Using an Immersion Whirlpool Chiller, so a pump to recirculate the wort, and accelerate the thermal exchange. Consider a tap water between 24C to 28C (75 to 83F), and an environment temperature of about 26C to 30C (80 to 86F).
To chill about 20L (5 galons), I use only the tap water until I reach about 45C (113F) collecting all the hot water that exists from the chiller to reuse in cleaning.
From 45C I stop the wort recirculation, and I switch the chiller exit to a little repository of about 5L (1 gallon), so I start to recirculate (using an another pump) the same water that exits the chiller and so, I start to add ice to it. The cold water (smelted ice) near 0C (32F) is pushed inside the chiller by a pump.
I never tried to add additives (like alcohol) to reduce the ice melting point and have a water below 0C (32F). I think it isn't necessary, because we need to wait some time to settle the solids in the kettle, after turning off the wort recirculation.
I estimate about of 30L (8 gallons) of water collected (never measured) during the chilling. But, all is reused, so doesn't matter much for me if is 30 or 50L.