Hand washing – mildew, mold, smell?

Hi, in one of the places where I live there is currently only hand washing, no washing machine.

So wash in a plastic bowl or in the sink .

Something I only noticed after some time: I once had a few things that started to smell, possibly due to mildew. I learned from my mother and other older people that mildew is almost always black mold. Is that true?

The problem I have now: when I put "freshly soiled" laundry into the plastic tub – and for the reasons mentioned above, I only handwash one item at a time, so only 1 T-shirt, only a pair of socks, only one pair of underwear, etc. because I don't want anything I wash together to have black mold / invisible mildew stains and then transfer that to the other laundry.

Recently, however, I have noticed that when I have washed laundry in several wash cycles, in the last wash cycle, i.e. when it has been left in clear water for a longer time – not for days, but only for a few hours – previously fresh and clean smelling laundry – because it was freshly washed, even if still wet – starts to smell exactly like the laundry from months ago, which I suspect was caused by mildew or black mold.

I rinse the wash bowl thoroughly after every wash (e.g. after the current T-shirt, a pair of socks, etc.) before I start with the next item of hand washing.

Is it possible that black mold has settled invisibly in the plastic washing bowl, and when warm water, soap and the laundry are added, the mold can multiply and, although invisible, also causes the smell that was not present in the dirty laundry, and the smell only comes at the end in the quasi-rinse cycle?

Do I have to throw away the plastic bowl, or would an anti-mold treatment be sufficient, which should not damage the plastic.

70% alcohol or 10% hydrogen peroxide are probably too harsh for household plastic, although both are very effective against black mold. (Currently, I only have hydrogen peroxide at home.)