Environmental Engineering Reference
In-Depth Information
140000
25000
120000
20000
100000
15000
STEEL
80000
60000
10000
40000
COAL
Strike
5000
20000
Strike
Interception sewer
0
0
1970
1980
1990
Year
2000
2010
Figure 16.2.
Change in UK coal and steel production between 1975 and 2005. Arrows
indicate the steel workers' strike in 1980 and the miners' strike in 1984 (data from
DTI and ISSB).
by 84% and 34%, respectively (
Fig. 16.2
) and 70 000 jobs (25% of the total) were
lost from Sheffield's economy between 1979 and 1987. Several steel companies
closed in the Lower Don Valley and the manufacturing workforce reduced by
35 000 between 1980 and 1990 (DiGaetano & Lawless
1999
). The severe reduc-
tion in industrial activity, coupled with the installation of a new interception
sewer (1979 1993), reduced the inputs of pollutants into local rivers, particu-
larly the River Don, although contaminated sediments remained. But has water
quality also improved?
River water quality in England and Wales has traditionally been assessed
using a combination of chemical and biological measures. Biological assess-
ments have focused on benthic macroinvertebrates and the principle index
used is the Biological Monitoring Working Party (BMWP) score or its derivative,
the Average Score per Taxon (ASPT). The BMWP score ascribes a value to
macroinvertebrate families present at a site according to their assumed pollu-
tion sensitivity; sensitive taxa (e.g., stoneflies) are given a high value, insensitive
taxa (e.g., chironomid larvae) a low value. These values are then summed to give
the BMWP score for the site and the higher the score, the higher the water
quality (Hawkes
1997
). There has been a marked increase in BMWP score along
the River Don over the last 20 years indicative of an improvement in water
quality (
Fig. 16.3
), which coincides with the demise in the steel and coal
industries and improvements in the sewer system. The Environment Agency's
current classification of river quality for the River Don is 'good' to 'fairly good'
for chemical quality, but only 'fairly good' to 'poor' for biological quality
(
http://www.environment-agency.gov.uk/maps/info/river/
)
. There has been a
