In many Dutch sewerage systems the sewage is pumped from small villages through pipelines to larger cities. These pressurized pipelines often end up in the pump sump of another pumping-station or in another sewerage system which transports the sewage under atmospheric conditions to the waste water treatment installation.
When the waste water in these pipelines stays stationary for a longer period often sulphurous compounds are formed. At the downstream end of the pipeline, where the sewerage system meets atmospheric, aerobic circumstances, the hydrogen sulphide can be converted into sulphuric acid by micro-organisms.
The above described process(es) can lead to the following problems:
corrosion of concrete caused by sulphuric acid;
odour annoyance caused by hydrogen sulphide and other sulphurous compounds.
A good solution against concrete corrosion developed by HASKONING consists of stripping the sulphurous compounds out of the sewage and eliminating them. The most economic way to eliminate H2S is the use of a biological filter. Measurements carried out at a pump sump show that this type of filter is highly effective in eliminating H2S.
Nevertheless, the installed biofilter did not completely avoid odour annoyance. Therefore the outcoming air after the biofilter was led back into the sewerage system. No complaints occurred anymore.