Filtering water from the East River? You probably want to make sure that you have a good way to distill water in large quantities. Somehow I don't think the Aqua tablets would help you much on that one! <img src="images/graemlins/grin.gif" alt="" />

Distillation means you're going to need fire. Consider ways to rig a chimney in your apartment (stove pipe leading out a window for example). Understanding ventillation will be very important in your situation.