Articles & Case Studies

Berson's Closed Vessel, Medium Pressure UV Technology Chosen For Australian Effluent Irrigation Scheme

Posted: Monday 26th January 2009

Berson's closed vessel, medium pressure UV disinfection technology has been selected by Goulburn Mulwaree Council in New South Wales, Australia, for an innovative effluent irrigation scheme. The scheme is one of a number of initiatives by the Council to conserve precious potable water.

Installed by Ted Willson and Sons Ltd and supplied by CST Wastewater Solutions, Berson's Australian distributor, the pressurised, on-demand effluent irrigation scheme uses four Berson InLine UV chambers in two parallel trains of two chambers each. Each UV chamber contains 12 Berson 3.5kW medium pressure multi-wave lamps. The UV system can operate with either one twin train of chambers or both trains together, for flows up to 400 litres per second. A low-flow jacking pump system maintains the irrigation system pressure when there is no demand.

The original construction contract was to pump from the storage lagoon to an in-channel, low pressure UV treatment system, feeding to a second, storage tank. This would be followed by an on-demand pumped irrigation system. After a review, it was decided to opt for a more simple, innovative approach, using a pressurised, on-demand irrigation scheme and closed-vessel, medium pressure UV technology.

Pieter Groenewegen of CST comments: "Until now the Australian water and wastewater industry has been dominated by low pressure, in-channel UV systems, but increasingly designers and end-users are starting to appreciate the benefits of closed-vessel, medium pressure systems. Berson's InLine medium pressure chambers allowed us to simplify the civil works and the whole installation. There have been big cost savings for the Council, with no need for large open channels, additional storage tanks and two pump stations, giving lower construction and operating costs. These savings run into several hundred thousand dollars."

According to Greg Finlayson, the Council's Manager of Water Services, "We were already using effluent for irrigation, but the UV-treated effluent gave the Council more opportunities for reuse, as well as improving the quality of the water that eventually finds its way into the Wollondilly River, which is part of the Sydney water catchment."

Marina Hollands, the Council's Water and Waste Engineer, added, "The UV disinfection system is achieving a good microbial kill rate and the performance of the completed scheme is excellent."

Under the original plans the storage pond embankment would have required significant reconstruction to fit a pump, wet well and large concrete channel for housing the low-pressure UV lamps. The new design did not require the embankment reconstruction or the concrete channel the medium pressure UV units are all in-pipe so have a very compact footprint. The UV system also has many fewer lamps than a low-pressure alternative and is therefore much easier to maintain.

Unlike low pressure UV lamps, the multi-wave, medium pressure UV lamps used in Berson's InLine chambers produce a broad spectrum of UV wavelengths which act on the whole microorganism, rather than just its DNA alone. This provides permanent deactivation by ensuring photoreactivation and dark repair of the microorganisms' DNA cannot occur [1].

[1] It has been shown in independent tests that many microorganisms are able to repair themselves after exposure to UV from low pressure lamps, especially if they are subsequently exposed to sunlight, a process known as photoreactivation. Some can even repair themselves without the aid of sunlight, known as dark repair. (See: Hu J. Y.,Chu, S. N., Quek, P. H., Feng, Y. Y., and Tan, X. L. (2005). Repair and regrowth of Escherichia coli after low- and medium-pressure ultraviolet disinfection. Water Science and Technology: Water Supply, Vol. 5, No. 5, 101-108).

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