlled (or on-line control).

This offers maximum flexibility to the optimisation of the nitrogen removal. Furthermore, the raw wastewater is always introduced to a tank with denitrification which normally eliminates the need for an external carbon source. Consequently, the effluent quality from a Bio-denitro™ system is one of the best that can be achieved today at minimum operating costs.

Today, a number of treatment systems are available based on the Bio-denitro™ process. The systems consist of 2 to 4 process tanks, with or without biological phosphorus removal and with either internal settling or external settling. All of the systems demonstrate the unique advantages of the Bio-denitro™ process.




Construction of a Bio-denitro™ Plant with brush aerators


As a consequence, the volume for nitrification and denitrification can be adjusted to fit the actual conditions. The result is a system with outstanding flexibility that continuously uses the reaction volume in an optimum way allowing for the best possible treatment.


The Bio-denitro™ process can best be illustrated by following the nitrogen removal in one of the process tanks over a full operating cycle from phase A through D.

Naturally, the progression of the phases is optimised for each specific plant during running-in. Furthermore, additional phases than those shown are available in order to optimize the operation even further.

Phase A
The wastewater is led to tank II where it is kept mixed in an anoxic environment. At such conditions the micro organisms are forced to use the nitrate present from the previous phase as oxygen source while they degrade the organic compound and nitrogen is released to the atmosphere (denitrification). As raw wastewater enters the tank, a corresponding volume of water and activated sludge leaves tank II and flows to tank I. In tank I oxygen is introduced (aerobic conditions) leading to a biological degradation of the remaining organic matter and a conversion of the wastewater ammonia content to nitrate (nitrification). In this and the following phase, the treated wastewater flows from tank I to the final settling tank.

Phase B
Phase B is a brief intermediary phase where the wastewater is lead to tank I into which oxygen is introduced (aerobic conditions). Oxygen is also introduced into tank II in this phase. The purpose of this phase is to reduce the content of ammonia in tank II before the wastewater is discharged from this tank.

Phases C and D
These phases correspond to the phases of A and B, except for the fact that the wastewater influent, effluent, and the process conditions in the tanks are interchanged. Once phase D is completed, the operation cycle will start again.



Krüger’s System Based on the BIO-DENITRO™ process

No. of process tanks

Internal settling tank

External settling thank


Without Bio-P

Without Bio-P

With Bio-P


System D

Bio-denitro™ - Double

Bio-denitro™ - Double


System T

Bio-denitro™ - Triple

Bio-denitro™ - Triple


System Q

Bio-denitro™ - Quattro

Bio-denitro™ - Quattro