Dunedin city beaches have been given a clean bill of health, staying open every day in the seven months since the new outfall pipe was commissioned at Tahuna in January. The Dunedin City Council is on the verge of deciding what to do with solid waste as part of designing the next phase of its upgrade work, the $74.3 million secondary treatment programme for the Tahuna sewage treatment plant. Council wastewater and stormwater operations team leader Brian Turner said there had been no change since testing started earlier in the year, with the water quality "fine" from St Clair through to Smaills beach.
Even Tomahawk beach, polluted for more than 100 years by the Lawyers Head outfall, had cleaned up quickly, due to the "high energy" coastline. Dr Brian Stewart, of Ryder Consulting, said the water had been tested 128 times since the outfall was commissioned.
Most testing had been done early on, and was now mostly done when weather conditions pushed the plume from the outfall back towards the beaches. The secondary treatment upgrade will including ultraviolet light disinfection, digestion systems and drying techniques at Tahuna.
Mr Turner said the final decision on what to do with about 4.2 tonnes of dried solid waste each day came down to a choice between drying or incineration, a decision he hoped would be made in the next two weeks. "It revolves around what is the most energy efficient. That's the most important thing."
Composting had not worked in Wellington or Rotorua, as councils there had been unable to "get rid of the product". Dried waste could be used on golf courses, where it was mixed with soil and helped trap moisture, while there was the possibility of producing power from burning. Mr Turner said the planned commissioning date for the secondary treatment plant was late 2011.
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