Magic on the Mersey Valley

A United Utilities project to upgrade a wastewater pipeline and pumping station has improved efficency – and reduced operational costs, too.

In today’s competitive business landscape, doing “more for less” is the name of the game for many businesses, and competition is fierce in all sectors of the energy industry. Companies need to see how and where they can address costs and increase daily operational efficiencies.

Seeking a way to reduce operational expenditure and increase operational efficiencies lay at the heart of a major United Utilities (UU) project to upgrade a 40km wastewater biosolids pipeline and pumping station network serving large areas of the North-west. UU looked to expert assistance through its framework partner, Siemens, to help improve the control and management of the volumes of waste being transported through its pipe network to a central processing centre – as well as underpin a business need to augment capacity so it could safely and effectively transport and treat expected increasing raw waste volumes in the future.

Collaboration with Siemens Industry Automation has seen the implementation of a new automated PCS7 distributed control system (DCS) across the length of the pipeline – a system that is now delivering a range of benefits for UU. The provision of DCS to monitor the whole catchment, along with some plant and process improvements will achieve a 40-50% reduction in operational expenditure per cubic metre of raw waste treated – at the same time as increasing its processing capacity.

This single process control platform provides accurate real-time pipeline performance data analysis and reporting, reduced unplanned maintenance occurrences, enhanced self-diagnostics, improved visibility of the pipeline network, and forms the foundation for further planned process enhancements to the daily operation of handling and treating biosolids from a regional population of 3.5M people.

Expenditure levels

At the centre of the upgrade is the Mersey Valley Sludge Pipeline (MVSP), a 40km pipeline network that handles raw waste across the North-west.

The sewage pipeline feeds into the central Mersey Valley Processing Centre (MVPC) at Shell Green in Warrington and it was a need to better understand and manage the control and treatment of the waste to the centre that underpinned UU’s desire to seek a new process control solution. By doing this the company believed it could address overall operational expenditure levels.

The Shell Green processing centre handles up to 87,000 tonnes of biosolids waste annually with the treated waste either ending as material for export for agricultural purposes or incineration to produce a sludge cake substance for use in landfill. With the processing centre receiving incoming waste from several separate feeder sites along the length of the pipeline, the quality (% dry solids) and age of the biosolids being transported and treated was of primary concern, as it has a considerable effect on the cost to pump and treat. UU management at the central processing centre required a better prior understanding of the consistency of the raw material it was about to receive so it could improve the management of the sources of the biosolids waste.

Homogenous consistency of the feed stock or raw materials sent to the processing centre is important as it directly influences the efficiency of the operations at Shell Green. If raw materials are either too compact or too watery, it means the treatment process of the waste can lead to significant additional expenditure.

In the incineration process, if the material is too wet when entering the process it will need additional energy resources to reach its optimum auto-thermic state. In such cases, UU is exposed to extra operational expenditure through higher gas consumption.

Greater control

The solution provided by Siemens to help bring the processing centre under greater control involved the generation of a PCS7 distributed control system for the pipeline and pumping station network. This provides a single and consistent DCS platform across the length of the pipeline linked to the processing centre so that through control, monitoring and accurate reporting greater efficiencies could be achieved. The new control platform now allows the centralised operational staff to identify the consistency of the raw materials at a much earlier stage along the pipeline and then use real time data and analysis to decide the optimum way to treat it.

The DCS system, through this early material identification, provides management with remote visibility of the performance of each of the distributed donor sites that feed into the pipeline. With closer control, more accurate decision-making can be taken concerning the materials being sent along the pipeline before it reaches the MVPC.

It provides the information to get it right first time. Two other critical features of the DCS system have also supported UU in its objective to improve its OPEX commitments. Firstly, the implementation of a DSL wide area network with VPN technology as part of the solution so that improved connectivity is built into the DCS platform – as opposed to the previous reliance upon leased lines – has provided benefit. This ensures the operational management has accurate and timely information at their disposal.

Likewise, access via Profibus technology to the performance of the remote sites has vastly improved the ability for self diagnostics and had a real impact on what has been costly maintenance commitments.

Traditional high maintenance spend is being turned on its head as a programme of predictive maintenance has been put in place courtesy of the visible diagnostic sequence steps available via the DCS platform. UU expects 80% of its maintenance commitments across the pipeline to switch to a planned/proactive nature by 2012, as opposed to just 10% in 2009. Planned or predictive maintenance brings with it cost savings, improved critical equipment reliability and better overall plant availability as previously undetected issues are dealt with on a proactive basis before they can interfere with day-to-day performance.

The DCS platform is now delivering real and quantifiable benefits for UU. At the start there were several challenges to this project, including the need to reduce OPEX at the processing centre; trusting a new and different technology as the DCS solution is vastly different to the traditional SCADA platform; the ability to integrate the various elements of the control platform without affecting the day-to-day operation of the pipeline and processing centre, and the proposed use of VPN technology as a reliable source of data transfer especially for reporting needs.

The challenges have been met and the DCS solution supports the central objectives set for the project, which was to improve OPEX performance, while seeking to improve the overall ability to handle increased volumes of raw waste over the short and long term.

As a result of the pipeline upgrade UU has redesigned its processes which have directly led to measurable reductions in its overall energy use as well as levels of chemical procurement needed as part of the treatment process at the centre in Warrington.

It now boasts a more reliable hardware solution that will provide 15-25 years of fully supported performance capability. It has also given UU a foundation for extra project enhancements that will allow it to continue to service the needs of the many millions of people the Mersey Valley Pipeline and Processing serves.

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