Operation and feed of fermentation reactors

In Germany, wastewater is polluted with organic and inorganic compounds, e.g. nitrate and ammonium. Conventionally, both substances are broken down in the biological treatment stage of wastewater treatment plants through nitrification and denitrification.  Here, the ammonium is first converted into nitrate, this is then converted into nitrite and then broken down into nitrogen. There is constant research into alternatives for the step of economically complex denitrification in order to save costs and to protect the environment from pollution by degradation products. The use of Annamox bacteria, which oxidize nitrite and ammonium to nitrogen, is very promising here.

Figure 1 shows a two-stage reactor system that simulates the biological cleaning stage of a wastewater treatment plant with Annamox bacteria. The aim is to investigate the optimum operating parameters. So-called nitrifying bacteria are cultivated in reactor 1 (right). These are bacteria that produce nitrite from ammonium. A peristaltic pump supplies the nitrifiers with fresh, ammonium-containing medium. Once they have produced enough nitrite, parts of the medium are fed from reactor 1 to reactor 2 (left) using a peristaltic pump. In this reactor the Anammox bacteria, which metabolize the nitrite with the remaining ammonium to gaseous nitrogen, are cultivated. Both reactors are consistently mixed with an overhead stirrer for better nutrient distribution.

In the working group of Prof. a. D. Eberhard Aust at the Technical University of Nuremberg, Germany, two RZR 2012 control were used for this purpose (current model: Hei-TORQUE Ultimate 400) and two Hei-FLOW Ultimate 600 with SP standard pump head.

Hei-TORQUE Ultimate 400

• Powerful drive for fermentation reactors

• Stirring shaft guards up to 10.5 mm diameter can be used.

• With RS 232 and USB interface for remote control and process documentation

Hei-FLOW Ultimate 600 with SP standard pump head

• Determine precise feed streams from reactors

• With button to activate the maximum speed for quick filling and emptying of reactor systems

• With analog and RS 232 interface for remote control and process documentation