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Abstract
Bournemouth Pier bathing beach has failed to comply with the "Guideline"
standards, set in the Bathing Water Directive, in 10 out of the last 12
years, despite significant investment in reducing point source inputs.
The main reason for this non-compliance is the Bourne Stream, which
discharges close to the bathing water.
The
aim of this study was to investigate whether two constructed wetlands on
the stream were significantly improving the water quality of the stream.
The first of the two wetlands, the on-line system was installed in March
2000. The second off-line system was installed in March 2001. The
objectives of this study were to analyse general water quality data of
the stream from 2001, 2002 and 2003, and to assess whether the wetlands
were reducing highway run-off in the stream. The general water quality
data included pH, dissolved oxygen, biochemical oxygen demand (BOD),
E.coli, Total coliforms, nitrates and temperature. To assess if
the wetlands were reducing highway run-off, samples were analysed using
gas chromatography and samples of total dissolved solids were also
taken.
The
general water quality data from 2001 only showed significant effects on
dissolved oxygen levels in the stream. The data from 2002 showed that
the constructed wetlands made a significant difference to pH, dissolved
oxygen and nitrate levels. The 2003 data only showed significant
differences in dissolved oxygen, BOD and total coliforms.
Results
from the gas chromatography data for hydrocarbons (2003) showed
reductions in total naphthalene and n-alkanes of 75%. Samples taken from
the off-line wetland showed a 50% reduction in hydrocarbons after 24
hours retention.
In
conclusion the wetlands are making some improvements to the water
quality of the stream. However studies undertaken by the Urban Pollution
Research Centre and the Water Research Council into the use of
constructed wetlands show much greater improvements in water quality.
Contact
the author:
garybroocks@yahoo.com
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