The combined effect of dissolved oxygen and COD/N on nitrogen removal and the corresponding mechanisms in intermittent aeration constructed wetlands

Characterization of Anaerobic Effluent: Seasonal Influence and use of Anammox Process as Post-Treatment

“…The results showed that with a ratio of 0.8 gCODgN − 1 and higher there was a reduction in the abundance of anammox bacteria (estimated by FISH). Wang et al (2020) also showed anammox pathway might have a strong contribution in nitrogen removal routes under lower DO (0.8 mg/L) and lower COD/N ratio (6 and 2) condition. They concluded that DO Subtropical annual seasonality of COD/N ratio and minimum (1.7) and maximum (3.0) values which favor anammox activity according to literature.…”

“…One way to predict anammox process behavior as a post -treatment of anaerobic e uent is by analyzing the COD/N ratio, because this ratio controls the balance between heterotrophic bacteria, ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and anammox bacteria (Chamchoi et al, 2008;Meng, 2018 andLi et al, 2019). Up to a certain limit, the presence of organic matter in the reactor's feeding makes nitrogen removal more e cient, because it simultaneously causes the anammox process and the heterotrophic denitri cation (Du et al, 2015;Langone et al, 2014;Ni et al, 2012 andWang et al, 2020). However, if this limit of organic matter is exceeded, it is initiated a competition between anammox and heterotrophic bacteria, which starts to have excessive growth and leads to reduced anammox activity (Ibrahim et al, 2016;Chen et al, 2016 andLi et al, 2019).…”

“…This ratio range varies from 1 to 6. The ratio value depends on COD in uent concentration (Chamchoi et al, 2008;Ni et al, 2012;Chen et al, 2016 andLeal et al, 2016), dissolved oxygen concentration in the reactor (Li et al, 2019 andWang et al, 2020), sludge retention time (Jenni et al, 2014) and the hydraulic retention time from the previous UASB treatment (Li et al, 2019).…”

“…Despite its advantages, few studies were performed to examine the application of the process as posttreatment of e uents with low ammonium ion concentration and higher COD/N ratio, which are characteristic conditions of the anaerobic treated sewage in tropical countries WWTP (Sanchez -Guillén et al, 2014;Leal et al, 2016;Chen et al, 2016;Li et al, 2019 andWang et al, 2020). COD/N ratio plays an important role when choosing and operating technologies and process for nitrogen removal in a WWTP.…”

“…It signi cantly in uences the fraction of microorganisms that convert nitrogen compounds (Li et al, 2019). In addition, DO concentration should be adjusted according to this ratio (COD/N) in order to enhance nitrogen removal via anammox process (Wang et al, 2020).…”