The two biggest sources of microplastics are car tires and clothing. If you care about reducing microplastics, you should try to not buy plastic clothing (polyester, nylon, etc.) and instead buy biodegrable fibers like cotton or wool. I don't know what to do about the tire thing except drive maybe drive less?
The snag is that the 'micro' in 'microplastics' means they're too small to reasonably or reliably capture without great expense - even at the industrial scales of sewage treatment plants.
See I thought about this and this is what I figured at first, but then it occurred to me that lint isn't actually microscopic. Some of it probably is, but I bet that the normal, trappable size lint escapes into the lakes via the sewage system and then degrades into microscopic plastics. Could be wrong but if this is true then filtering at the washer, using a mesh similar to the one for the dryer could be a significant help. If the numbers work of course.
Quite possibly. I think I recall something like that, but to be effective this has to be mandated to be included inside the washers themselves, similar to the lint filters in dryers.