Ever been about to pour rancid milk down the sink and thought…“Hmm, maybe I shouldn’t…”? What about the tomato passata that’s gone off? Or the water you washed the paint in? Or that pungent oil from a tuna can?

Let’s consider the wisdom – or not – of putting everyday items down the plughole.

Unfortunately, they can cause problems by clogging or damaging pipes, creating health hazards and polluting the environment. And they add to the load on wastewater treatment plants.

All indoor wastewater is carried through the sewer system. Everything flushed down the toilet or drained from the kitchen sink, bathtub, or shower connects to the same pipes within our home.

From there, the water flows into the municipal sewer — the large pipes running beneath backyards or streets — and eventually flows to a wastewater treatment plant. Wastewater treatment plants have large aerated tanks full of bacteria that decompose the organic matter in wastewater.

“Chemical oxygen demand” measures how much oxygen is needed to break down organic matter. Every bit of additional matter – from passata to tuna oil – adds to the load. And a higher organic load requires greater aeration........

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