According to Earthwatch which runs the Thames Water Blitz coming up again this weekend, phosphate levels between 0.05 milligrammes per litre and 0.10 mg/l indicate moderate pollution and over 0.10 mg/l indicates high levels of pollution.
Below Naunton STW on 17 April.. 0.13 mg/l. It was 0.07 just above the works about the same time. We are building up our database and sharing our data.
Sewage works discharge phosphate in treated effluent and untreated sewage releases, and the volume and concentration set against the size of the receiving river will dictate the dilution and level of phosphate in the receiving watercourse.
If the sewage works treats less than a population equivalent (numbers of residents + other alowances like trade effluent) of less than 10,000 they are not required to remove phosphate unless the works dicharges to a site of special scientific intrerest or similar protected environment.
That requirement can be over ridden but removing phosphate costs the water industry money and it seems that the cost benefit calculations made by the industry and Environment Agency almost always put money before the health of the nation's rivers. That is a recurring theme.
Th problem for little rivers like the Windrush, is that they are so small that the sewage works have a disproportionate effect. The works are big enough to harm small rivers but not big enough to fit the one size fits all 10,000 population trigger point when things can be made better.
Quite a happy river rolling in to Naunton. Already had its first dose of effluent at Guiting Power, though.
At Naunton, the sewage works is serving a small village. We know they had problems with ground water or springs getting into the sewer and we know from local people that the pumping station had problems. Thames Water have told us they have lined a lot of sewer pipes and solved the problem of the infiltration. This has to be an improvement and good news.
However, they do not remove phosphate at the Naunton sewage works and the standards of effluent required by the Environment Agency are, according to Thames Staff we have spoken to, not very challenging. This is also a recurring theme that we hear. - '' The Environment Agency doesn't ask us to do any better so we can't do any more than we do '.
It is disappointing and worrying when the agency we think is protecting our rivers is being given as a reason to pollute them. There is more on that to come and we know that the EA staff we speak to definitely don't want to accept pollution as normal business. But that is what is happening to many rivers, every minute of every day..
That's filamentous algae below the sewage works. I don't know why I'm smiling..
The nature of the river below the Naunton works certainly looks inferior to that above. There is little weed and large clumps of filamentous algae appear instead. The sensitive ranunculus is pretty much gone until the river reaches a massive influx of clean spring water with a phosphate level so low, it does not register on our tester. More on that next time. It is spectacular.
This is the Windrush below Naunton. We know the invertebrate life is good but the aquatic plant life is certainly not.
We don't know why this is yet but we are starting to see some trends and potential causes as you can work out..
It is also true that the water industry is not the only polluter and most of its pollution is legalised, but that does not make it right and it does not mean that it should continue in this way. If we want clean rivers back, it has to change.
Our environment does not care if pollution is legal or illegal. Things just die.