posted on 2013-07-02, 00:00authored byHalis Simsek, Tanush Wadhawan, Eakalak Khan
Photochemical
degradation of dissolved organic nitrogen (DON) in final effluent
of trickling filter and activated sludge wastewater treatment plants
(WWTPs) was studied. Inorganic N, mostly nitrite, was produced from
the photodegradation of DON for samples from both WWTPs. Photodegradable
DON (PDON), biodegradable DON (BDON), and overlapping photodegradable–biodegradable
DON (OPBDON) were determined. BDON was associated with PDON as well
as non-PDON. BDON and PDON concentrations in the final effluent
samples were 4.71 and 4.62 mg N/L for the trickling filter plant and
3.95 and 3.73 mg N/L for the activated sludge plant, indicating that
photodegradation is as important as biodegradation in the mineralization
of effluent DON in receiving waters. OPBDON, which is more problematic
in the water environment because it can be mineralized by light or
bacteria or both, was 3.68 and 2.64 mg N/L (57% and 43% of total DON)
in the final effluent samples from the trickling filter and activated
sludge plants, respectively. The DON fraction that is resistant to
biodegradation and photodegradation was 10% to 20% of total DON.