Is there a lot of demand for sewers?
We'd be in a hell of a mess without them. I'd also regard them as a massive liability, certainly not assets. Many are in poor condition due to Hydrogen Sulfide attack, there is a constant issue with misuse, whilst the demands placed on them is continually rising, with climate change and population increase.
All very well shouting for the water Industry to be taken back into Public Ownership, I think it was rather a clever idea to offload it, (and the associated Liabilities) to the Private Sector in the first place, the problem has largely been, too much money has been taken out and not enough re invested, however Welsh Water/Dyr Cymru operates on a 'not for profit' model and their record is no better than anyone elses.
Bottom line remains, there is no easy fix. It does need to be noted that '
Raw Sewage' is only discharged on rare occasions, and usually that's due to a fault with the infrastructure and/or abuse of the network. Storm overflows are a different situation, what is discharged is heavily diluted, and if there wasn't so much rubbish put down the drains, most would be hardly noticeable, as the watercourse would already be surcharged with surface water running off the roads. (Which will contains oil, rubbish, cigarette butts, and anything else that's been washed down the road gullies...)
A lot of work is going on behind the scenes to provide additional capacity for storm flows, increase treatment capacity and standards at many sites, but without separating every single combined sewer in the land, which would be the biggest Civil Engineering project the Country has ever seen, you are never going to stop Storm Overflows.