INTRODUCTION
A significant nutrient load can be generated
internally by publicly owned treatment works
(POTWs). These nutrients can be found in the
reject water, also known as side streams, of
many municipal wastewater and sewage sludge
treatment processes. These side streams include
the reject stream from membranes, supernatant
liquid from sludge digesters, and the
centrate/filtrate return stream from sewage
sludge dewatering processes, among others.
Most of these side streams are conventionally
returned to the headworks of the POTW, where
they are combined with the normal influent.
Estimates of the nitrogen load from this side
stream return are between 15 and 30 percent of
the total nitrogen load on the process (Solley, D.
2000).