Image for Launceston ... Sewerage systems can’t cope with more extreme weather

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Clogged ... the dredge top and close up of tampon strings, below

Anyone flushing a toilet in urban Australia today does so confident that they’ll never again see the thing they’ve flushed. They probably also think they are causing minimal environmental harm, thanks to our well-designed wastewater treatment plants. But is our lack of concern for sewage pollution well founded? Recents events in northern Tasmania suggest not.

Launceston sits on the Tamar River estuary, in northern Tasmania. Residents have long been concerned about poor water quality and excessive sedimentation in the estuary. A recent study suggests the problem could be solved – or at least ameliorated – by releasing environmental flows from a hydroelectric dam and restoring wetlands to help the tide flush away sediment.

But meanwhile, the local government has decided to rake the Tamar’s silt as a stop-gap measure. This involves dragging a large rake from the stern of a fishing boat, stirring up the fine sediments that are then washed downstream on an ebb tide.

But the raking has brought unexpected consequences: it has exposed the size of Launceston’s sewage problem. Photos taken after a recent raking session on July 7, 2013, reveal a rake clogged with tampon strings. It’s been happening so often the rake operator has had to come up with a novel means of disentangling the strings from his equipment. He takes the rake home and burns the strings off in a fire in his backyard.

Why is there layer of tampon strings on the bed of the Tamar River estuary? The answer lies in ageing urban infrastructure. Launceston was established in 1806 – it is Australia’s third oldest city – and it now supports a regional population of 90,000. The sewage and stormwater runoff from older parts of the city are combined.

During high rainfall the secondary treatment plants cannot cope with the sudden increase in stormwater. So all wastewater (stormwater and raw sewage) is released directly into the estuary.

The old mantra “the solution to pollution is dilution” cannot be applied here: heavy rain does not make things better. Without intervention, wastes will continue to slosh backwards and forwards on the estuary’s tides, continuing to create the problems now so evident on Launceston’s doorstep.

Read the complete article, with full links, The Conversation, here

Last week on Tasmanian Times, Geoff Smedley, This Obnoxious Residue

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