The wastewater that is produced by lagooning sludge, sewer sludge/storm drain sludge and material collected in sand traps, has to be treated. At the sludge treatment centre (SRC) of Krankeloon, Belgium, two different wastewater streams can be distinguished:
- Lagooning water
- Sewer sludge
Purazur NV was responsible for the dimensioning, construction, delivery and commissioning of a new water treatment plant.
Due to the very different characteristics of both streams, a separate treatment was proposed. The lagooning water is physico-chemically treated, while the sewer sludge is first biologically treated, after which it joins the lagooning water for the physico-chemical treatment.
For the treatment of the wastewater from the sewer sludge, a Sequencing Batch Reactor with a total volume of ca. 240 m³ is used. The batch process consists of the following phases:
2. Aerobic phase: BOD removal and nitrification
3. Anoxic phase: denitrification
An ion-specific measurement of ammonia and nitrate in the sequencing batch reactor (SBR) enables the concentrations to be checked during the process and if there are high levels, it can be used to regulate the duration of the aeration in the reactor for example. The effluent of the SBR, together with the lagooning water, is then pumped to the physico-chemical treatment. This treatment consists of a coagulation/flocculation followed by a lamella separator. FeCl3 coagulant is dosed in a tank equipped with a fast-rotating mixer. Flocculation occurs with liquid polymer in a tank with a slow-rotating mixer. Finally, the water passes through a sand and activated carbon filter before being discharged.