Generally the only way to avoid this happening everywhere is to seperate surface water and sewage into seperate systems, and discharge the surface water directly into rivers and sea. As the planet warms (slightly) evaporation from the sea will increase, and there will be more rain, and it is impossible for any sewage treatment plant to cope with this amount of water appearing at their inflow point in storm conditions. There must be an overflow of some sort to act as a safety valve. If the treatment plant floods then the problem is massively compounded, there is no effluent grid, all water and sewage treatment is local. Once we have a seperate system, it must be kept clean, and the rivers that it discharges into must be dredged, something which has not happened for a long time!
We had this done in Driffield(Pop 13000) some time ago, it was a massive undertaking. took over a year, and involved a remote controlled hydraulically powered mole about 3ft diameter which drilled from point to point dragging a lining behind it. It was operated from towers built at about 200 yard intervals down the centres of the roads, which had to be closed. In short, disruption and expense on a grand scale. Since this was done, overflow discharges are now very rare, but still occasional.
Rivers and sea can cope with sewage up to a certain point, after all, all the aquatic life craps in it! What it cannot cope with is high phosphate and nitrate agricultural run off, and above all the worst pollutants are the detergents soaps, bleaches and other stuff that pours into the sewer from washing machines, dishwashers, the chemicals needlesly chucked down the toilet, and drain cleaners etc. These kill the bacteria that digests the sewage, and any septic tank owner should know that they can never use these products or their septic tank will stop working in a very short time, and need constant pumping out! Industrial outfalls are largely licensed and monitored to make sure that they are acceptable.
There is no easy answer to this, apart from the government legislating on the water companies to use their profits for upgrades rather than high salaries and shareholder dividends! Renationalising water, power and transport just throws the cost from the private companies onto the taxpayer, because governments have no money!
Phil
Edited By Phil Whitley on 24/10/2021 14:45:07