The main problems in biological wastewater treatment
The big challenge in biological wastewater treatment (oxidation/nitrification) is the intensification of the natural cleaning process.
Further intensification can be achieved by offering the organisms surfaces (carrier materials) on which they can grow (biofilm formation). Ventilated and submerged fixed bed reactors (FBR) use this approach. In contrast to classic clarification processes such as activated sludge biology, higher bacterial concentrations can be achieved. Membrane bioreactors (MBR) are not suitable here because the immobilized microorganisms require permanently installed growth carriers, which ensure a stable and clog-free process as in FBR.
However, none of the methods mentioned can be used to specifically influence the composition of the biomass and thus the metabolic performance. On the other hand, wastewater contaminated with nitrogen, where the nitrogen content is disproportionately high compared to the carbon content, presents sewage treatment plant biology with an unsolvable task.
These requirements are particularly required for waste water from agriculture (liquid manure, digestate, surface waste water). Because of the saturation of the agricultural areas with nitrogenous compounds, farmers and plant operators lack the options for disposing of this waste. The fertilizer ordinance limits the nitrogen input per area.