Odour complaints relating to the North Head plant operation are an ongoing issue for Manly residents but the issue is much bigger than unpleasant smells
The North Head Plant now serves over one million people using 45 kms of pipeline from Blacktown, and ending 3ksm out to sea - a sewerage catchment of 470 square kilometres.
That puts Manly at the end of the longest ocean outfall in the world.
And yet North Head Wastewater Treatment Plant doesn’t have full primary treatment - only 30% of solids are captured from the inflow to the plant - the remaining 70% of solids are discharged to the ocean.
Re-usable sewerage sludge, or bio-solids, are trucked out of Manly to a disposable facility way out West.
All major sewage treatment plants in Australian States other than New South Wales perform secondary or tertiary treatment before discharging solids to the ocean.
The Environment Protection Authority has been asked to intervene, and work with Sydney Water to achieve pollution reduction in the treatment process with recuperative thickening at the North Head plant, a move supported by Good For Manly.
(Recuperative thickening is a 1967 concept in which a portion of digested sludge is thickened and returned to the digester for further digestion. It is a cost effective way to defer major capital expenditure associated with constructing additional digester capacity.)
Sydney Water identified recuperative thickening as a process operation to increase digester capacity using existing assets for very little investment. The process was implemented at North Head in 2010.
However latest reports show that recuperative thickening at North Head, although not run full time due to plant limitations, has had limited impact with 2015 digester performance reported as being the same as it was in 2009, before recuperative thickening was implemented at the plant.
A consultant to Sydney Water stated:
"… optimal digester performance is an important aspect of odour control measures."
It’s interesting that recuperative thickening at Bondi Wastewater Treatment Plant achieved significant improvements: reducing biosolids production by 22%, increasing biogas production by 20% and reducing hydrogen sulphide generation from biosolids by 80%.
Clearly more needs to be done at the North Head Plant!
Manly Council brokered a public meeting between Sydney Water senior managers and concerned residents in November last year. The problem of unpleasant odours from the plant was the main topic, but many other issues were raised, such as decentralisation of wastewater treatment.
However it became clear that there were no plans for any significant upgrades at the North Head plant.
While follow up meetings with Sydney Water are planned for this year, it’s clear that unless we keep the pressure on, nothing will change. That means minimally-treated sewage will continue to be dumped into our ocean backyard and trucks transporting biosolids will continue to emit biosolids offensive odours plus deodorant in Manly on the journey to the disposal facility.
Do you think this should be allowed to continue?
Candy Bingham, Deputy Mayor, Northern Beaches Council. Background in marketing, public relations & community engagement. Author of five business books. Former Lady Mayoress of Sydney. Aka Candy Tymson.