If you are careful you can chill the normal way with no "waste". I am in California where water efficiency is always on our minds. The most water that I put down the drain from brewing is from cleaning because that can't be captured and repurposed. For chilling wort I use a standard immersion chiller, along with a whirlpool to keep the wort moving across the coil. I collect the hottest water in the sink for cleaning with later, then collect water in buckets to use for watering household plants and the vegetable garden It is perfectly clean water. When the discharge water from the chiller drops to the temperature of my tap water, I switch to a closed system that has ice water in a small cooler and a submersible pump to move it through the coil and back into the cooler. There are other techniques also, but the key point is to capture any clean water and use it later. The only water that goes down the drain is soapy or dirty in some form, and that is a small fraction of the total.