Environmental Engineering Reference
In-Depth Information
chemistry via pH-mediated toxicity of unionised ammonia (Alabaster & Lloyd
1980
). Algal blooms in the upper MSC will also affect the oxygenation unit
operation. First, night-time dissolved oxygen sags will become more pro-
nounced due to the increased oxygen requirements of respiration. Second,
death of the algal cells will probably cause the BOD and SOD to increase,
thereby raising the amount of oxygen required to maintain the minimum
DO level of 4mg L
1
.
The Mersey Basin Campaign via its Science Group and Healthy Waterways
Trust (HWT) is currently considering the long-term management of algal
blooms in the MSC as part of a large catchment-wide strategic study. Manage-
ment will inevitably entail a combination of both reductions in nutrient inputs
into the Irwell catchment (phosphate stripping and reductions in agricultural
inputs) as well as methods of sustaining oxygen-rich bottom waters. Longer
term improvements to WwTW effluents in terms of nutrient reductions are
anticipated through Water Framework Directive-driven initiatives.
In light of these pressures, it is apparent that some form of aeration/mixing
will be required in the upper MSC for the foreseeable future. Evidence from
earlier studies show that conditions have improved sufficiently to enable the
minimum target of 4mgO
2
L
1
to be achieved by Helixors in Basin 6 during
periods of oxygenation shutdown, when other areas of the Turning Basin
experienced depleted oxygen concentrations. There are many types of aeration
and mixing systems available, and a thorough evaluation will be required to
determine the most suitable technique based on oxygen demand and the
influence of projected algal blooms on operating efficiency and cost. The
partnership between the Manchester Ship Canal Company, United Utilities,
APEM and HWT will be essential in developing future plans within the AMP5
budget.
Conclusions
The success of Salford Quays is illustrated by the balance achieved between
encouraging a diverse and stable ecosystem whilst retaining a recreational
facility and is testimony to the holistic programme of management. The water
complies with the requirements of the EC Bathing Waters Directive; thus, the
Quays are used as a major water sports centre for the North West and success-
fully hosted the triathlon in the Commonwealth Games of 2002 and subse-
quent World Cup events. The area contains over 200 businesses and 2 000
homes. It is clear that earlier initiatives to rectify the legacy of pollution in
the MSC have also been highly successful. However there is still a long way to
go in terms of sustaining and furthering the improvements in the upper
reaches of the MSC. The success of Salford Quays shows that, with adequate
research followed by imaginative and holistic management, a sustainable
solution to poor water quality can be achieved.
