James
Lord of the Erg\o/s
I can't be sure about how waste water is dealt with in the UK, but here in New Zealand, discharge from washing machines, dishwashers, sinks, showers, toilets all go into the waste-water (sewage) system, where the effluent discharge is treated before water is put to sea / rivers.We use the dishwasher almost daily, washing machine every couple of days or so, shower every day, and use the WC numerous times daily. As do the other houses. All the residue from those activities goes into the water course, every day.
I think the snow foam is a piffling nothingness in comparison to this. When doing a regular wash, I dispose of maybe one to one and a half buckets of well-diluted body shampoo, and two or three skooshes of wheel cleaner per wheel, again, radically diluted by the time it reaches the drains. Again, nothing in comparison to the rest of the gunk coming out of the houses.
It is quite different with our storm-water system, which drains run-off from roads, driveways, gutters and suchlike. Storm water is not treated, and flows directly to sea / rivers. My city council has banned car washing on driveways because they attribute excess algal bloom in rivers and estuaries to car shampoos. We are expected to wash cars on lawns, or in dedicated car-washing stations where waste goes into the sewage system.