2mW zb module and wifi gateway: need help with increasing distance

I bought a pair of 2mW zb modules with wire antenna from Sparkfun. I have one connected to my pc the other to an arduino. I can only get 10 ft distance indoor and about 30 ft. in my yard. I’d like to add a wifi gateway. Since the gateway has a pro module inside would I get a better distance between the gateway and the 2mW modules? I need about 100 meters (in a waste water treatment plant).

Try first just changing channels on your XBee ZB modules. Also make sure that the wire whip antenna is perpendicular to the PCB and that the connection has not been broken. That should help with your range issues unless there is something in between the two.