Since 1987 APEM has monitored and managed the water quality and ecology at Salford Quays in Manchester, implementing innovative projects to reach and maintain the highest possible levels of environmental quality.
This is now one of the longest running and most successful urban environmental improvement programmes of its kind in the world.
Salford Quays were once part of the thriving Manchester Docks at the head of the Manchester Ship Canal. For most of its life the canal provided vital access to world trade routes and helped establish Manchester as a major international commercial centre.
However, by the early 1980s containerisation and changing world trade patterns led to the demise of the docks, which were closed to commercial traffic, leading to severe urban decline in the area.
The combination of water frontage and its location near urban centres made the land at Salford Quays highly attractive in terms of redevelopment.
However, poor water quality precluded such development due to aesthetically unpleasant floating rafts of sediment, bubbling of hydrogen sulphide and associated unpleasant odours.
Initiatives to improve conditions began in the 1980s as part of an overall development plan supported financially by the government.
Salford City Council bought much of the land surrounding Salford Quays. Three of the Salford Quays basins were then isolated from the Ship Canal during 1987-89 in order to prevent pollution from entering them from the Ship Canal. The aim was to create a focal point for redevelopment by improving water quality in the Quays.
APEM has played an instrumental role in this development since the mid-1980s.
Although the water in the Quays was cleansed of organic pollutants within weeks of being isolated from the Ship Canal, stagnation caused by thermal stratification remained a significant problem.
Thermal stratification, or layering of the waterbody, is a common occurrence in similarly shaped waterbodies, such as docks, reservoirs and canals, and is exacerbated by the quayside vertical walls and deep nature of the basins (up to 7 m).
This can result in significant oxygen depletion of bottom waters from the biological activity of the microscopic plankton in the water column itself, and from the oxygen demand of the sediment, leading to unsightly bubbling and anaerobic conditions.
Some form of artificial mixing (aeration) was therefore required to overcome this stratification and improve the water quality of the basins.
As part of the overall water quality management strategy a number of artificial aeration systems (Helixors) were therefore installed into the Quays between 1987 and 1988. Six Helixors were also installed in South Bay, which is still connected to the MSC.
By completely turning over the water in the Quays Basins (typically taking around 4-6 hours to achieve) water column oxygen levels could be replenished from the atmosphere.
Helixors use compressed air to aerate the water column. Compressed air is supplied to the base of the unit (which is open) to allow water to also be drawn in at the base. An internal helix component inside the tube causes this to form a highly turbulent flow of air and water as it rises through the device, drawing water in at the base and discharging it at the top.
This generates circulation from surface to bottom within the waterbody, leading to increased atmospheric re-aeration of the water column.
The Helixor mixing system has proven very effective at maintaining a well-mixed water column. The figure below clearly indicates how the oxygen differential recorded in 1986 was overcome by the installation and effective operation of the aeration system (see the 1989 profile). The most recent summer profiles indicate a well-mixed water column.
The physical homogeneity within the Quays also posed a major limitation to the overall ecological stability of the system. This originated from its industrial past, with deep basins, vertical walls and featureless sediment.
As a remedial action a programme of habitat diversification was devised with the aim of creating a more complex food web, promoting colonisation, and providing refuges and spawning substrate for fish.
To date, artificial reefs, floating islands, spawning habitats and lily stands have been introduced into the Quays to improve the diversity of the habitat. These efforts to increase heterogeneity were necessary at a time when natural colonisation by macrophytes was not considered a possibility, principally due to the basin depths.
In recent years, however, water clarity within the Quays has increased to a degree that has facilitated the development of macrophyte stands.
Despite the now extensive and plentiful habitats provided by the submerged macrophyte stands, maintaining the floating islands in good condition is considered important as bird nesting platforms, as well as from an aesthetic perspective.
Plant management activities therefore continue to be essential in the Quays to avoid competition and excessive plant growth from the more prolific species, and to help develop a more diverse plant community. Maintenance work is undertaken on the islands each year to strengthen and improve the structures.
With the improved water quality and invertebrate community APEM stocked the Quays with 12,000 coarse fish in 1989, following a trial in the preceding year. There is now a thriving fishery present. Indeed the Quays supported one of the fastest growing fish populations in the UK.
The significance of this achievement was recognised by the Institute of Fisheries Management and the Angling Foundation, which awarded Salford Quays the UK’s most prestigious fisheries award, The Good Management Award.
Algal blooms became problematic in the enclosed basins during the early 1990s, as light began to penetrate the nutrient-rich waters due to a reduction in suspended solids previously received from the Ship Canal. The blue-green species Oscillatoria sp. dominated, increasing with both frequency and intensity in the four years following isolation to a peak in the summer of 1992.
Throughout the five years thereafter, the algal biomass remained high but showed a gradually decreasing trend towards 1998, after which a stable and low algal biomass was achieved.
In the absence of nutrient additions to the enclosed waters, it was suggested that internal recycling of nutrients initially played an important part in sustaining the algal blooms. Over the longer term, nutrients gradually became locked within the oxygenated sediments due to operation of the Helixors and were therefore unavailable for use in algal growth, ultimately resulting in the observed biomass reduction.
Over the project duration APEM has also trialled a number of algal management solutions, including Ultrasonic, chemical dosing, light limiting dyes, barley straw and surged aeration.
On-going monitoring programme
APEM carries out routine and ad hoc monitoring, sampling and reporting at the Quays in order to maintain their water quality and ecology and to inform their use as a recreational waterbody.
Surveys are undertaken on a weekly and monthly basis to provide information to ensure efficient operation of the Helixor system and to ensure potentially detrimental impacts are minimised. This consists of sampling for a range of water quality parameters as well as biological parameters including zooplankton, phytoplankton, fish, macroinvertebrates and bacteriology.
Perhaps the most important feature governing ecological stability within the Inner Basins is the provision of sufficient dissolved oxygen. APEM therefore manages the Helixor system within Salford Quays to maintain a minimum bottom water saturation of 80 per cent, as well as a well-mixed water column. The Helixors are considered fundamental to the maintenance of a balanced ecosystem within the Quays.
In case of system failure and to maintain adequate oxygen concentrations, APEM has agreed with the Environment Agency that hydrogen peroxide dosing can be undertaken to raise oxygen concentrations.
APEM’s monitoring for recreational purposes includes blue-green algae and bacteriology, which are assessed for compliance with the World Health Organisation guidelines and EC Bathing Water Directive.
The Quays have been transformed since isolation into their current condition with Blue Flag water quality status and 100 per cent compliance with the mandatory standards of the Bathing Waters Directive in 2015.
This has enabled them to host a number of major swimming events including the Commonwealth Games triathlon swimming stage in 2002 and the Great Salford Swim in 2010 and 2011. Regular open water swim events are also held between May and October.
APEM also collects and disposes of aquatic litter within the Turning Basin of the MSC so that Welland Lock can be operated without litter entering the Quays, as well as from within the Quays basins themselves when required.
APEM provides expert advice on any aspect of water quality and ecology in the Quays to a range of stakeholders, including Salford council, the water sports centre, residents and Peel Holdings (which owns and operates Dock Nine).
In recent years this has included presenting to residents on the requirement for Helixors to operate within the Quays, liaising with residents regarding a noise issue with the South Bay compressor, and attending meetings to provide advice to Salford City Council and stakeholders on the management of blue-green algae.
Managing water quality at Salford Quays
- Development of a water quality management strategy
- Almost 30 years of continuous water quality and ecological monitoring
- Management of the aeration system
- Habitat diversification
- Fish stocking
- Algal bloom management
- Monitoring blue-green algae and bacteriology for recreational use
- Zooplankton, macroinvertebrate and algal sampling and analysis
- Hydrogen peroxide dosing
- APEM’s work with Salford City Council transformed the Quays from a barren and redundant port into a thriving water recreation centre. Water quality improved and the invertebrate community developed from a limited pollution-tolerant fauna into a diverse community with many clean water species. A thriving fishery then followed.
- The Quays are now an oasis within an urban setting. The area incorporates modern apartment buildings, office developments, retail outlets, bars, restaurants, the Lowry arts centre and Media City UK, which includes major facilities for the BBC and ITV. The shift from deprivation and decline in the Quays area to its current prosperity is inextricably linked to the history of water quality within the Quays and Manchester Ship Canal.
- APEM continues to be responsible for the monitoring and management of the water quality and ecology in Salford Quays in what is now our longest running project.