It's been a while since I've worked with produce. If you think about it, you're at the early stages of HACCP, trying to design a process which can work, i.e. you need to find some validation. Your first step I would approach some suppliers and ask what products are available. I'd also have a look at academic papers to see what research has been done.
Off the top of my head, I have known of organic acids being used (including acetic acid) and it does have some benefit. I've only practically used it though (with a rinse step) to be followed by a chlorine wash so I can't guarantee it would work in practice.
Another thing which used to be talked about a lot was simply a lot of turbulent water. Not 100% convinced on that one mind.
One area which might be worth a look though is electrolysed water. This is a bit of a cheat if I'm honest. Basically there are some companies out there who use a brine solution (salt - NaCl in water H2O) and then run a current through it. I think it forms hypochlorous acid in situ (HOCl) which is a very good disinfectant, especially if you've got rid of soiling. You'd have to check with the companies but "officially" you'd just be washing the veg in salt water. Unofficially it's probably not all that dissimilar to using chlorine except it is likely to have far more of the chlorine in a form where it's likely to be effective and much nicer to declare.
