Thames Water Bromate Treatment

From NRVRA

Blue path is for bromate pre treatment works construction traffic. This crosses the New River onto a temporary road.
Red path is for bromate pre treatment works chemical deliveries - this is through NRV.
Green path is the current route used for chemical deliveries
Pre treatment building will be on the far corner of the water works near the tunnel under the railway.

History

• A bromate treatment works is needed at Hornsey is because of industrial contamination upstream.
• This contamination came from a factory near St Albans which was closed in the 1980's and now has a housing development built on the site. Thames Water would like to contain the contamination at the source but it is legally complicated.
• The bromate levels need to be kept below 10 microgram/litre. Bromate is a known carcinogen (cancer causing).
• Hornsey waterworks is the first point where it was realistic to site the bromate treatment works as there is already a waterworks at the site.

The New River has two sources of water - springs and the River Lea. The springs have the bromate contamination. The solution at the moment is to increase the proportion of water coming from the River Lea as opposed to the springs. However in Summer the River Lea can have algae blooms which clog up the waterworks filter beds. The pre-treatment works being built will allow more water to be taken from the River Lea instead of from ground water (which is the temporary solution). The treatment method to remove the algae is flocculation.

Works to actually remove the bromate may be added at a later date - this will need a new planning application. This will probably be done by filtration.

This situation is rare and has only been found in one other case in California, USA.

Planning

There was also a recent planning application HGY/2008/1262 to change condition 6 of planning application HGY/2006/1298 - for the building of the Thames Water bromate pre-treatment works. This is so they can work an extra 2 hours every day and even more hours on Saturdays. Unfortunately this application has been approved:

During the hours 1800 - 1930 Monday to Friday and 1200 - 1800 Saturday only internal (housed) works shall be permitted, with no truck deliveries permitted during this time. The applicant shall implement a temporary off-site car park for workers, with associated mini-bus transportation.

Links

• Planning Application HGY/2006/1298 (June 2006)
• Bromate information on Wikipedia