Various types of wastewater occur on farms. A classic wastewater is the surface water on biogas plants. Milkhouse wastewater or silage seepage can also occur. All of this wastewater can be processed excellently in the FlexBio treatment plants. In addition to conductive water, you receive biogas which you can use directly for energy.

an aerial view of a biogas plant


The organic pollution of the wastewater is between 200 and 15,000 mg / l COD (chemical oxygen demand). Silage seepage can even reach COD values of over 100,000 mg / l. The FlexBio wastewater treatment systems can effectively clean up low loads as well as very high loads and are stable against hydraulic and organic fluctuations.

According to the current status, the wastewater is often brought into the digestate storage facility or spread on agricultural land. In the latter case, the Fertilizer Ordinance must be observed. In practice, it has also been shown that the treatment of the wastewater on the farm is the most suitable solution, as this saves extraction and storage costs. The compact FlexBio container units clean the waste water that occurs to a direct discharge quality.

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a green container system from FlexBio Technologie GmbH in front of a biogas plant
a digital measured value display
Wastewater / seepage water treatment in biogas plants

Technology in practice

The specially developed process for cleaning wastewater from agricultural operations enables an effective reduction in organic pollution in wastewater. The process is characterized by a compact and robust design as well as low energy consumption. After the treatment, the water can be returned to the natural cycle without affecting the quality of the water. The biogas obtained from the organic material can be used to generate energy.

In the first step, the organically contaminated liquids are effectively used in a compact fermentation system (fixed bed fermenter). A packed bed in this fermenter greatly increases the surface area, which serves as a colonization surface for the microorganisms. The fixation of the microorganisms prevents floating and a very effective breakdown of the organic matter can be achieved with dwell times of less than a day. The fermenter can be operated both mesophilically and psychrophilically. Like conventional biogas plants, the fermentation plant produces biogas from the organic matter. In addition to the elimination of organic impurities, nitrogen compounds are effectively broken down in the second step. Under aerobic conditions, in an activated sludge tank downstream of the anaerobic stage, ammonium is nitrified, sometimes denitrified, and another COD is eliminated. A partial flow from this stage is returned to the anaerobic fixed-bed fermenter. The simultaneous loading of organically contaminated wastewater leads to denitrification under anaerobic conditions and thus to the breakdown of nitrate into gaseous nitrogen.

With the FlexBio process, farms receive an environmentally friendly, economical and flexible solution for dealing with their wastewater. By using the biogas potential from the wastewater (at Ø 5,000 COD mg / l up to 2 m³ methane per m³ wastewater), significant amounts of biogas can be obtained. On the other hand, the purification of the wastewater eliminates the need to transport or discharge the water. This leads to the avoidance of climate and environmentally harmful emissions, as well as a reduction in the volume of road traffic in rural regions (environmental relief).

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Close-up of a technology device from FlexBio Technologie GmbH

Measurement and control technology

The FlexBio treatment systems are equipped with the latest control and measurement technology and designed for autonomous and fully automatic operation. Continuous measurements of relevant parameters as well as an intelligent PLC control guarantee optimal utilization of the system and reliable compliance with the limit values. All settings and functions can be made both locally and remotely using any smart device (via a secure VPN access). The feeding of the system is controlled according to the filling level in the collecting basin. In addition, the organic pollution of the wastewater is recorded using measurements. The treated water can then be discharged, infiltrated or rained down as required. The technical components and control elements required for the process are located in a separate machine room. In addition, the container has a status display (green, yellow, red), an emergency switch on the outside and a gas overpressure safety device.

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a COD diagram
a COD diagram

Cleaning performance

The figures show the measurement parameters of a reference system in southern Lower Saxony. Using these graphs, the cleaning performance of an AFBB-010 system (20ft container) should be presented as an example. The diagrams show the organic load (COD) in the input and output of the system.

In order to demonstrate the flexibility and resilience of the cleaning system, 150 meaningful days were chosen. During this period, the system was charged with highly polluted silage seepage water (highlighted in gray) for about 40 days and with less polluted surface water (highlighted in black) from the rainwater retention basin for the remaining 110 days. The input load varied between approx. 100 mg / l COD and approx. 45,000 mg / l COD. Despite the strongly fluctuating exposure, no more than 108 mg / l COD was measured in the COD output and the limit value of 120 mg / l COD was not exceeded. The average throughput is 11 m³ / d in the specified period.

Based on the measurement and the associated intelligent control, the optimal operating performance is continuously set. Due to this permanent adaptation, on the one hand large quantities with low pollution (e.g. heavy rain events) and on the other hand small quantities with high pollution (e.g. silage seepage water) can be treated fully automatically and effectively. In addition, the modular structure of the wastewater treatment systems means that additional modules can be added at any time.

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Ein Portrait von Karsten Wabnitz vor einem grauen Hintergrund mit quadratischen Maßen

Karsten Wabnitz

Technical Sales

+49 5561 – 980 90 70