River Lea water quality results – October

Phosphate-fed Duckweed on the River Lea near Bow Locks

The table below shows the water quality test results for October 2012. The samples are tested at a lab in the University College London (Department of Civil, Environmental and Geomatic Engineering).

Faecal Bacteria

As a comparison we’re using the European Union Bathing Water Directive which sets a limit of 2,000 colonies of e-coli in 100ml of water. From the table you can see that almost all of the sites breach this limit over the last month. The highest levels are just south of where the outfall from Deephams Sewage Treatment Works enters the Lea, at site 8, and another increase between sites 5, 6 and 7 where sewage from homes in Hackney and Haringey are sending wastewater down the wrong pipe into the river. A third of homes in some areas have connected their waste to pipes meant only for rainwater.

                                       e-coli –  N0. of faecal bacteria colonies per   100ml of river water

Site No. 25.9.12 04.10.12 15.10.12          29.10.12
1 Bow Locks TNTC 500 200 600
2 White Post Lane Site Closed 0 200 200
3 Leabank Sq TNTC 1,400 TNTC 300
4 Lee Conservancy Road 0 900 0 300
5 Riverside Close TNTC 5,000 4,000 6,000
6 Watermint Quay TNTC 13,000 7,000 36,000
7 Reedham Close 0 40,000 0 20,000
8 Pymmes Brook 10,000 10,000 30,000 10,000
9 N. of Tottenham Lock 2,000 0 0 1,000

TNTC = too numerous to count


As a result of all of this effluent entering the Lea, phosphate levels are excessively high. The Environment Agency says anything above 0.1 milligrammes of phosphate in 1 litre of water is high. The Lea from sites 1 – 8 never falls below 1.7 mg of phosphate per litre for the tests carried out on the 29th October. This is seventeen times the Environment Agency’s high rating. The highest result is 2.7mg/l at site 5. Phosphate is a fertiliser so it makes plants grow more quickly. On the Lea, this sees the ecology of the river knocked out of balance, with Floating Pennywort and Duckweed cutting out sunlight and using up too much oxygen.

A map of where the water samples are taken from is here 

For more information, please contact Theo Thomas/ 07968 012 828