The Mayor's draft water strategy - london.gov.uk - Greater London ...

78 The Mayor’s draft water strategy
5.30 Thirty seven per cent of London’s sludge is
produced at Beckton, the largest of Thames
Water’s wastewater treatment sites, with
another 38 per cent produced at the next
two – Mogden and Crossness 82 (see Table
5.1 and Figure 5.1). Almost 50 per cent
of the digested sludge is recycled to land,
including a small amount of limed sludge
produced at Beckton and Crossness. Whilst
the use of sewage sludge on agricultural
land is considered to be the best practicable
environmental option, it can involve high
transportation costs. Over the next ten
years the company is looking to introduce
enhanced digestion at a number of its
sludge treatment centres. This will reduce
the volume of sludge as a result of solids
reduction and hence there will be less
dependence on the land-recycling outlet.
5.31 Additional capacity for the management of
sewage sludge will be needed as a result of
population growth and tighter environmental
standards. Thames Water has prepared a 25year
sludge strategy that favours processes
that (a) maximise energy recovery and (b)
minimise sludge volumes 83 . Where there is
suitable land bank availability, recycling sludge
to land remains the favoured option. To help
protect this outlet Thames Water anticipates
investing in sludge treatment to improve
product quality. However, in predominately
urban areas, the use of ‘thermal destruction
processes with energy recovery’, in other
words incineration, is thought likely to
be more appropriate, thus avoiding the
increased environmental impact and costs of
transporting the treated sludge to land.
5.32 In the longer term, the benefits of carrying
out co-digestion with other wastes, such as
municipal wastes, are attractive, particularly
from the point of view of increasing energy
production. However, the potentially negative
effects of increased traffic movements
required to transport additional material on
site, regulatory controls and the increased
operational complexity involved, would need
to be assessed on a site-by-site basis. The
London Plan states that the Mayor will work
in partnership with the boroughs and Thames
Water to ensure the timely provision of
appropriate new facilities at existing sewage
treatment works within London 84 .
5.33 The Mayor’s Municipal Waste Management
Strategy is now being reviewed. The Mayor
will work with Thames Water and with the
London Waste and Recycling Board to
identify any potential synergies between
solid waste and sewage waste management.
The Mayor will also work with Thames Water
to investigate ways in which the sludge
strategy can be developed to meet the
objectives and targets of the Climate change
mitigation and energy strategy, which he is