UV Disinfection Technology Supplied to Australian Supernatant Recycling System

Berson (Netherlands) has supplied an InLine+ UV disinfection system to a supernatant recycling system used in the filtration plant of Bathurst Regional Council’s recycling system in New South Wales, Australia.

Supplied by Berson’s Australian distributor CST Wastewater Solutions and installed by TWS (Ted Wilson & Sons) of Blayney, the recycling system recovers and disinfects the filter backwash water at the plant and will help the town conserve its potable water supplies as well and provide substantial water savings over the long term.

Serving a population of about 37,000, Bathurst’s water filtration plant currently has a water treatment capacity of 60,000 m3 per day. The filter backwash water, a by-product of the reverse flushing of the sand filters in the filtration plant, is discharged into the system’s three sludge lagoons, along with sludge from the sedimentation tank. Previously the supernatant from the sludge lagoons was eventually decanted from the lagoons and discharged.

Disinfection of backwash supernatant, which is the clear liquid that collects above the sediment, can recover up to 10% of raw water supply while also avoiding the need for discharge flows into river systems.

The new system involved the construction of a supernatant pumping station to enable the automatic recycling of supernatant from the sludge lagoons into an in-ground well, and then into the first chamber of the rapid mix tank.

The water to be recovered at the present annual water consumption of about 6,000,000 m3 could be as much as 192,000 m3 per year with overall water to be saved estimated to be 13,000,000 m3 over 50 years.

The contractor installed two submersible motor pumps for the pumping station at the in-ground well in addition to an electrical switchboard at the pumping well and other associated equipment, including a level control for the pumps and lifting chains for raising and lowering them for maintenance.

The Berson UV disinfection system was fitted between the pumping station and the rapid mix tank to disinfect the recycled water from the sludge lagoons before returning it to the rapid mix tank. The system fully disinfects up to a flow rate of 0.06 m3 per second and has a variable power control to enable the UV dosage to be adjustable to suit operating conditions. A PLC/SCADA telemetry system was installed to automatically or remotely control the operation of the recycle pumps and the UV system.

According to Michael Bambridge, Managing Director of CST Wastewater Solutions, though the process is not widely used in Australia, backwash supernatant disinfection can help recover up to 10% of the raw supply, which reduces the demand on the water storage system and avoids the need for waste flows into the river system.

Importantly, UV disinfection is effective against Cryptosporidium and Giardia, which could be present in the backwash water. Mr Bambridge adds that the new generation Berson SUMMIT lamps are more efficient than earlier lamps and a have a longer life with Berson’s power control system.

The supernatant recycling project at Bathurst Regional Council was partially funded by the Australian Government’s Water for the Future initiative through the National Water Security for Cities and Towns programme.