I've got the feeling that you're in a university setting, am I correct?
If so, have someone dig around in the chemsitry department and look for a pH reference electrode that you can borrow, and then with a 10 cm length of silver wire (I recommend 99.99% pure silver at 12 gauge or so, not thin wire) you can make yourself a silver ion specific electrode and combined with the pH reference electrode and a digital voltmeter or a pH meter that can read in mV, you can make readings of the wash water for bromide concentration.
PE and I have both made silver ion specific electrodes out of silver wire, glass tubing, and a little epoxy glue. It takes just a few minutes to do. (Making a reference electrode could be fairly easy, but neither of use have done so yet so that's still to be proven how easy it is!)
There's a few tricks like plating the silver wire before use, but we can cover that if you decide to go that route.