How about a solar still to deal with tank water change disposal?  More efficient than just letting the water evaporate, and the reclaimed water could be used instead of RO/DI to mix up new salt mix or dumped in the septic system.  The residual salt/brine would still need to be disposed of outside of the septic system, but there would be a much reduced volume to deal with.
				
			 
				 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		