The Batemans Bay sewage treatment plant upgrade sees us flushed with success.
Built in the late 1970s, the plant was originally designed to manage sewage – pee, poop and wastewater – for a population of 15,000. A 2012 upgrade raised capacity to 25,700.
With this year's upgrade – assuming a daily load of 175 litres of sewage per person – the plant can now treat the waste of 32,000 people.
So how did we do it? Most obvious is our new clarifier; 32 metres wide, this large concrete tank holds the equivalent of one and half Olympic swimming pools. It accompanies the four existing small clarifiers that were struggling to keep up with holiday-time demands.
The clarifier separates out solid waste, which falls to the tank's bottom to be pumped back to a bioreactor for more treatment. At the same time liquid effluent spills over the clarifier's top weir and flows away for sand filtration and ultra-violet light treatment.
There's also a whole new aeration system for the bioreactors, two large concrete tanks that house the microorganisms that break down the sewage.
Just like us, these bugs need a safe space to feed and breath. Your waste is their meal and our new blowers pipe air to the bottom of the tanks through fancy strip diffusers. These create millions of tiny bubbles, just one millimetre wide, making plenty of surface area for the bugs to access. Even so, because these bugs are lazy and don't like to travel under their own steam, we also use banana mixers – large curved yellow propellers – to mix them up even more.
Ideally, every poop spends 25 days breaking down in the bioreactor before it's pumped out to a digester. Then our new sludge facility sees excess water removed, with the remaining biosolids easily loaded into trucks for offsite use as soil conditioners.
Other upgrades include:
- improved resistance to corrosion using epoxy coatings, odour extraction and controlled flow through the inlet system (up to 580 litres of sewage each second)
- better screening of inorganic material like rocks and rags (you'd be amazed what people flush)
- better access across the facility by improving roads and stormwater control and moving powerlines underground
- sand filter and ultra-violet light upgrades in line with improved effluent re-use (providing consistent onsite water and more over for offsite roadworks and sportsfield watering)
- an additional 40kW of solar panels (boosting the site total to 200kW) and massive 850kVa generator for resilience in natural disasters.
While it wasn't all smooth sailing – upgrading an operating brownfield site is always a challenge, even without the impact of COVID, the ever-escalating costs of the infrastructure boom, and three very wet La Nina years when it poured every time a hole was dug. But now we've got some quality infrastructure, ready for a growing population well into the future while protecting the health of our community and environment. Sometimes you just have to go with the flow.
- This story was first published in Council's quarterly newsletter for residents, Living in Eurobodalla. A printed edition is delivered to Eurobodalla's 26,000 households.
