The name Chris Whitty will forever be associated in people’s minds with Covid-19. But in a recent cri de coeur he reminded us not only that he continues to exist following the end of his daily appearances on our TV screens, but that there are many other ways in which pathogens are out to get us. In a newspaper piece written with the chairs of Ofwat and the Environment Agency, the Chief Medical Officer raised the subject of Britain’s filthy rivers. While Britain’s environment has improved in many ways, with cleaner air, more trees and some species returning after centuries’ absence, our rivers have defied the trend, being more afflicted with sewage than ever before.

‘One of the greatest public health triumphs of the last 200 years was separating human faeces from drinking water,’ began Whitty. Quite so. We take it for granted that when we turn on the tap for a drink of water, we are not going to give ourselves cholera, typhoid or any of the other water-borne diseases which used to carry off large numbers of people in early 19th-century Britain. The infrastructure which keeps our drinking water safe is largely unseen, but no less impressive for that. It cannot be taken for granted – and lamentably still does not exist in many parts of the world.

Unfortunately, while we can be confident of not encountering faeces in our drinking water, the same is not true when we go canoeing or wild swimming. Last year there were more than 300,000 ‘spill events’ in England – occasions when sewage is discharged into rivers and the sea. As well as detracting somewhat from the fashionable activity of wild swimming, sewage discharges can be lethal for wildlife, obliterating all other efforts to encourage nature. On the River Lim in Dorset, for example, a body of water that within living memory was full of trout and eels and frequented by kingfishers is now an ecological desert. It is also potentially lethal for anyone seeking to bathe in its waters – E. coli has been detected there. The cause? Last year there were 2,200 hours’ worth of sewage discharges into the river – a figure which has exploded in recent years. The local water company, South West Water, says it is seeking to build a bigger storage tank at its sewage works in order to prevent such discharges.

Finally, the water industry seems to have woken up. Last week, the chair of Water UK, former Labour cabinet minister Ruth Kelly, apologised for the filthy state of rivers, describing it as a ‘chastening experience’ for the industry and promising £10 billion of investment to improve matters.

Nationwide, monitoring by Defra concluded that in 2020, only 14 per cent of over rivers (and 16 per cent of overall waters), were in good ecological condition. Water quality, it said, has remained static over the past decade. This is contrast to air pollution, which generates far more headlines thanks to Sadiq Khan’s ultra-low emission zone (Ulez) and other initiatives, but which has steadily decreased over the past half century. There are far fewer chemicals being spilled into our rivers, too. Yet on sewage discharges there has been no progress in recent years – and plenty of anecdotal evidence that things have been getting worse over a long period of time.

As with so many things nowadays, climate change makes for a convenient excuse. In its ‘storm overflows discharge plan, published in August last year, Defra asserted that sewage discharges have become more common partly thanks to ‘more frequent and heavier storms because of climate change’ which ‘have increased pressure on the system’. That is a feeble excuse: there is nothing new about heavy rainfall. Dorset, indeed, still holds the record for the highest 24 hour rainfall total ever recorded in Britain: 11 inches’ worth doused the village of Martinstown on 18 July 1955 – in the middle of a month when no rain at all fell in parts of East Anglia. You don’t have to try hard to imagine how such extremes would be reported today.

But why tinker at the edges? Why not embark now on a national programme of isolating foul drains from storm drainage?

But there is a far more fundamental reason why our rivers are awash with sewage: because in many parts of the country foul drains, which carry human waste, are combined with storm drains, which carry rain running-off from roads and buildings. This is a hangover from 19th-century sewer engineering which, while impressive in many respects, made the fateful decision to combine the two systems. As a result, when it rains heavily, sewage treatment works are quickly overwhelmed and water has to be released into rivers and the sea, untreated. There are 15,000 storm overflows in Britain where water and sewage is discharged in this way. If the discharges did not take place, the result would be worse: water would back up through the system, with the result that streets and homes would be inundated with sewage.

While storm overflows were designed only to be used in extreme circumstances, they have come to be used on an increasingly regular basis – although it is not possible to provide good data on this because it is only since the mid 2010s that comprehensive data has been collected on spill events. Last year, 3 per cent of storm overflows were used on more than 100 occasions – an average of twice a week, in other words. And that was in a dry year, when much of the country was under drought conditions. The rise in use of storm overflows is not so much because of heavier rainfall, but because the rate of run-off has increased thanks to the growth and intensification of urban development. One cause is the loss of absorbent ground in gardens. Homeowners might not think they are doing any harm by paving over their front gardens to park their cars, but they share the blame for killing off the trout and eels in nearby rivers. Overflows can also be caused by poor maintenance of sewers, with blockages causing wastewater to back up through the pipes.

There is a simple (if very expensive), solution to the problem: to separate foul drainage from storm drains, so that the quantity of material processed by sewage treatment works is unaffected by rainfall. However, under our current system of water industry regulation, water companies simply do not have sufficient incentive to invest in the necessary infrastructure.

It isn’t the case that water companies are not being caught and prosecuted for sewage discharges. In 2021, Southern Water was fined £90 million after pleading guilty to almost 7,000 illegal discharges – occasions on which sewage was released into rivers and the sea – between 2010 and 2015. The Judge handing down the sentence described it as ‘a shocking and wholesale disregard for the environment, for the precious and delicate ecosystems along the North Kent and Solent Coastline, for human health and for the fisheries and other legitimate businesses that depend on the vitality of the coast waters’. But if that was supposed to be the kick up the backside which would stimulate investment in preventing storm overflows, it doesn’t seem to have worked yet – last year, the company was recorded as having allowed a further 16,688 spill events.

The water industry has reckoned it is cheaper to pay the fines than to invest in a solution to the problem. In 2021, a study commissioned by Water UK estimated that complete re-engineering of the sewage system to keep foul drainage and storm drainage separate would cost between £350 billion and £600 billion, adding between £569 and £999 to each average annual household bill. An alternative option of retaining combined drains but eliminating storm overflows altogether – such as by building larger tanks to hold storm waters until they could be processed at a sewage works – would cost £280 billion, adding £495 to annual average bills. It also came up with lower estimates for reducing – but not eliminating – storm overflow events. Don’t be fooled by the apparent precision of the numbers: the consultants who produced the report stated that there were ‘many unknowns and uncertainties’ in the calculations, not least because there is a lack of data on the flow in some rivers.

The government does have a ‘storm overflows reduction plan’, but it is pretty glacial compared with ministers’ decarbonisation commitments: it is promising only that spill events should be reduced by 40 per cent by 2040. To achieve this, the government says, will add an extra £12 on average annual household bills by 2030, increasing to £42 a year by 2050. To reassure us that the public won’t shoulder the whole bill for the failures of water companies, the government also proposes raising the maximum fine for a spill event from the current £250,000.

But why tinker at the edges? London’s Victorian sewers were constructed over the course of a few years. Why not embark now on a national programme of isolating foul drains from storm drainage? There will a big bonus: if we take drainage water out of the sewer system we could make do with much smaller sewage treatment works, freeing up land as well as well as cleaning up the environment. Anything which continues to threaten fisheries and tourism will be a false economy in the longer term.

Should the government, in any case, simply accept a sky-high estimate for separating foul drainage from storm drainage which appeared in a report commissioned by the water industry – an industry which has proved itself, over and over again, reluctant to invest in new infrastructure, whether it be for water supply or drainage?

Water UK’s estimate for the cost of building a new foul drainage system works out at between £13,000 and £22,000 for every single UK household. You could build your own miniature sewage treatment works for less money.

At the very least, the government should seek a fully independent estimate of the cost of separating the two drainage systems. As things stand, ministers seem to believe that building a new network of foul drains will cost half as much as decarbonising the entire UK economy (which the Climate Change Committee put at £1 trillion in a 2019 report). That is ridiculous. Like Joseph Bazalgette, the engineer who gave us London’s 19th-century sewers, we should be thinking big – and this time put right his fatal error.