In its basic form the process consists of two identical and interconnected process tanks. The system is operated by sequentially alternating the flow and the process conditions in the reaction tanks.
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.
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's 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 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.