Bacterial inactivation and regrowth in ozonated activated sludges

Techno-economic evaluation of ozone-oxidation for sludge reduction at the full-scale. Comparison between the application to the return activated sludge (RAS) and the sludge digestion unit

“…Furthermore, there might be direct effects of ozonation on microorganism activity and mortality rates, which depend on each species and their location in the floc. Previous researches highlighted the potential of ozonation to transform the microbial composition, with a stronger negative effect on the nitrifying bacteria activity, thus impacting the overall performance of the WWTP [22,26,27]. Most of the past studies on the ozone oxidation treatment have focused on the optimization of operational conditions and have been conducted on pilot plants over short experimental periods [23].…”

“…Beside this decrease, a lower percentage of filamentous bacteria was observed at the microscope analyses conducted on activated sludge samples after ozone application. Indeed, it is widely reported that ozone preferably hits the bacteria filaments which extend beyond the sludge flocs; as a consequence, less water is retained, the flocs become more compact and improve their settleability [27]. Furthermore, a release of Extracellular Polymeric Substances (EPS) in the liquid phase can occur, which act as bridges between the smaller size particles [28,29].…”

A multivariate approach of changes in filamentous, nitrifying and protist communities and nitrogen removal efficiencies during ozone dosage in a full-scale wastewater treatment plant

“…The leakage of these soluble substrates results in an increase of soluble chemical oxygen demand (sCOD), nitrogen and phosphorous loading rates in the reactor (Demir and Filibeli, 2012;Sui et al, 2011), producing indirect impacts on microorganisms during ozonation (Yapsakli et al, 2010). These potential impacts are in addition to direct effect of ozonation on microorganism activity and mortality rates, which depend on each species and their location in the floc (Bölhler and Siegrist, 2004;Fall et al, 2017). Previous research (Fall et al, 2017;Isazadeh et al, 2014;Yan et al, 2009a) highlights the potential of ozonation to transform the microbial community, thus impacting the overall WWTP performance.…”

“…These potential impacts are in addition to direct effect of ozonation on microorganism activity and mortality rates, which depend on each species and their location in the floc (Bölhler and Siegrist, 2004;Fall et al, 2017). Previous research (Fall et al, 2017;Isazadeh et al, 2014;Yan et al, 2009a) highlights the potential of ozonation to transform the microbial community, thus impacting the overall WWTP performance. Among these issues, there has been a major concern about the effect that ozone treatment can cause in nitrification processes.…”