It goes in to a tank underground at front of the house, the theory is the water goes in to the land and, eventually, down in to the rive. The solids should be decomposed by bacteria and end up the same way as the water. Not been flushed out in 10 years so fingers crossed. You do have to be...
I guess you can't be 100% but the water is almost certainly clean when it gets to our house. Then through a physical pre-filter and a UV filter so in fairness, probably £100 a year on consumables the.
£0, we have a private supply from a spring. It's lovely tasting and great pressure. I will obviously be way less smug when there's a leak and there's no-one to call up and sort it....