Laying an Egg.
Egg-Shaped Digesters (ESD) at Woodman Point have provided reliable service in the treatment of wastewater for the past 15 years and now the Alliance is building a third to meet the load demands of a growing population.
The unique shape of the ESD provides exciting challenges for the construction crew who look forward to a challenging project that will require considerable planning and co-ordination to build a tank with an 8,000 cubic metre capacity
ESD Project timeline
July – November 2009 - Construct Egg to the equator
November 2009 – February 2010 – Construct Egg to stressing point
February 2010 – Vertical and horizontal stressing
February - Apr 2010 – Complete top of Egg, Construct Sludge Box, precast walkway
April -June 2010 – Mechanical works
What does an ESD do?
Woodman Point uses the high rate anaerobic digestion process to reduce the volume of wastewater sludge produced.
Sludge from the main plant is added in batches to each of the 8,000 cubic metre volume digesters, in which the temperature is maintained at above 35 degrees Celsius. Constant mixing ensures that the micro-organisms present have the best chance of consuming the nutrients within the sludge, producing stabilised bio-solids and methane gas as a by-product.
The sludge remains within the digester for an average of 18 days to ensure that it meets the guidelines for safe disposal. The resultant bio-solids are valued by the agricultural and forestry industry as an excellent soil conditioner.