UV Disinfection Employed at the Moorabool Water Treatment Plant

Barwon Water, the Australian state of Victoria's largest regional urban water corporation, tendered for a USEPA validated UV water disinfection system and then awarded the contract to Fluidquip Australia who supplied the Berson Inline 1000+ USEPA UV system.

Barwon Water provides services to more than 295,000 permanent residents. It oversees 12 major reservoirs and 9 water treatment plants, including the Moorabool Water Treatment Plant (WTP) 45 kilometres north of Geelong. The Moorabool catchment supplies approximately 20% of Greater Geelong’s water supply.

In 2010, Barwon Water tendered for a UV disinfection system to be supplied to the Moorabool WTP. Fluidquip Australia was the successful bidder and in 2011 a Berson Inline 1000+USEPA UV system was installed in the supernatant return line. So why exactly is a UV system required at this point in the process? To explain, a brief (and simplified) description of the process employed at the Moorabool WTP is required.

The plant uses DAFF (Dissolved Air Floatation & Filtration) and disinfection by chlorination to treat the incoming raw source water from the catchment to produce its drinking water. As part of the DAFF process, anthracite and sand filtration media is used to filter the water and this media periodically needs to be backwashed with water to clean the media. So as not to waste this backwash water, it is re-used by pumping it to a clarifier for subsequent treatment. The clarified water, called supernatant, is then sent back to the head of the plant where it is blended with the incoming raw water to be treated by the DAFF and disinfection processes.

The supernatant water can contain a relatively high mix of pathogens initially filtered out by the anthracite filtration media. There is one group of these pathogens which is largely resistant to chlorine – protozoans, most commonly represented by Cryptosporidium and Giardia. Thankfully, protozoans are very susceptible to UV radiation, so as the supernatant returns from the clarifier to the head of the plant, it passes through the Berson UV system, which inactivates any protozoans, which may be present.

As part of the tender specification, Barwon Water insisted that the UV system must be USEPA pre-validated. Validation is becoming increasingly important the world over for water authorities charged with ensuring the drinking water they produce is safe for consumption. The Berson UV system was chosen in the tender process because it was a reputable brand and was evaluated as being economically favourable when compared with other bids.

Dene Denny, Team Leader of the Water Treatment Operations Group at Barwon Water commented, “While we had some initial teething problems when the system was first installed, the system is now operating well. Ongoing communication between Barwon Water and Fluidquip Australia was the key to resolving any outstanding issues. We found the site visit by the Berson support engineer very beneficial.”