The 350 ML per d Eastern Treatment Plant (ETP) tertiary facility produces “Class A” water for the city of Melbourne, Australia, which is used for irrigation, dual reticulation and fire fighting.

Combining ceramic membranes with ozonation and allowing ozone residual to contact the membrane surface is well known to control fouling, allowing for higher membrane fluxes. This means that the more robust, longer lasting and higher integrity ceramic material can potentially be used in water recycling in a cost competitive way. This paper presents additional results from a previously reported ozonation/ceramic membrane trial in Melbourne, Australia. The results assisted in understanding the cause of the high fluxes by quenching the residual ozone upstream of the membrane, to isolate its effects on organic species from those on the membrane. Ozone quenching was directly attributed to lost membrane performance which confirmed that ozone has a direct effect on the membrane which contributes to the higher fluxes. Tests to reduce cleaning chemical use (sodium hypochlorite) at high fluxes were also conducted. Sodium hypochlorite consumption generally was not significant, but trading better stability and higher fluxes for reduced chemical use needs to be justified. Ceramic membranes coupled with pre-ozonation exhibit unique properties in water treatment, offering potential advantages such as increased backwash disinfection, as well as higher flux rates or reduced chemical consumption.

Currently guidelines for disinfection of water with free chlorine, while primarily developed for potable water, are often used for virus disinfection of nitrified recycled water of >1 NTU (Nephelometric Turbidity Unit). More information is needed on the disinfection efficacy of free chlorine for viruses in waters of varying turbidity and pH due to significant reuse of treated wastewater of varying quality. In this study, disinfection efficacy in nitrified/denitrified activated sludge treated wastewater was investigated for coxsackievirus B5 (CB5), an enterovirus known to be highly resistant to free chlorine. The required chlorine contact times (CT) values (mg.min/L) for inactivation of CB5 were established in treated wastewater at 10 °C and of varying turbidity (0.2, 2, 5 and 20 NTU) and pH (7, 8 and 9). CTs were calculated to achieve 1 to 4 log10 inactivation. Robust data is presented in support of the chlorine CT values required to inactivate a chlorine-resistant virus in a range of turbidities and pHs in treated wastewaters. The testing method used a conservative approach and the data presented have been used to develop the free chlorine virus inactivation guildelines for recycled water in Victoria and South Australia, Australia.

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