Product category:
Hydrometry, Environment and Floods
News Release from: Black and Veatch | Subject: Broken Scar
Edited by the Processingtalk Editorial
Team on 12 July 2004
Water purification from River Tees
extraction
Black and Veatch explain their Broken Scar water treatment project for Northumbrian Water, a new GAC plant to remove natural organics, providing 180 MLD, from raw water extracted from the River Tees
Black and Veatch explain their Broken Scar water treatment project for Northumbrian Water, a new GAC plant providing 180 MLD, from raw water extracted from the River Tees Broken Scar in Darlington is one of the principal Northumbrian Water water treatment works, serving the population of Darlington, Stockton and parts of Middlesbrough
This article was originally published on Processingtalk on 31 Aug 2004 at 8.00am (UK)
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A professional services contract was awarded to Black and Veatch Limited in February 2001, as a subcontractor to the main contractor M J Gleeson, to produce an Agreed Target Cost (ATC) for a new GAC plant and relift pumping station as the new process stage at Broken Scar.
The objective was to design the GAC plant to achieve a maximum level of THM in the treated water of 30 microgrammes/litre.
A Conceptual Design Report by Binnie Black and Veatch formed the basis of the design, which comprised a bank of seven filters with associated airscour and backwash services, GAC loading and removal facilities and dirty washwater transfer pumping to the raw water reservoir.
A remote relift pumping station transfers the filtered water from the existing rapid gravity filters to the new GAC adsorbers, from where the treated water gravitates back to the existing chlorine contact tank.
The team charged with arriving at this ATC included representatives of the client, Northumbrian Water, the process contractor, Black and Veatch, the civil contractor, M J Gleeson, the civil designer, Binnie Black and Veatch, and the cost consultant, Faithful and Gould.
Extensive value engineering studies took place, taking into account various process and operational considerations, together with civil constraints such as the difficult soil conditions and hydraulics across the site.
A HAZOP study was also carried out and eventually the GBP10m project was awarded in July 2001.
The footprint of the GAC block measures 80 metres by 30 metres, in which is contained the seven GAC adsorbers, machinery room, inlet and GAC loading/removal gallery, outlet gallery, and MCC room.
The adsorbers are duplex Paterson Candy KB plenum-type floors, arranged in one parallel row.
Each adsorber has an area of 108 square metres and operates at a nominal design rate of 10 m/hour.
Backwash water is supplied from a washwater holding tank, using two submersible-type pumps in a dry-arrangement, operating as duty and standby.
Airscour is provided from a single blower.
Dirty backwash water is returned from the holding tank to the raw water reservoir, using duty/standby pumps.
GAC loading and removal is carried out automatically, using a pipework arrangement connecting from the tanker parking area feeding into each adsorber.
Motive water is provided using a single dry-arrangement submersible pump.
The adsorbers are designed to ensure a minimum 96% removal of GAC.
A new chlorine dosing point of application is being provided in the mixing chamber in the GAC return pipe to the existing chlorine contact tank.
The existing chlorine dosing point of application is being retained to allow maintenance of the new GAC facility should this be required.
A 12 metre diameter shaft forms the sump for the relift pumps, containing three vertical lift variable speed turbine pumps, supplied by Flowserve Limited.
The pumps operate as duty, duty assist, and standby and are controlled by plant demand.
Feed to the new GAC adsorbers is through a 1400 mm diameter cement-lined ductile iron pipe.
A dynamic model of the whole system was carried out by Binnie Black and Veatch, to take into account the implications of pump operation across the operational range and surges in the event of pump failure and power failure.
It also investigated the effect of the new operating regime on the existing works under all operational conditions, and actions were taken to ensure process safety.
Throughout the project, Black and Veatch have made extensive use of their 3-D modelling capabilities.
Not only does this provide a dynamic model of what is being designed, detailed general arrangement and isometric drawings are produced.
This ensures that there are no clashes of services within the design and fabrication of pipework can be carried out directly from the isometrics.
This capability was particularly useful prior to award of ATC.
It provided Northumbrian Water operations and maintenance personnel with a 'picture' of the final works, and assisted greatly in the value engineering and HAZOP studies.
Programme Installation of pipework and equipment commenced in April 2002, and was carried out by Black and Veatch contractor ABC Stainless Limited.
Electrical work began in June 2002, and Black and Veatch appointed Intelect Limited as the electrical contractor.
Mechanical and electrical installation in the GAC adsorber block was completed by the end of July 2002, followed by installation of the relift pumps in August.
The Black and Veatch control system contractor Aston Dane Limited had the software complete by July 2002, with a view to system testing in August 2002.
Pre-commissioning will began in September 2002, with loading of the GAC in November 2002.
The new GAC plant was fully operational by March 2003.
Note: The author of this article, Eur Eng Bob Rose BSc, M I Chem E, C Eng, is Project Manager with Black and Veatch Limited, Isleworth, Middlesex.
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