How to keep an object unique

Given that the services will at least be using different AppDomains, and quite possibly different processes, sharing the same data between all of them would be tricky.

I would personally suggest that you just don't worry about it - unless each record is actually pretty large, 80K records is still going to be fairly small.

You could potentially have an 11th service which is the only one to have the data, and then talk to that service from the other ones. But that's introducing a lot of complexity for very little benefit.

One way of potentially saving memory would be to use a List<T> for a custom type, instead of a DataTable - that may well be more efficient, and would almost certainly be more pleasant to use within the code. It doesn't help if you really need DataTable for whatever you're doing with it, but personally I try to avoid that...