There are a couple of things to look at.
The chiller is not for the CLO2 production directly but for cooling of the desalinated water. However this is unusual because most RO membranes unless they are the heat sanitisable type used for dairy production typically have a 40-45 degree C limit.
The final decision would have to be very site specific but you might use an evaporative type cooler to achieve the cooling you need for this project. It could be an open cycle once through type unit or perhaps a closed lop unit with a heat exchanger. Raw water chemistry may well dictate this decision. Power would be needed for fans and pumps and for a plant of this size power demand will be considerable. The amount of temperature reduction, water quality, closed loop/open loop , ambient temperature and humidity will all influence the power demand.
Chlorine dioxide generation itself is not particularly energy intensive but will require pumps, mixers , valving and instrumentation, to operate and monitor the system. Without know specifics it is difficult to advise, but you will probably need to generate 600-700lbs of chlorine dioxide per day.
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"