| Title | Hydrogen Sulphide Removal from Geothermal Power Station Cooling Water Using a Biofilm Reactor |
|---|---|
| Authors | Emily BIERRE, Rob FULLERTON |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | tubular bioreactor, biofilm, hydrogen sulphide, sulphur oxidising bacteria, geothermal, power station, Wairakei |
| Abstract | The Wairakei geothermal power station situated in Taupo in the North Island of New Zealand was commissioned in 1958. Cooling water and geothermal steam condensate containing hydrogen sulphide is discharged from the power station to the Waikato River. Environmental concerns over sulphide aquatic toxicity in the river were key considerations during the discharge permit conditions renewal process which ran from 2001 to 2007. New discharge limits for the power station were proposed by Contact Energy and came into effect in August 2012, requiring the mass emission of hydrogen sulphide in the cooling water to be reduced from current levels of approximately 10,300kg/week to 2,800kg/week, with a further reduction to 630kg/week from 2016. This required a hydrogen sulphide concentration reduction from 1000mg/m3 to less than 60mg/m3 in a cooling water flow of 17m3/s. An innovative tubular biofilm reactor was developed, leading to construction of a full scale plant in 2012. The full scale bioreactor consists of 1890 parallel 100mm diameter x 200m length pipes with a total length of 378km, believed to be the largest tubular biofilm reactor in the world at the time of construction. The paper backgrounds the pilot plant investigations, development of design parameters, construction of the full scale bioreactor and reviews performance since commissioning in August 2012. |