Supply Chain - Wastewater Treatment - Sludge Handling & Treatment
- Burnley WwTW Catchment Strategy (2024)
- Newthorpe STW (2023)
- The Woodlands Water Recycling Centre (2024)
- Vivian (Six Bells) Mine Water Treatment Scheme (2023)
- Melton Mowbray STW (2024)
- Warrenpoint WwTW (2023)
- Beckton STW (2023)
- Macclesfield WwTW (2024)
- Cotton Valley WRC (2024)
- Perth (Bertha Park) WwTW (2024)
- Goddards Green WwTW (2023)
- Newthorpe STW (2024)
- Finham Advanced Anaerobic Digestion (2023)
- Ards North Wastewater Improvement Scheme (2023)
- Burnley WwTW Catchment Strategy (2023)
Activated sludge plant, interstage pumping station and blower building - Courtesy of United Utilities & Advance-plus[/caption]
BioMAg Magdrums - Courtesy of United Utilities & Advance-plus[/caption]
Burnley WwTW: ASP plant - Courtesy of United Utilities & Advance-plus[/caption]
Detention tank and pumping station - Courtesy of United Utilities & Advance-plus[/caption]
Sludge thickening area- Courtesy of United Utilities & Advance-plus[/caption]
Burnley STW: Chemical dosing area - Courtesy of United Utilities & Advance-plus[/caption]
Interstage pumping station and BioMag & blower buildings - Courtesy of United Utilities & Advance-plus[/caption]
Lindred Road detention tank during construction - Courtesy of United Utilities & Advance-plus[/caption]
Burnley WwTW: Odour control cover for PST4 from Corporate Engineering - Courtesy of United Utilities & Advance-plus[/caption]
Detention tank on water test - Courtesy of United Utilities & Advance-plus[/caption]
Google Maps image showing general scheme overview - Courtesy of Mott MacDonald Bentley[/caption]
Newthorpe: At Newthorpe, the secondary and tertiary treatment will be decommissioned. Only the preliminary treatment (screening and grit removal) and the primary settlement tanks will be retained as part of the new process stream.
The extension, which will be built on the field adjacent to the existing works, will use an Enhanced Bio-Phosphorus Removal (EBPR) process, in a modified University of Cape Town (UCT) configuration. This process aims to reduce chemical consumption using polyphosphate-accumulating organisms (PAO) to eliminate phosphorus.
Newthorpe STW extension Revit model - Courtesy of MMB[/caption]
Anaerobic & anoxic tank construction progress - (July 2023) - Courtesy of Mott MacDonald Bentley[/caption]
Final settlement tanks construction progress July 2023 - Courtesy of Mott MacDonald Bentley[/caption]
Build smart: Due to the depth of the final settlement tanks into the ground, flotation was the limiting factor in the design. In the preliminary calculations, the estimated slab thickness required for the tank to float in a maintenance scenario was above 1000mm. The project team, therefore, challenged themselves to try to achieve a more sustainable solution. The outcome was to install an active drainage system that, in case of maintenance, would lower the groundwater level to 2m below the final ground level. That reduced the slab thickness to 400mm, without having a major impact on the operation of the plant, as this drainage system will only be required during maintenance scenarios where the tank needs to be emptied.
Build efficiently: To carry out the earthworks for the new site, the site team has used GPS-intelligent plant that, utilising a 3D model of the ground, reduced the plant-operator interface on site, improving H&S as well as efficiency. The excavated ground has been re-used to screen the site and provide biodiversity net gain, instead of having to transport it off-site.
ASP Tank construction (July 2023) - Courtesy of Mott MacDonald Bentley[/caption]
(left) Ground modelling to explore coal seams and (right) detail of rising main welding area - Courtesy of Mott MacDonald Bentley[/caption]
Rendered 3D model of The Woodlands WRC - Courtesy of EPS Water[/caption]
View of the main MBBR treatment block - Courtesy of EPS Water[/caption]
Noggerath® inlet fine screens at The Woodlands WRC - Courtesy of EPS Water[/caption]
View of the clarifier, sludge thickener & MCC kiosk - Courtesy of EPS Water[/caption]
Chemical dosing plant at The Woodlands WRC - Courtesy of EPS Water[/caption]
Tertiary solids removal plant - Courtesy of EPS Water[/caption]
Sludge drying bed and reedbed - Courtesy of JBA Bentley[/caption]
Reedbed inlet channel - Courtesy of JBA Bentley[/caption]
Total embodied carbon footprint comparison - Courtesy of JBA Bentley[/caption]
Melton Mowbray STW before the start of works - Google Earth image[/caption]
(top left) Groundworks underway, (right) SMR UK ASP area soil stabilisation, and (bottom left) stabilised ASP area with piling and ASP base construction ongoing - Courtesy of MWH Treatment[/caption]
The net carbon reduction profile of these activities[/caption]
(left) Inlet works physical model at Hydrotec and (right) inlet works screen baffles and dye test - Courtesy of MWH Treatment[/caption]
Refurbished inlet works with three screens & bypass pipework and (inset) the inlet works prior to the upgrade with two screens - Courtesy of MWH Treatment[/caption]
Refurbished inlet works with three screens & bypass pipework and (inset) the inlet works prior to the upgrade with two screens - Courtesy of MWH Treatment
Construction work in progress (June 2021) - Courtesy of NI Water[/caption]
Construction progress (January 2022) - Courtesy of NI Water[/caption]
(left) Tertiary treatment unit being installed and (right) UV building and final settlement tanks - Courtesy of NI Water[/caption]
Sludge holding facilities under construction - Courtesy of NI Water[/caption]
The project team, and in particular the civil and MEICA contractor, worked hard to overcome supply chain issues. This involved developing a high degree of flexibility in the programme and delivery strategy to ensure that longer delivery times could be mitigated to ensure that the impact on the critical path could be minimised. NI Water also implemented measures to deal with the unprecedented levels of inflation that were being observed in the construction industry. This encouraged proactive discussion to mitigate the impact on price and programme and utilised an open-book approach to identify the real impact on projects and reimburse costs where required.
While Phase 1 was mainly constructed in areas of the site which were not in use, Phase 2 required the construction of a significant number of large structures in areas that contained the existing live treatment process, therefore careful phasing of the construction work was required. The main challenge involved the construction of the new final settlement tanks.
Two of the new final settlement tanks had to be built in a constrained area, where the redundant aeration tanks from the original works were located. Due to the depth of construction and the limited area, cofferdams were required to provide a safe excavation. During construction the existing settlement tanks, which were in close proximity to the new settlement tanks, had to be fully operational requiring careful demarcation of construction areas and NI Water operational areas.
The upgrades to the sludge handling facilities also required careful phasing as the new sludge holding tanks and sludge thickening facilities had to be constructed in the area where the existing sludge holding facilities were located. This required a detailed construction plan whereby the new facilities were constructed and brought online in stages, with new and existing facilities being used in different combinations during different stages of the process. The design had to account for the different pipework and valve configurations which would be required at each stage of the process, while ensuring that the final arrangement was as uncomplicated as possible.
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Phase 2 works nearing completion (November 2022) - Courtesy of NI Water[/caption]
As a result of the two-phase delivery, careful consideration had to be given to the electrical upgrade which was required at the site. A new motor control centre (MCC) was required for the upgraded works which would control the equipment provided in both Phases 1 and 2. The new MCC was installed during Phase 1.
Any assets from the existing MCC that had to be retained, until the Phase 2 works were complete, were transferred across. This required meticulous planning, communications and numerous shutdowns of existing plant and equipment and recommissioning to facilitate transitioning across to the new MCC.
Subsequently, Phase 2 plant and equipment had to be commissioned on the new MCC, which again required meticulous planning to complete without adversely affecting the ongoing operation of the works.
An unexpected challenge occurred during the construction of the final settlement tanks, when a bird nest was found in the cofferdam sheet piles. A specialist ecological consultant was brought to site to complete a survey and it was found that the nest was active and contained eggs. It was determined that work on the settlement tanks could continue, however, the sheet piles could not be removed until the birds had flown the nest, which did impact the delivery programme.
Warrenpoint WwTW - Courtesy of NI Water[/caption]
The objectives of the Warrenpoint upgrade met over the two-phase delivery are:
ASP4 South Tank twin wall under construction - Courtesy of Laing O’Rourke[/caption]
New inlet works under construction - Courtesy of Laing O’Rourke[/caption]
ASP4 extension and sludge improvements
ASP4 was installed under the last major upgrade at Beckton (by Laing O’Rourke), which completed in 2014 and currently treats up to 8m3/s. This project will provide two new aeration lates in separate tanks, referred to as the North and South Tank. Each are 85m long, 41m wide and 8.5m deep. Four new FSTs will be provided; each being 45m diameter and 5m deep.
A new aeration building is required to house blowers for the new aeration lanes with the aluminium clad structural steel building envelope installed by Galloway Construction Ltd. The aeration blowers are supplied by Howden, diffusers by Xylem Water Solutions and new transformers by Winder Power Group as part of a substantial upgrade to the existing electrical infrastructure for the new ASP.
The sludge improvements include new Huber Technology raw sludge screens to remove rags and improve resilience in the sludge treatment stream. Sludge treatment capacity improvements, surplus activated sludge (SAS) thickening, is by new gravity belt thickeners (GBTs), supplied by Kent Stainless Ltd in a new building. An extension to the existing sludge cake barn building to increase sludge cake storage capacity is required. The sludge steam has further resilience work by the provision of a polymer dosing facility, new electrical infrastructure, new sludge holding tanks from Stortec Engineering Ltd, and an upgrade to existing tanks.
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ASP4 North Tank completed and new blower building cladding underway - Courtesy of Laing O’Rourke[/caption]
Capital maintenance
There are a number of improvements to the existing site wide electrical infrastructure such as the refurbishment of existing LV panels. The other key element is replacing the outfall channel flap valves to prevent site flooding.
Fibre optic network upgrade
The site-wide fibre optic network will be replaced as it has reached its design limit and has no capacity to be extended to accommodate the growing operational and performance requirements. Laing O’Rourke and Atkins are working with Thames Water to develop a new network architecture based upon the utilisation of a ‘Layer 3’ backbone network. The design will incorporate four ‘Layer 2’ process networks with firewalls between each Layer 2 network and the backbone Layer 3 network. The updated network architecture will improve resilience and security of the network.
(left) 3D BIM model of new inlet works and (right) new inlet works under construction - Courtesy of Laing O’Rourke[/caption]
Another lesson learnt applied was to implement solutions with Engineered Safety in mind, both for temporary and permanent works. Engineered Safety is Laing O’Rourke’s approach, which aims to improve health and safety outcomes for those who design, construct, use, maintain and dismantle the assets (examples outlined later). This approach has helped to identify key hazards further to which simple but effective solutions have been implemented to eliminate or mitigate risks.
Notwithstanding the above implemented lessons, one of the key ethos of this project is capture and disseminate new lessons learnt during the design, construction, commissioning, and handover stages of the Beckton STW upgrade and future projects.
(left) Extract from 3D BIM model: raw sludge screens and (right) raw sludge screen civil works - Courtesy of Laing O’Rourke[/caption]
Digital build
Laing O'Rourke’s construction assurance procedure requires the use of digital build models prior to construction. Whilst the federated model aims to show the permanent works, the digital build process aims to incorporate both permanent and temporary works requirements by reconstructing the model using 2D outputs from detail design. This has allowed Laing O'Rourke to minimise health and safety risks by planning the build with better accuracy.
Drone deploy
To monitor progress in construction, drone technology has been used to capture photos and videos. Drone Deploy platform which utilises the rich data captured also allows superimposition of detail design drawings showing outline of permanent works. This tool has been used effectively in collaboration meetings to demonstrate progress or to resolve complex engineering problems, and to plan construction activities.
Point Cloud surveys
Point Cloud surveys have been used to inform the detail design. This method of survey that capture fine details of location of civil assets and MEICA plant and equipment in 3D format. Although, it requires careful treatment before incorporating into the 3D model. In particular, areas with high density of MEICA plant and equipment such as the sludge tanks, existing grit channel at the inlet works, and existing cake barn ventilation were surveyed using Point Cloud surveys.
Design challenges due to scale - constant velocity channel and grit bridges design
The scale of the works at Beckton STW created several design challenges around plant sizing, meeting performance requirements and space constraints. One example of this being the grit removal solution on the new inlet works. Conventional design methods for calculating grit channel lengths have been challenged. CFD modelling has been used to size the constant velocity grit channels and to demonstrate the proposed location of flow measurement devices are acceptable. This has reduced the length of the channel by 23m and hence the cost of civil infrastructure.
The pumps in the grit bridges are specified to remove up to 3.5kg/s and calls for an automatic system with level instrumentation to detect grit. This would make the classifiers ones of the largest in Europe. Borger Pumps and SAVECO Environmental Ltd are providing rotary lobe type pumps to achieve the specified rate. This design rate of removal is exceptionally high, taking into consideration the incoming grit from the Tideway Tunnel.
As detection systems in this scenario are not usually required in the UK, market research had to be undertaken to select the detection system in discussion with the supply chain with their experience from other industries to reach to a solution.
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(left) 3D BIM model of new inlet works screens and (right) new inlet works forebay with coarse and medium screens upstream of the constant velocity grit channels - Courtesy of Laing O’Rourke[/caption]
ASP4 North Tank under construction - Courtesy of Laing O’Rourke[/caption]
Sustainability
The project aims to minimise off-site landfill disposal by re-using spoil for engineering works or redistributing it on site through landscaping activities and creating additional biodiverse habitats. This has been the strategy included in the MMP from the inception of the project. This has been reviewed and updated with new information rising during the construction activities.
Any contaminated sections of the excavated materials were monitored with greater scrutiny, supported by chemical testing and analyses. Localised treatment has been implemented complying with environmental standards. For instance, the identification and safe method of disposal of soil contaminated with Japanese knotweed has been carefully selected with engagement from all stakeholders and planning requirements.
The above measures have assisted in ensuring construction activities are conducted in a sustainable manner.
Another area where sustainability has been considered is in concrete mix design. Due to the large volume of concrete required on site, the use of ground granulated blast furnace slag (GGBS) has been maximised in line within the parameters defined in the project specifications. This has assisted in reducing carbon footprint of the project.
Overcoming challenges - Cadent gas main diversion
An example how a complex engineering problem was solved in close collaboration with key stakeholders is the resolution of the crossing of the Cadent gas mains to enable the construction of the new inlet works channel. The new structure had to cross an intermediate pressure steel 600mm diameter gas main and a medium pressure 30” cast iron main which then split into two polyethylene (PE) mains. The mains then cross beneath the historical Victorian NOS brick barrels.
Engagement with Cadent instigated extensive and detailed assessments of the existing gas mains, this identified the need for the MP cast iron main to be replaced due to excessive ground settlement driven by changes in ground levels. The medium pressure gas main was replaced with a new 750mm steel main, which included a section inserted into a microtunnelled concrete sleeve underneath the NOS. In addition, pipe protection measures using polystyrene blocks and lightweight fill were required to minimise the loadings on the intermediate pressure mains.
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New 45m diameter FSTs under construction - Courtesy of Laing O’Rourke[/caption]
Engineered safety: (left) use of access hatch to internally access FST during precast wall installation and (right) use of RMD soldiers for aeration tank construction - Courtesy of Laing O’Rourke[/caption]
ASP4 tank walkway handrailing
The installation of walkway handrailing from Steelway Fensecure Ltd has been developed for this project and proven to reduce the site installation period and improved safety by reducing the working at height requirements. The lifting operations have benefitted from the site already having large lift capacity craneage and the construction logistics have enabled access into the working areas to align with the civil engineering works. Systemising pipework and cable containment onto the walkways for future projects are the next generation opportunities to be investigated.
Use of RMD soldiers for twin wall propping
A simple solution to negate the use of inclined props to create more workspace and reduce hazards is to use RMD soldiers. This required careful planning from the design of twin wall during temporary phase and ensuring appropriate measures are in place within the panels to allow safe fixing of the RMD soldiers in place.
Access hatch to FST walls
Another example of a simple solution to reduce safety risk is the provision of an access hatch to enable access during the erection of the precast panels, which was developed with the precast wall supplier A-Consult Ltd. This negated the need for providing high level access through temporary staircases and reduced risk of working from height.
The above examples emphasize the benefits of DfMA accrued at Beckton STW of an improved product, reduced installation period, and the on-going development opportunity that has made construction activity safer. The project has demonstrated how incremental innovation can be achieved on a relatively new and stable construction method using twin wall construction techniques.
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Precast construction of 45m diameter FST - Courtesy of Laing O’Rourke[/caption]
Use of non-piled solution
As old structures have been historically filled with mass concrete to significant depth, the reuse of these mass fill structures as foundation for new structures was explored as a safer and more sustainable solution. This enabled the project team to avoid the need for mobilising piling rigs, reduce lifting requirements and need for heavy plant and equipment. High-risk service diversions of were also avoided.
The SAS thickening system comprising the GBT building, polymer facility, potable water supply facility and the SAS storage tank all are founded on the existing mass concrete foundations. The choice of foundations was supported by structural analyses and further ground investigations.
Designer tours
To instill a culture of continuous improvement, designer tours encouraged the main designer and those from trade contractors to visit the site, inspect works being undertaken and provide feedback on how hazards are being mitigated on site. The aim being to capture feedback and consider them in future design work on Beckton STW and other projects.
New FSTs with backfilling underway - Courtesy of Laing O’Rourke[/caption]
Inlet works screens - Courtesy of United Utilities[/caption]
Drone image over the MOBTM plant cells - Courtesy of C2V+[/caption]
(left) MOBTM briquettes, (top right) fully developed biofilm on MOBTM media and (bottom right) MOBTM media - Courtesy of Nuvoda[/caption]
Mecana tertiary pile cloth filters - Courtesy of United Utilities[/caption]
MOBTM plant - Courtesy of United Utilities[/caption]
MOBTM plant - Courtesy of United Utilities[/caption]
Terminal pumping station pipework to storm tanks - Courtesy of @one Alliance[/caption]
Phosphorus removal scheme - ferrous chloride storage tanks - Courtesy of @one Alliance[/caption]
Construction of the two new storm tanks - Courtesy of @one Alliance[/caption]
Terminal pumping station pipework to storm tanks - Courtesy of @one Alliance[/caption]
Terminal pumping station pipework - Courtesy of @one Alliance[/caption]
Perth WwTW photographed from Kinnoull Hill Tower in 1971 - Courtesy of Scottish Water[/caption]
MView model showing birds-eye view of proposed design for Perth (Bertha Park) WwTW - Courtesy of ESD JV[/caption]
FST4 under construction - Courtesy of ESD[/caption]
A new distribution system will also be installed. This includes adjustable weirs and flow meters on each outlet to the FSTs. The construction will be staged, incorporating tie-ins to both existing and new pipelines, ultimately ensuring equal distribution among the four FSTs upon completion.
Google Earth image of Perth (Bertha Park) WwTW (2024) - Credit: Google Earth[/caption]
(left) Aeration lanes and (right) well-pointing to aid the construction of FST4 - Courtesy of ESD[/caption]
MView close up of existing FSTs deep tie-ins - Courtesy of ESD[/caption]
Odour model emission contours for selected solution - Google Maps[/caption]
Phase 1 odour control unit from ERG (Air Pollution Control) Ltd - Courtesy of Galliford Try[/caption]
(top & bottom left) BIM models showing the THP plant area and (bottom right) Phase 2 THP area looking north-west - Courtesy of Galliford Try[/caption]
Digester feed pumps are used to pump hydrolysed sludge from the flash tank to the digesters. Disinfected process water is added to the suction side of the digester feed pumps to dilute the hydrolysed sludge to achieve the target digester feed sludge dry solids content.
Diluted hydrolysed sludge is combined with recirculated digested sludge before being cooled while passing to the two existing digesters.
The new digested sludge dewatering stage comprises new duty/standby centrifuges and an associated polymer preparation/dosing system. Enhanced treated cake is conveyed to the new cake barn.
There is an existing 800 kW CHP engine. High grade waste heat from the CHP engine exhaust gas is recovered in a new composite steam boiler. Low grade heat is also recovered from the CHP engine jacket cooling water and used to pre-heat the boiler feed water. These heat recovery systems help to minimise the consumption of supplementary fuel (biogas or diesel) required to meet the THP steam demand.
A new final effluent (FE) pumping station supplies cooling water to the sludge coolers. All applications requiring dilution or carrier water are supplied with filtered FE that has been UV-disinfected, ensuring that an enhanced treated cake is produced.
The schematic diagram below shows the process stages with the additional odour reduction measures undertaken in Phase 1 (in green) and the main changes to the sludge treatment process for Phase 2 (in orange).
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Schematic showing the process stages - Phase 1: Additional odour reduction measures (green) and, Phase 2: The main changes to the sludge treatment process (orange)[/caption]
View looking at Serpecon conveyors and pre-THP silo feed pumps - Courtesy of Galliford Try[/caption]
THP area looking north east - Courtesy of Galliford Try[/caption]
This approach has proved successful throughout the first three years of the current programming AMP7 period (2020-2025) as it affords greater flexibility and control. Wherever possible the existing structure was retained and re-purposed to speed up the construction, and to reduce overall costs and the carbon footprint of the scheme. Before reusing the foundations, detailed in situ and pull-out testing was undertaken. The Cambi B2 unit and associated ancillary equipment are all located within the original cake drying beds.
In parallel to the cake bay works, construction was undertaken within the existing plant to facilitate the installation of the other process units. This required close collaborative working between the contractor and the onsite operations team, to minimise disruption to day-to-day activities and the running of the treatment plant. Throughout the scheme, this close cooperation has continued, ensuring all stakeholders are kept up to date with activities and progress.
Field Systems Design Ltd was engaged by Galliford Try to undertake the detailed design and installation of the complex interconnecting cabling and mechanical piping systems throughout the scheme. This included high voltage cabling and transformer upgrade works, low voltage power cables, signal cables and fibre optic networks. The scope of the mechanical supply included all piping and access arrangements, steam lines and pressure networks.
In total, 48 kilometres of cable, 2.5 kilometres of pipes and associated support systems have been installed. These systems are predominantly placed above ground for ease of future maintenance, and to mitigate the risks of burying equipment within an already congested plant. Collaborative planning and design management have been undertaken between the site team and Galliford Try, to ensure the smooth flow of the mechanical and electrical phase of the works.
Overall, the scheme is now (June 2023) approaching 200,000 hours worked without any lost time or other significant incidents.
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View looking north-east towards the Saxlund pre-THP cake silo - Courtesy of Galliford Try[/caption]
(top left) BIM model showing the steam boiler system, (top right) the rear of the steam boiler building and emissions stack, (bottom left) the front of the steam boiler building and emissions stack, and (bottom right) the Dunpy boiler package - Courtesy of Galliford Try[/caption]
Newthorpe STW: (left) site compound and storage, (top) existing site, and (bottom) the new expansion (August 2024) - Courtesy of MMB[/caption]
Heanor flows inlet works (August 2024) - Courtesy of MMB[/caption]
Enhanced Bio Phosphorus Removal UCT configuration - Courtesy of MMB[/caption]
Installation of the tertiary solids removal units (August 2024) - Courtesy of Mott MacDonald Bentley[/caption]
Heanor site overview (September 2024) - Courtesy of MMB[/caption]
Rising main site just outside Newthorpe (August 2024) - Courtesy of MMB[/caption]
Sodium hydroxide (left) and ferric sulphate (right) dosing systems
Gas to grid process diagram - Courtesy of Costain[/caption]
Thermal hydrolysis plant process diagram - Courtesy of Costain[/caption]
(left) Inflated gas holder and (right) biogas upgrade unit and carbon storage silos - Courtesy of Costain[/caption]
(left) Sludge transfer pumps and (right) elevated strain press in front of the buffer tanks - Courtesy of Costain[/caption]
Dewatering
The screened sludge is dewatered from approximately 3% to 20% dry solids for transfer to the THP feed silos. 3 (No.) centrifuges work in a duty/duty/standby arrangement and backwash with final effluent (FE) as required.
THP & boilers
The cake is diluted with FE to 16% dry solids and fed into one of the 2 (No.) THP streams which process up to a maximum of 60 tonnes of dry solids per day (tds/day) per stream.
The sludge is heated to around 95°C in pulper to become ‘homogenised’. This sludge is then pumped sequentially through each of the streams 4 (No.) reactors for batch treatment. Steam from the boilers is used to heat the sludge between 50-180°C where it is held at 6-bar pressure to undergo pasteurising hydrolysis for around 30-45 minutes. After hydrolysis, sludge is passed into the flash tank, where the pressure and temperature of the hydrolysed sludge are decreased by flashing steam back to the pulper. The flashtank provides the necessary thermal buffer capacity to release the excess energy contained in the sludge before entering the downstream pumps.
The process kills all pathogens and, in turn, increases the potential gas yield of the sludge.
2 (No.) boilers, procured from Italy, produce 192°C steam from potable water, operate at 12bar and can run on either natural gas imported from the grid or biogas produced from the gas to grid plant. 2 (No.) CHP engines are situated locally to the boilers and the exhaust gas heat is recovered by boilers to optimise performance, these CHP engines can also run on either natural or biogas. The boilers are operated by BOAS accredited operators who were transitioned across from Costain to Severn Trent upon handover.
The warm hydrolysed sludge is then blended with UV FE to reduce the temperature to around 42°C where it is fed back into the digesters via a bank of 8 (No.) sludge return pipes traversing 500m across the site footprint.
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(top left) Centrifuges, (top right) THP silos, (bottom left) the boiler and (bottom right) the boiler house - Courtesy of Costain[/caption]
UV treatment and sludge cake
A UV plant was constructed to ensure no pathogens were introduced to the sludge post-THP which would normally be present in non-UV treated FE. This ensures that the biosolids product produced by the works is ‘enhanced’ quality and can be sold to farmers to fertilise fields growing a wider range of crops than those which can have ‘standard’ biosolids. A pair of Bollfilters with 25µm strainers from Bollfilter UK Ltd screen the FE prior to UV treatment to ensure that stringent disinfection standards are achieved and to prevent particulates damage to the plant.
Other THP highlights
The THP installation also included a polymer dosing plant, FE and potable break tanks, odour control unit, deep drainage and centrate pump stations with 700m of buried return pipework to head of works, a new FE pump station and a 1200m3 cake bunker.
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THP reactors - Courtesy of Costain[/caption]
(left) Cake bunker cofferdam and (right) cake bunker - Courtesy of Costain[/caption]
CHP engines- Courtesy of Costain[/caption]
Muck shift in progress - Courtesy of Costain[/caption]
Costain worked collaboratively with Severn Trent to draft plans for the reuse of the muck in the proposed BIA and began the process of sampling and testing the muck. A comprehensive Materials Management Plan approved under the CL:AIRE regulations was produced detailing the proposal. Upon approval from all parties, the muck shift operation began. Costain operated three 30 tonne articulated dumpers (ADTs) to transport the muck across the site. Each dumper averaged 25 trips per day and the full operation was completed in just a little under two weeks.
The overall benefits were:
Finham THP & G2G - Courtesy of Costain[/caption]
Bulk excavation - Courtesy of BSG Civil Engineering Ltd[/caption]
Ards North WwTW - Inlet works overview - Courtesy of BSG Civil Engineering Ltd[/caption]
Inlet works side view - Courtesy of BSG Civil Engineering Ltd[/caption]
Screened raw sewage continues to the grit removal plant. The grit settles in a sump underneath the grit paddle. Any grit that settles in this sump is periodically aerated using the grit blower and then removed. From here the grit is transported out of the grit plant by the grit classifier and is deposited into the grit skip. From here it is removed off site for disposal.
After the wastewater has passed through the grit removal plant, flow continues to the FFT pumping station. Here influent is collected, and FFT of 48.2 l/s (summer) & 29.6 l/s (winter) is pumped to the PST flow splitting chamber.
(left) Ards North WwTW - Courtesy of NI Water, and (right) storm tanks tipping bucket installation - Courtesy of BSG Civil Engineering Ltd[/caption]
Aeration plant air manifold control valves and instrumentation - Courtesy of BSG Civil Engineering Ltd[/caption]
RAS/SAS pumping station - Courtesy of BSG Civil Engineering Ltd[/caption]
The thin sludge tank is equipped with an external mixer for the blending of the tank’s contents to feed the sludge thickening plant. A level ultrasonic with low and high-level floats are used in the control of the mixer.
Mixed sludge from the thin sludge tank is pumped to the sludge thickening plant via the two thickeners feed pumps. These pumps are progressive cavity pumps and are arranged in duty/standby configuration. The pumps are VSD controlled to allow the flow to the thickening plant to be controlled.
There are two sludge thickeners, with an individual throughput of 8.3 m3/hr @ 1.3% DS with a discharge of no more than 6%, based on a 5-hour day, 7-days per week operation at 100% of the maximum design load. The thickeners are arranged in a duty/standby configuration with two actuated isolation valves installed on the feed pipework allow this to be fully automated. If one thickener was to develop a fault, the standby thickener can resume operations without manual intervention.
Polyelectrolyte is made up on site to be added to the sludge fed to the sludge thickening plant. The addition of this chemical aids flocculation and makes thickening easier.
This plant is a liquid polymer set. The liquid poly is delivered within IBCs for the makeup process. The set mixes the poly from the IBC with water to a preset concentration rate and is then transferred to the poly storage tank. The duty poly dosing pump doses to the thickener’s sludge feed pipework from here.
Thickened sludge from the sludge thickening plant is transferred to the thick sludge tank. Here thickened sludge is stored for removal off site. A collection tanker removes the tank’s contents off site by coupling to the tank’s Bauer Coupler connector.
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PST No 1 & control building - Courtesy of BSG Civil Engineering Ltd[/caption]
The tank is equipped with a decant valve arrangement to facilitate settlement of the tank’s contents. The tank is also equipped with a level ultrasonic, low and high-level floats for level status and control of an externally fitted mixer for tank agitation.
The return liquors pumping station receives liquors from the following areas: inlet works drains, thin sludge tank decants and overflow, thick sludge tank decants and overflow, sludge thickening plant bund, FE and washwater drains and odour control plant drains. The station comprises of two fixed speed pumps, which are arranged in duty/standby arrangement. These return liquors to the activated PST splitting chamber.
Low level structures RC concrete installation - Courtesy of BSG Civil Engineering Ltd[/caption]
(left) Ballywhiskin TPS - Courtesy of NI Water, and (right) Carrowdore WwPS - Courtesy of BSG Civil Engineering Ltd[/caption]
(left) Sandycove WwPS and (right) Ballywalter Fowler Way TPS - Courtesy of NI Water[/caption]
NI Water, TetraTech, BSG Civil Engineering Ltd and Farrans along with local elected representatives to mark completion of the £18m Ards North Wastewater Improvement Scheme - Courtesy of NI Water[/caption]
ASP under construction - Courtesy of United Utilities[/caption]
Detention tank on water test - Courtesy of United Utilities[/caption]
Primary settlement tank
The new primary settlement tank (PST) civils construction is also complete, again undertaken by A-Consult Ltd using the precast concrete panel method of construction. It has also successfully passed its water test. Mechanical installation by EPS Water is now in progress on the ‘H’ frame steel structure which will support the scraper bridge. The design of the PST incorporates a fixed bridge arrangement with rotating scrapers beneath. This arrangement is necessary as the PST will eventually be covered with a GRP roof for odour mitigation. The odour control fans, ductwork and vent stack are scheduled to be installed in December.
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PST4 and ASP lane 1 on water test - Courtesy of United Utilities[/caption]
Interstage pumping station
Due to the topography and hydraulic levels across the site, a new interstage pumping station (IPS) is required to pump the effluent leaving the four PSTs up to the new activated sludge plant (ASP) distribution chamber.
Civils FRC works are being undertaken by STAM Construction Ltd and contain 94 tonnes of rebar and 900m3 of in situ poured concrete. The pumping station structure is complete and has undergone successful water testing.
The internal benching is complete and the next activities planned for the coming period will be the mechanical installation of the pumps and pipework. As the pumping station is vital to keep all flows passing through the treatment process, a standby generator will also be installed. The IPS is a two compartment design to facilitate future maintenance activities preventing the need to take it completely out of service. The new pumps have been supplied by Xylem Water Solutions who have supported the designers in providing efficient selections for the large submersible pumps and optimising the layouts of the pump chambers.
Activated sludge plant
The ASP distribution chamber is currently being constructed with all four concrete walls having now been poured. These are curing and the structure will undergo a water test in September 2023.
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ASP constructed and water tested - Courtesy of United Utilities[/caption]
In constructing the new ASP, STAM Construction Ltd have installed 650 tonnes of rebar and poured 4500m3 of concrete. The overall size of the ASP is 48m x 48m x 6.6m deep, has a capacity of 14,500m3 and comprises four lanes. Civils construction of the ASP is complete and fully water-tested with the mechanical installation of the internal pipework, aeration grids, diffusers and access platforms and walkways taking place over the next few months.
Suprafilt Ltd will be supplying and installing the internal pipework, aeration grids and diffusers. Mechanical installation of the pump stations and access steelwork etc will be undertaken by Fluid Sealing & Engineering (FSE).
BioMag®
The Evoqua Water Technologies detail design for the new BioMag® process has been finalised and the building layout confirmed. The main equipment including four Magdrums and two shear mills, process tanks, silo and pumps, which have been manufactured and are ready for delivery to site when required. The BioMag® building is currently under construction by Gallaway Construction.
The steel frame has been erected and the gantry crane and roof cladding have been installed. External wall cladding is in progress, after which attention will turn to the internal fit-out and installation of the BioMag® equipment.
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BioMag® building being erected - Courtesy of United Utilities[/caption]
Final settlement tanks (FST)
There are four existing final settlement tanks which required refurbishing to ensure adequate performance and asset life are achieved. The scope includes civils refurbishment of the tank walls which involves cutting approximately 300mm from the top of the walls before installing new reinforcement and re-casting concrete to the required coping levels.
Cutting works is being undertaken by Holemasters and FRC works self-delivered by JMS. The mechanical and electrical work is being delivered by Jacopa and comprises refurbishment of the bridge, scraper assemblies, and other ancillary equipment. Three of the four FSTs have now been refurbished with the final one due to be undertaken towards the end of the year.
Surplus activated sludge (SAS) thickening
Civils works has been ongoing in the SAS thickening process area for the last couple of months with the storage tank, drum thickener, poly plant and kiosk bases all constructed. Underground services, ducts and pipework have also been installed and tested. The filtrate return pumping station construction is in progress with the mechanical installation due to follow on.
Chemical dosing
The new ferric and caustic dosing plants comprise storage tanks, dosing rigs and dosing pipelines, all of which have been designed and well progressed in manufacture. These are being supplied by NPS Engineering Group. A new chemical delivery facility will also be provided with civils construction in this area commencing towards the end of the year and installation of the new dosing plants taking place early 2024.
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3D model of chemical dosing area - Courtesy of United Utilities[/caption]
HV works
A new, uprated HV cable has been installed from the off-site substation to the wastewater treatment works, a length of approximately 900m, passing through a number of fields and third-party land.
Motor control centres (MCCs)
To control all the new assets a number of new MCCs housed within kiosks are required around the site, along with a new site-wide SCADA system. The MCCs are all in various stages of manufacture and factory testing. The electrical installation and system integration works, including dry testing, will be undertaken in phases over a period of months as the programme for each of the new process areas dictates.
The MCCs are being built by Technical Control Systems Ltd, electrical installation will be by PICOW Engineering Group and system integration by Tata Consultancy Services.
Looking forward to commissioning
Commissioning of the new treatment process, and transitioning from the old process in a controlled staged approach, will be complex.
The existing treatment stream and process compliance cannot be put at risk or compromised and months of hard work and planning for commissioning has already taken place. Wet commissioning is due to start in April 2024, gradually increasing flows into the new treatment process over several months while the new biological process builds up and matures to a point where the improved treatment standards are being met. The forecast project in use date is October 2024.
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Aphex construction planning software map view - Courtesy of United Utilities[/caption]
Lindred Road detention tank during construction - Courtesy of United Utilities[/caption]
Work started on site in July 2022, with the first phase involving the diversion of numerous services, including gas, fibre, BT, water and power, to clear the area for the tank construction. Enabling works to provide safe access routes, segregation, and procurement of alternative car parking for the impacted business employees was also required before the main construction work could commence.
Ground was broken in August 2022 with the tank construction continuing through to December 2022 when full depth was reached. Construction of the pump sumps, inlet channel and complex benching arrangement followed.
The spring months of 2023 saw the mechanical works inside the tank take place with the installation of the pumps, pipework and access ladders and platforms. Once the internal works were complete, the roof beams were installed and the roof slabs placed on in May 2023.
The inlet and outlet pipework for the tank has now been installed, including associated manholes and chambers. To facilitate the connection of the 1200mm inlet pipe into the existing CSO chamber, a complex timber heading arrangement needed to be constructed in order to access beneath, and protect a myriad of services crossing the vicinity. All buried pipework, chambers and ducts etc have been completed and reinstatement of the area is in progress.
The civils and pipework has been undertaken by SGC Civil Engineering Ltd and the mechanical works by Fluid Sealing & Engineering (FSE).
A new motor control centre and power supply is being installed for this facility. The new control kiosk was delivered and installed in July 2023 and the electrical installation is currently ongoing with the new power supply due to be energised in October.
Testing and commissioning is scheduled to start in November, with the site achieving project in use in February 2024.
Lindred Road: Aerial view of detention tank - Courtesy of United Utilities[/caption]
Hyndburn WwTW - 3D model of storm return pumping station - Courtesy of United Utilities[/caption]
A new below-ground wet well type pumping station will be constructed with three high-flow pumps and two low-flow pumps which provides a more flexible and efficient system with greater turn down capability. A new single rising main will return the storm flows back to the head of the treatment works. A new kiosk and motor control centre will also be installed.
Planning permissions are in place and all pre-start surveys and investigations have been completed. Detailed design is nearing completion and the site has just been established. Construction is due to start in earnest in September on the new pumping station excavation. The winter months will see the civils works progress, with mechanical and electrical works due to start in spring. The project in use is forecast for July 2024.
Aphex construction planning software Gantt chart - Courtesy of United Utilities[/caption]
- The Beast at Woodhouse Mill STW
The Beast at Woodhouse Mill STWAffectionately known as ‘The Beast’, the new screen enables tankers to directly connect and pump sludge into it, rather than offloading sludge to a holding tank that is then fed into traditional screens by gravity. The technology has been used successfully in the US and will be introduced to treatment process at Woodhouse Mill. ‘The Beast’ is fully-automated and can quickly remove debris, plastics and other solids from sludge. Ed Sutherland, project sponsor at Yorkshire Water, said:“We’re always looking at innovative ways to improve the operations of our wastewater treatment works. The Beast has been tried and tested in the US and will deliver significant benefits to the operation of Woodhouse Mill. Ultimately, it enables sludge to be pumped directly into the screen, rather than the traditional method of using an upstream storage tank that feeds sludge through screens via gravity. Removing the need for an upstream feed tank will result in significant capital savings, which ultimately leads to a reduction in costs and benefits for our customers.”
"The Beast" is equipped with an integrated perforated plate VSA Drum Screen which washes, conveys, and dewaters wastewater screenings, as well as a self-cleaning screen basket and self-cleaning dewatering zone to deliver maximum efficiency. Comprising a dual motor drive powered by independent drum and auger speeds, max flow rates of up to 200 m3/h, a drum screen 5 to 6mm perforation and incline angle of 25 degrees designed to increase solids capacity, the “Beast” can also be connected through a Perrot joint to tankers or pipes. Designed without a lower drum support arm, the Beast can be used to eliminate rag accumulation. Rotating around its axis, the cylindrical filter conveys the screenings into a loading hopper placed in the centre. A set of spray nozzles washes the filter during operation. A screw placed inside the conveying pipe (with its top inside the discharge hopper), conveys the screenings towards the next treatment stage where organic substances are washed out. Subsequently, solids are compacted and dewatered in the compacting and drainage area and finally, solids are discharged through a discharge chute. The Beast will be trialled at Woodhouse Mill and, if successful, will be installed at other treatment works around the region. Saveco’s municipal wastewater sector Manager Craig Webb said:“Achieving unprecedented success in the US market, the Beast is a game changer for how we will treat sludge going forward in the UK. We are delighted to have earned Yorkshire Water’s trust and confidence to remedy the complex challenge of sludge treatment.”
For more information contact SAVECO Environmental Ltd | +44 (0)1684 299104 | https://saveco-water.co.uk
- The Beast at Pellows Waste Disposal Services
The Beast at Pellows Waste Disposal ...At Pellows Waste Disposal Services, near Truro, a typical 4.5m3 tanker (1,000 gallons) that used to take over 20 minutes to empty, can now get back out on the road to collect more liquid waste after less than three minutes discharge time. The turnaround is due to "The Beast" made by SAVECO Environmental, that with a fully integrated 5mm screen, conveyor and compactor, all in one unit, removes harmful debris and dewaters it prior to discharge. It can handle 200m3/h and up to 6-8% solids as a plug-and-play system. Payback is expected in just four months, as Pellows’ Director, James Martin, explains:“The Beast has far exceeded our expectations. It injects water to accelerate the process, and is so much more efficient and robust than our previous system. Investing in The Beast is part of a major upgrade that we’ve put into place to address the big changes that have happened in Cornwall’s collection and disposal of liquid waste.”
The upgrade at Pellows, which includes a centrifuge, aeration, and larger tanks, has enabled the company (established in 1964) to expand its customer-base by offering a complete in- house service. It will also provide a potential lifeline to other contractors who collect liquid waste from the holiday parks, factories, hotels and many thousands of homeowners in Cornwall that are not connected to the sewer network. The closure in April 2022 of what turned out to be two large disposal sites that were trading illegally, has forced contractors into sending their vehicles long distances away to discharge their collected waste. The headache has been partly alleviated by being able to take some liquids to be treated by South West Water, but during heavy rainfall and storm events, the water company has had to keep its gates closed because capacity has been reached. James Martin continued:“Storms and flooding from prolonged rainfall is all too common these days. We couldn’t just stop working for long periods due to the weather, letting our customers down, or keep sending our vehicles miles and miles away to unload. We had to act to protect and grow our business, so first contacted Centri Force, who make very good decanter centrifuges. They gave us plenty of good advice about how we could become independent by treating the collected waste ourselves, which included a strong recommendation of "The Beast" from SAVECO Environmental.”
The pneumatic press (with de-stoner) that had been in operation at Pellows not only took far longer to receive incoming waste, but, according to Richard Montanaro, Managing Director of Centri Force, was too small and far less sturdy, with too many areas where the process would require costly maintenance or be likely to slow or fail.“In comparison, "The Beast" is very well designed. It is a great product that integrates very well with other parts of a plant to provide an excellent front-end pre-screen. With a centrifuge as part of a process, it gives us exactly what we’re looking for, and has helped Pellows greatly increase productivity and take this important step to becoming a liquid waste contractor with its own treatment facility".
Environmental wet waste is a big issue, and Cornwall, with far less infrastructure and sewer connections than many counties, faces some big challenges, so it is good to see Pellows play a big part in reducing the environmental impact of septic tank liquids.” Rotating around its axis, The Beast’s cylindrical filter conveys screenings into a loading hopper placed in the centre, whilst a set of spray nozzles washes the filter during operation. A screw, placed inside the conveying pipe (with its top inside the discharge hopper), conveys the screenings towards the treatment stages, during which organic substances are washed out. Subsequently, solids are compacted and dewatered in the compacting and drainage area, before exiting through a discharge chute. Despite septic tank contents often containing solidified calcium, rocks, stones, and sanitary products, installation of The Beast now sees Pellows’ 27-tonne artics discharge waste in less than 13 minutes, compared preciously (depending on the thickness of the liquid) to 45-minutes, up to one hour. Craig Webb, SAVECO’s Municipal Sales Engineer, commented:“We have worked closely with Pellows and Centri Force to bring about a big improvement in treating liquid waste. Allowing effluent to be put directly through "The Beast", which avoids placing further stress on an existing plant, is also a huge benefit to water companies. Liquid waste contractors and the water industry can see that by screening, washing, conveying and dewatering - all in one unit - there is a reduction in risk, and the opportunity to make big savings by removing the need for multiple pieces of equipment.”
James Martin from Pellows, continued:“The whole system is so much better now. We get better biosolids too at the end of the process. Apart from South West Water, we’ve now become the first company in the County who have the capability to treat liquid waste for safe disposal into the foul sewer main.”
For more information contact SAVECO Environmental Ltd | +44 (0)1684 299104 | https://saveco-water.co.uk