Batteries in the sewage system - a story of failure of the biology of the treatment plant

🧨 When someone threw in the batteries - and all the sediment went silent

Faucets in the sewer system - Some failures come with a bang. Others - quietly. Like this one. The sewage looked normal. The oxygen was there. The temperature was good. But something... wasn't right.

In the morning, we noticed that sediment does not fall. The surface of the chamber was covered with a thin foam, as if someone had made a latte, only instead of milk - with phosphates. The sensors showed the flow, but biology froze. Literally.

🔍 Looking for the cause

At first we thought it was a load issue. But the parameters were normal. No spikes in BOD, COD, or changes in oxygen supply. Only bacteria... sort of. have stopped wanting to live.

The lab did a quick sediment test. The answer came from a vial: heavy metals. High concentrations of zinc, copper and - the cherry - a trace of cadmium. A toxin for biology. Oxygen was there, but there was no one to use it.

🔋 Where did it come from?

We reviewed the surveillance record of the inlet. The sewage had no other color, but shortly after midnight it appeared Conductivity concentration peak. Typical with industrial discharges or dissolved electronic waste. Probably someone threw away the batteries - Or dropped scrubbers from an illegal workshop.

"It's just a few batteries," said someone who had just killed a million nitrifying bacteria.

⚠️ Side effects

Activated sludge began to age - flocs stopped growing,
Increase in BOD5 and COD at the outflow,
There was an intense smell of hydrogen sulfide - a sign that anaerobic bacteria had taken command,
We had to implement a procedure to regenerate the sludge: inoculation with new biomass, oxygen correction, slow colony recovery.

💡 What are the implications of this?

Dropping a battery down the drain doesn't look like a disaster. But it's like dropping poison into an aquarium - only they're working in that aquarium millions of microorganisms. Each aerobic bacteria is one point in a huge purification system. By killing them - you disrupt everything.

A wastewater treatment plant is not a pipe with a hole in it. It's a living ecosystem. And a living system must be respected - because if it dies, you will be the first to feel it.