Process Water Treatment at the Münchehofe Sewage Treatment Plant

Cause

The two new purification stages of flocculation filtration and process water treatment at the Münchehofe sewage treatment plant target the residues of the nutrients nitrogen and phosphorus that have not yet been completely eliminated in biological purification. These nutrients are used as fertiliser in agriculture, but are therefore undesirable in water bodies. The biological process water treatment plant was built for the residual nitrogen. In it, so-called planctomycetes metabolise the nitrogen, which is mainly present as ammonium from the dewatering of the sewage sludge, in isolation from other bacteria in the biological treatment stage.

Process

The centrate ("process water") from sludge dewatering is purified in the PWB. The process water contains high concentrations of ammonium nitrogen NH4-N, which are largely removed using the deammonification process in the newly constructed, two-stage SBR plant (sequencing batch reactor).

The process water from the digested sludge dewatering (centrifuges) is fed into the new covered process water storage tank via the centrate pumping station (existing system) and then fed to the SBR reactors. By setting specific process parameters, it is possible to successfully operate deammonification with suspended biomass. The dry matter content is between 1 - 8 g/l in normal operation.

The following parameters are determined online in both reactors for process monitoring and control:

oxygen content
pH value/temperature
conductivity
Ammonium/nitrate
Nitrite (optional)
Fill level
Foam detection