Use open loop, but install a suitable pleated filter on the side going into the chiller and figure on checking/changing it based on pressure drop across the filter...
Curious, are you providing cooling for all three homes with this one unit? If so, you might want to install a buffer tank on the chilled water side so that the compressor has a decent run time and does not short cycle.
“A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot.”
― Robert A. Heinlein