History of the Tahuna plant
The current Tahuna Waste Water Treatment Plant (WWTP) was built in 1981 and has undergone a number of improvements over the years, although none so dramatic as the current project. With many ratepayers asking why the DCC doesn't spend more money on necessities such as improving wastewater treatment, there is some reassurance to be found in the fact that over $100 million has been set aside for this project.
The process of upgrading Dunedin's wastewater began in the 1950s when treatment of the various discharges into Otago Harbour began. Since the 1990s, the DCC has slowly been ticking off stages in its wastewater treatment improvement plans. In 2000, the DCC stopped discharging wastewater into the Harbour, a practice in place since Dunedin was settled. The next step is the Tahuna secondary treatment plant project.
Assessment of environmental effects
The AEE requires that we show we have looked at many options. A 70-strong working party, including members of the public, DCC Water and Waste staff, neighbours and engineers began work in 2001 and met regularly to discuss the options and associated issues. OUr team produced documentation to explain what they were doing, to ensure all interested parties remained well informed.
The September 2002 AEE findings said that there was to be an upgrade in two stages - the installation of the outfall and upgrade of the plant, and the second to produce disinfected secondary effluent. The outcome will be virtually clear water with most of the bugs killed off. The first stage is nearly complete and the second will be finished in September 2011.
Dunedin City's coastal health
There are always bacteria and viruses in the water off our shores. They occur 'naturally', due to farm runoff and other warm-blooded creatures such as seabirds, seals and possums, and as a result of effluent discharge. What is important is that they and the effluent are monitored.
To determine how much wastewater is contaminating the environment, the DCC tests for indicative bacteria, as they are generally more numerous than other types of micro-organisms. The greater the number of indicative bacteria, the greater the risk that pathogenic bacteria and viruses could be present in seawater.
The processe used to monitor shorelines are explained in the Otago Regional Council document 'Environmental Status of the Near Shore Coastal Environment'.
Last reviewed: 12 Jul 2008 7:25pm
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