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Wairakei was one of the world’s first geothermal stations of its kind when it started operation in 1958. Due to the technology available at the time the station was built, Wairakei draws water from the Waikato River to condense steam after it has been used to generate electricity. Hydrogen sulphide (H2S), the gas that gives geothermal areas their distinctive rotten-egg odour, occurs naturally in geothermal steam, and some of it dissolves into the station’s cooling water, which is returned to the river. Contact built the bioreactor to meet increasingly stringent discharge conditions. It pumps used cooling water at a rate of 13,000 litres a second – enough to fill 45 bathtubs every second – through 378km of pipes buried in 100m lengths under a grassed space the size of a rugby field. DOWNER PROJECT MANAGER CRAIG LINGARD RECKONS HE’S A BIT OF A CLOSET GREENIE – “PEOPLE IN MY LINE OF WORK,” HE SAYS, “TEND TO KEEP ANY ECO TENDENCIES QUIET” – BUT HE’S NOT THE ONLY ENGINEER EXCITED ABOUT THE NEW WATER TREATMENT PLANT AT CONTACT ENERGY’S WAIRAKEI POWER STATION. THE BIOREACTOR, AS IT’S KNOWN, IS THOUGHT TO BE A WORLD FIRST AT THIS SCALE It uses natural bacteria to reduce geothermal contaminants in cooling water before it’s released into the neighbouring Waikato River. Contact, Downer, and consultants Beca joined forces to design and construct the bioreactor; their focus on trusting cross-company collaboration and the big picture led to better design, streamlined construction – and completion on time and just under the $30 million budget. As Lingard and his Contact counterpart Alan de Lima give a tour of the bioreactor, commissioned in June 2012, it’s clear they’re chuffed with what’s been achieved.  With water churning through open concrete canals surrounded by shiny pipes, it might be some sort of riverside water feature – but the bioreactor is a serious piece of industrial plant critical to keeping the ageing Wairakei Power Station in business.  “It’s a great piece of kit,” says de Lima. Lingard: “It’s just cool. It’s simple and that’s what makes it so elegant.”  CRAIG LINGARD DOWNER / IN BLACK & WHITE / 11


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