In one of the city's collection areas, contamination rates have risen more than 4 per cent, while in another suburb it rose from 1.68 per cent to 6.14 per cent before dropping back to 3.85.

Gregadoo Waste Management Facility manager Geoff Pym said all suburbs in the council area are recording increases in contamination since the food organics and garden organics system started two years ago.

Although there are some suburbs sorting its rubbish better than others, Mr Pym said they are still finding items such as plastics, over-sized pieces of wood, rocks and bricks and leftover bread still in its plastic bag.

He said one of the challenges is educating Wagga's mobile populations at Charles Sturt University, Kapooka and the RAAF base.

"The way we do things in Wagga might not be identical to what new residents have had as a service previously," he said.

"We know unless we're actually putting the ... information to the front of people's noses then they'll not come across it."

Mr Pym said the initial lock down at the start of the COVID-19 pandemic also resulted in increased levels of waste and contamination.

Worm Tech Carrathool Composting Facility, which processes the city's FOGO waste, has also found sharp objects such as needles, syringes and lancets, as well as pet manures and kitty litters.

It has also found a growing number of pruning shears, which have been accidentally placed in bins when dumping clippings.

Mr Pym said residents need to pay more care and attention to the waste they are disposing of because there is even a reasonable amount of FOGO materials thrown in the red-lidded bin.

"It's in all of our best interests to reduce the amount of contamination in the FOGO waste. It would deliver a saving to the council ... and would mean there's more room for the right things in the collections," he said.

The council has information about sorting rubbish across its three bin system on its website.