5% bleach for 20 minutes (direct contact) will kill just about anything. The only two problems are getting direct contact everywhere (like around the gasket and into cracks, like already mentioned) and then getting the bleach out completely before you make beer in it.So there is really no real way to save this bucket. I have it soaking in a 2/3 water 1/3 bleach solution right now. Ill keep it soaking overnight. I dont think anything could live in it after this.
That's what I do, but watch out for minute colonies of mold growing inside the lid, where condensate can form and the rare surviving spore can bloom. I've seen this happen a couple times.I am making it a habit of storing star san in my fermentation buckets now, circulating it every now and then, so I tend to think that should help in the long run.