This paper reports the results of the first experimental investigations car
ried out on the only existing full-scale plant that makes use of the biolog
ical treatment system known as ANANOX(R). This system was first set up by t
he Italian research staff at ENEA (Agency for New Technologies, Energy and
Environment) and consists of two biological stages in series: a two-section
ABR and an anoxic section followed by an activated sludge process. The inv
estigation aimed primarily to assess system performance under uncontrolled
load conditions. In particular, system efficiency was assessed with regard
to carbonaceous and nitrogen compounds in the anaerobic and anoxic phases,
and the role of sulphides in the denitrification process was examined.
The results obtained show the system's ability to ensure efficiency levels
that comply with stringent effluent regulations while also allowing conside
rable savings in running costs.