Eastern Treatment Plant Tertiary Upgrade Project, Melbourne

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The Eastern Treatment Plant is the largest ozone and UV production facility of its kind in the Southern Hemisphere. Image courtesy of UGL. The upgraded treatment plant has a treatment capacity of about 380 million litres on average and 700 million litres at its peak. Image courtesy of Skinner Engineering. The fabrication and installation of mechanical equipment, steel structures, skids and piping was carried out by Skinner Engineering. Image courtesy of Skinner Engineering. Eastern Treatment Plant (ETP) located at Bangholme, about 35km south-east of Melbourne’s City Centre, was upgraded to incorporate an advanced tertiary treatment plant (ATTP). The project was implemented with an investment of A$418m ($380m). The construction works for the upgrade project commenced in 2010 and were completed in December 2012. The plant was commissioned for operations in April 2013. The project was overseen by an Eastern Tertiary Alliance, a partnership consisting of Melbourne Water, Baulderstone, UGL Infrastructure, Black & Veatch and KBR. The project won the global Water and Waste Water Project of the Year title in May 2013. The ETP, incorporating a secondary treatment process, was officially commissioned in 1975. The plant covers an area of about 1,000ha. The treatment process involves screening and sedimentation to remove litter, grit and sludge, and biological treatment and disinfection with chlorine. It served about 1.5 million people in Melbourne’s central, south-eastern and eastern suburbs, treating more than 40% of Melbourne’s sewage, averaging 360 million litres per day and supplied about 22 billion litres of Class C recycled water per annum. The upgrade was carried out to improve the quality of treated water to Class A, which would be discharged into Bass Strait at Boags Rocks, improving the marine environment, and enable more water to be recycled for non-drinking purposes. The upgraded plant is capable of disinfecting 380 million litres of tertiary treated effluent flows on average and 700 million litres at its peak, on a daily basis. Technology trials spanning about 12 months, prior to the start of the expansion project, were completed in February 2009 leading to the selection of the advanced tertiary process over the conventional tertiary filtration approaches for the upgrade project. The upgrade project site covers an area of 11ha. The tertiary treatment facilities comprise seven buildings spread over an area of about six hectares within the ETP. Construction works for the project involved the installation of infrastructure, including ozone injection and ozone production buildings, biological media filters and ultra-violet light and chlorine contact basins, covered treated water storage basins with ancillary tanks, pump stations, chemical dosing and storage facilities, and internal access roads, pipelines and communication cables. The plant’s tertiary treatment process starts with ozone and biological media filtration to reduce colour, odour and suspended solids, followed by secondary ozonation. Ultraviolet (UV) radiation and chlorine are used for disinfection. The secondary treated effluent enters the advanced tertiary treatment plant through a pump station, in the first step of the process. The effluent is then pumped using two stainless-steel pipes where ozone gas, extracted from oxygen in the air using ozone generators, is added at the entrance of the pipes to reduce colour and odour. The third step in the process makes use of the biological media filtration method, where treated water flows through 32 biological media filter concrete tanks comprising layers of anthracite and garnet. The treated water flows through them to produce filtered water. The water is further enhanced by the presence of certain bacteria on the surface on the filter media, which feeds and breaks down organic compounds and reduces the ammonia content. The sludge formed during these stages is removed using a backwash process, thickened and sent to the existing digesters for conversion into biogas. The wash water is reused by sending it back to the first step in the advanced tertiary treatment process. Step four involves the treatment of water with ozone gas for a second time and sent to concrete channels. Step five involves the use of UV disinfection comprising seven UV reactors. The final treatment process makes use of chlorine to disinfect the water, after which the treated water is conveyed to the outfall pump station. Alchimie assisted Melbourne Water in selecting the design and construction partners for the project. Skinner Engineering acted as the main mechanical contractor for the project. Gearon Civil was contracted to carry out major earthworks and civil works. The civil, structural, electrical, mechanical and piping models, created using AutoPLANT P&ID, ProSteel and 3D modelling, were provided by Bentley. The low-voltage (LV) power distribution and electrical installation works were carried out by O’Donnel Griffin. Trojan and Aquatec-Maxcon supplied the UV disinfection system comprising seven closed vessel UV reactors equipped with Trojan’s patented TrojanUV Solo Lamp Technology. Four WEDECO PDO 7500 ozone systems for the project were supplied by ITT. 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