How can I remove the query string from the url after the page loads?

That is achievable in modern browsers using the history api, but probably isn't the best solution to your problem.

history.replaceState({}, 'some title', '/');

It sounds like you would be better off processing the data and then redirecting to the homepage instead of returning an HTML document directly.

Since you aren't wanting to keep the URL around, it won't be useful for bookmarking, so it is quite likely you would be better off making a POST request.

This suggests that you should be using the POST-Redirect-GET pattern.

As others have said, you can do this using the History API in modern browsers (IE10+, FF4+, Chrome5+). There was no full example in the answers, so figured I'd share my solution, as I just had a requirement to do the same thing:

history.pushState(null, "", location.href.split("?")[0]);

If you are using Modernizr, you can also check if the History API is available like so:

if (Modernizr.history) {
    history.pushState(null, "", location.href.split("?")[0]);
}

You can't do that without reloading the page, imagine if you could put whatever you wanted in the browser address bar? Security fun :)

Although you can now do it in HTML5 (which will only work on browsers supporting it) using the new history API, but realistically, your scenario best warrants a rewrite instead of including that (seems sledgehammer to crack a nut).

As you said you don't need the query string after the page loads, you should really post back, then redirected to another URL after you've finished your processing.