Free Chlorine Disinfection of Full‐Scale MBR Effluent to Achieve 5‐Log Virus Inactivation

Abstract

A series of full-scale testing was performed at the City of Lathrop Consolidated Treatment Facility to determine the "concentration times time" (Ct) value for free chlorine disinfection of nitrified membrane bioreactor (MBR) effluent to achieve more than 5-log virus inactivation. The full-scale testing consisted of tracer study, chlorine decay study, and virus seeding study. The virus seeding study was performed at a flow rate of 1 million gal/d (3800 m3/min), which corresponded to a theoretical contact time of 117 minutes in the chlorine contact basin. It was found that Ct values as small as 3 mg·min/L were sufficient to achieve 5-log inactivation of MS2 bacteriophage in this study, which is comparable to the results of previous bench- and pilot-scale free chlorine disinfection studies on nitrified MBR effluent (3 to 40 mg·min/L), as well as those of pilot- and full-scale studies on granular media-filtered nitrified effluent (2 to 22 mg·min/L).

Ensuring microbial water quality for on-site water reuse: Importance of online sensors for reliable operation

“…Chlorine disinfection is used to inactivate pathogens from the wastewater and to provide ongoing protection against regrowth of pathogens by maintaining a chlorine residual in the reclaimed water. In the presence of ammonium, free chlorine (uncombined chlorine in the form of HOCl or OCl − ) will rapidly form chloramines, which also act as disinfectants, but are much less effective than free chlorine ( Ikehata et al, 2018 ). At high ratios of chlorine to ammonium, chlorine is consumed at a ratio of 7.6 mg of chlorine per mg of ammonium ( Pressley et al, 1972 ), implying that even small variations of ammonium concentrations result in large variations of the chlorine demand.…”

Membrane processes

“…The tracer study, chlorine decay study, and virus seeding study have reported at full‐scale testing a nitrified MBR to achieve more than 5‐log virus inactivation (Ikehata, Li, Komor, & Gibson, 2018). The concentration–time (Ct) value for free chlorine disinfection in the effluent can be as small as 3 mg min/L to be sufficient to achieve 5‐log inactivation of MS2 bacteriophage.…”

Sensor setpoints that ensure compliance with microbial water quality targets for membrane bioreactor and chlorination treatment in on-site water reuse systems

“…Today, membrane bioreactors (MBRs) are increasingly used as a barrier in on-site water reuse systemsespecially in small-scale systems with fewer than 50 people equivalentand are considered a best available technology (Branch et al, 2016;Lesjean et al, 2011). Disinfection of the water is mostly achieved through chlorination, due to its broad-spectrum efficacy and low cost (Ikehata et al, 2018).…”