Making the Wastewater Treatment Plant less stinky

The Team from Whangarei District Council

Can you smell the wastewater treatment plant on Kioreroa Road? 🐷

We've got a plan to make it less smelly: covers and odour treatment systems (bio filters) will be installed around the four stinkiest parts of the plant between now and September 2025. What are those 4 parts? Buckle up.

💩 1: the inlet works (where the untreated sewage comes in for treating), screenings bin (where the lumps go, including old barbie dolls and false teeth)

😷 2: the sludge thickener tanks (that reduce the water in the sludge prior to disposal)

🟫 3: the sludge holding tanks (exactly what they sound like)

🐌🐌 4. the snail bin. The water treatment plant has four large trickling filters - large round bins filled with granite rock. The wastewater trickles over the rocks and the algae growing on them. The algae take massive amounts of nutrients out of the wastewater and clean it up. It’s a very robust and natural process, accelerated by engineering and technology.

The algae attract small snails (3mm), which just love the environment in the trickling filter – it is wet and full of food. The snails grow there by the billions. Every now and then, a few snails are swept out with the wastewater and are filtered out before the water goes to further cleaning.

Those “few snails” however, add up to 2-3 cubic metres per week. We put them in our snail bin and empty it weekly. However, this is long enough for it to over-power all the other smells in the wastewater treatment plant.