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Phosphates originate from many sources, including sewage and manure, and are also found in many artificial fertilisers. In a similar way to nitrate – excess phosphate in watercourses causes a nutrient boost which often results in excessive algae growth. The algae may then produce toxins that adversely affect the aquatic ecosystem, reducing oxygen levels, impacting fish stocks and leading to loss of species and degradation of the waterway.
In early October 2022 Adam and I used some testing kits to check the levels of Phosphates and Nitrates coming from the Sewage outflow pipe into the Teifi from the outflow pipe below Cilgerran Castle at the confluence with the Plysgog.
Here are the results we obtained: For Nitrates
and for Phosphates:
Is there a safe level for nitrates and phosphates in a water course? I can see that in both your images there is the highest levels of both in the Plysog/Teifi which is presumably bad but what would be an acceptable level?
Bear in mind that we tested the water coming out of the sewage pipe, not the river water. There is a lot of info available, and can be quite confusing:
This is a NRW report – https://naturalresourceswales.gov.uk/about-us/news/news/tighter-phosphate-targets-change-our-view-of-the-state-of-welsh-rivers/?lang=en
UK Government guidance recommends that rivers should not exceed annual mean phosphate concentrations of 0.1mg per litre. https://view.officeapps.live.com/op/view.aspx?src=https%3A%2F%2Fassets.publishing.service.gov.uk%2Fgovernment%2Fuploads%2Fsystem%2Fuploads%2Fattachment_data%2Ffile%2F1126652%2FPhosphorus-challenges-for-the-water-environment.odt&wdOrigin=BROWSELINK
The UK drinking water standard requires the nitrate concentration to be less than 50 parts per million. https://thewaterprofessor.com/blogs/articles/nitrate-in-drinking-water#:~:text=The%20UK%20drinking%20water%20standard%20requires%20the%20nitrate,common%20problem%20for%20private%20water%20supplies%20%28water%20wells%29. NRW has much ino too: https://naturalresources.wales/about-us/what-we-do/water/nitrate-vulnerable-zones/?lang=en
In the US recommendations officially state the limit for nitrates at 10 mg/L. Nitrates in Water? Safe Levels and How to Remove it – Pick: Comfort
Hope that helps
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