Overlapping Photodegradable and Biodegradable Organic Nitrogen in Wastewater Effluents

Abstract

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.

Abiotic Effects on Effluent Dissolved Organic Nitrogen Along an Estuarine Transect

“…Calculations show that both disinfection methods can significantly (p , 0.05) increase concentrations of LMW-N and decrease concentrations of DON (Table 2). It is likely that UV disinfection results in the breakdown of DON in a similar fashion to the breakdown that occurs during natural UV exposure (Simsek et al, 2013). This study's results differ from that of Sattayatewa et al (2010), which showed no changes in DON concentration after UV disinfection, which could be attributed to low UV dosage and contact time (Simsek et al, 2013).…”

“…It is likely that UV disinfection results in the breakdown of DON in a similar fashion to the breakdown that occurs during natural UV exposure (Simsek et al, 2013). This study's results differ from that of Sattayatewa et al (2010), which showed no changes in DON concentration after UV disinfection, which could be attributed to low UV dosage and contact time (Simsek et al, 2013). If a fraction of DON is converted to inorganic LMW-N as a result of UV disinfection, there will be less DON released into the environment.…”

Transcriptome Changes of Escherichia coli, Enterococcus faecalis, and Escherichia coli O157:H7 Laboratory Strains in Response to Photo-Degraded DOM

“…Photodegradation of the DOM of diverse terrigenous sources has been demonstrated to affect the growth and metabolism of bacteria in aquatic ecosystems (Lindell et al, 1995 ; Scully et al, 2003 ; Anesio et al, 2005 ; Lønborg et al, 2013 , 2016 ; Simsek et al, 2013 ). However, no study to date has provided bacterial transcriptomic or mutational changes occurring after exposure to sunlight irradiated DOM.…”

Activated Sludge – 100 Years and Counting

“…rDON has emerged as a topic of interest for facilities that are required to meet strict effluent TN limits (<3 mg/L), since rDON can represent between 0.5 and 1 mg N/L of the effluent N (Sattayatewa et al, 2010). A fraction of the rDON (up to 10%) can also be converted by advanced oxidation processes such as ozonation or H 2 O 2 -UV treatment to a form that is susceptible to further biological transformation (Simsek et al, 2013). Removal of rDON from AS plant effluent can be achieved using enhanced coagulation and flocculation and activated carbon treatment .…”