Glossary



Process water: centrate, filtrate, or press water

Process water is the liquid phase from dewatering of anaerobically stabilized sludge. Depending on the method of sludge separation, it is referred to differently, e.g. as centrate, filtrate or as press water. For the improved separation of the liquid and solid phases, additives such as polymers or caustic are added.
Process water is heavily contaminated with ammonium nitrogen. The reason for this is that during digestion, the nitrogen bound in the organics is released as ammonium nitrogen. The highly concentrated wastewater is typically contaminated with ammonium nitrogen concentrations of 600-1500 mg/l.
Directly treatment of the process water in the main stream places a high load onto the biology and is costly. To relieve the main biology and to avoid the load shocks due during dewatering, this flow can be separated out and pretreated (see sidestream) before entering the mainstream biology. Process water is usually stored in a storage tank after sludge dewatering, and then subjected to a process such as deammonification in the sidestream. Any solids that are contained in the process water should be separated out in the storage tank so as not to interfere with subsequent processes.


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Typical centrate sample
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