Membrane bioreactor (MBR)

Comparable to the treatment of sewage, the TDL Energie GmbH membrane bioreactor is based on the combination of a biological treatment for landfill leachate and subsequent filtration for the separation of sludge and treated water. Instead of large-scale secondary clarifiers, TDL Energie GmbH uses state-of-the-art and space-saving membrane filtration units to realize the filtration process.

In the biological treatment step, the bacteria inside the membrane bioreactor are responsible for two important process steps:

1. The removal of nitrogen-containing species, especially ammonia (NH₄⁺), which are dissolved in the leachate and
2. the decomposition of all bio-degradable organics.

In the TDL Energie GmbH MBR system, the nitrogen removal takes place in two separated stages: The denitrification and nitrification. In the denitrification, the dissolved nitrate (NO₃^-) is converted to gaseous and non-toxic nitrogen, which then safely escapes the reactor. This reaction depends on the presence of a sufficient amount of carbon-containing molecules and thus an external source, e.g. methanol, has to be added on a case-by-case basis.

To minimize or even avoid the consumption of external c-source, it can be beneficial to operate the MBR with the denitrification as the first reactor (upstream denitrification). Organic compounds already present in the raw leachate can be used for a (partial) reduction of the nitrate and therefore might reduce the running costs for chemicals.

In the second process step, the ammonia-rich leachate is treated in the so-called nitrification, where the bacteria transform ammonia nitrate using gaseous oxygen. Additionally, remaining low concentrations of bio-degradable organics are decomposed to water (H₂O) and carbon dioxide (CO₂). The now nitrogen-rich sludge/water mixture is returned to the denitrification for further nitrate removal by formation of gaseous nitrogen. Due to the synergy effect of carbon-removal by the upstream denitrification, the downstream nitrification needs less oxygen, resulting in a lower energy consumption.

To apply the specific treatment plan to your respective landfill leachate and location, the TDL Energie GmbH membrane bioreactor is based on a modular construction suitable for every kind of contaminated water.

Landfill leachate contains a high amount of nutrients used by the bacteria in the activated sludge to grow. The so-called surplus sludge has to be constantly removed from the system for the secondary treatment using dewatering techniques. TDL Energie GmbH’s approach for the separation of sludge and water is the implementation of well-established and reliable ultrafiltration units.

Ultrafiltration is a physical separation technique, where the flow of the sludge/water mixture is perpendicular to the membrane surface. Due to small pore size, particles down to a well-defined threshold size are prevented from passing the membrane surface. In contrast to secondary clarifier tanks, the ultrafiltration guarantees a complete retention of the bacteria and thus increases their concentration within the membrane bioreactor. Simultaneously, the slower growing microorganism have more time to adjust to the specific leachate. The increased degradation efficiency reduces the necessary retention time in the corresponding biology tank, which allows for a space-saving overall design.

All non-biodegradable components passing the membrane can be removed using additional filtration techniques such as activated carbon adsorption or nanofiltration. The result is a discharge water of highest quality and purity.

For every leachte, TDL Energie GmbH will install the appropriate filter combination based on our broad spectrum of suitable filtration techniques. Additionally, the membrane bioreactor plant is remote monitored from a control room by smart automation using SPS, simplifying the operation and reducing the required manpower.