How clean is our stream?

Today we tested the water quality in the stream in Coldfall Wood.

The results were mixed but not great!

Using portable Hanna checkers we tested for ammonia and phosphates upstream by the reedbed notice board and downstream in the ‘everglades’ area before the boardwalk bridge.

According to the UK’s Water Framework Directive Classifications, the level of ammoniacal nitrogen was moderate upstream (1.52mg/l) and very good (0.55mg/l) downstream.

The level of phosphate came out as bad in both locations – which is the worst level under the WFD Classifications. Upstream was 1.31mg/l and downstream was 1.35mg/l.

Ammonia would suggest sewage is entering the stream. Vegetation in the stream can help to filter it and it was diluted by the time it got to the downstream site. Phosphate could also be from sewage, road run-off and from washing machines, car washes or other detergents.

In London we have two waste water systems, one takes sewage and foul water and goes to a sewage treatment plant and the other takes surface water, ie rain from our gutters and goes untreated into local waterways. If someone plumbs a toilet or washing machine incorrectly into the surface water drain, it will end up in the local stream. So sadly, some misconnected plumbing locally is polluting our stream.

The water companies can detect misconnections and require the homeowner to put them right but they are nowhere near to tackling the scale of the problem.