United Utilities (UU) is the main regulated water and wastewater services provider for North-West England, supplying some seven million people daily. In June 2014, the company needed to undertake essential investigative work on an existing nitrifying trickling filter at Huyton Wastewater Treatment Works near Liverpool.

The work could only be achieved by taking the filter system off-line, which meant installing a temporary packaged treatment plant to keep the site operating at full capacity.

Due to a long-standing relationship with both Nomenca and WPL, UU had confidence in both company’s ability to provide a robust and reliable treatment plant within a relatively tight timeframe.

The units needed to meet a demand of 5Ml/day so that the nitrifying tertiary filter could be taken off line. WPL worked closely with the principal contractor Nomenca, to engineer design, manufacture and deliver a total of five modular transportable submerged aerated filters (SAFs) to the Huyton site.

The temporary nature of this application, and similar requirements periodically across the utility’s asset base, led to UU’s insistence that it should be possible to relocate the SAFs elsewhere within the region on completion of the project.

Redeployment request

Although five WPL ST1000 Model units were required for this project, the modular nature of the equipment means it can be readily redeployed to other sites and configured in any combination – as five units or just one.  The selected units, which come complete with skid-mounted kiosks and manufactured in steel, are designed to be robust enough to withstand the rigours of transportation. Each unit is container-size and fits on the back of a lorry.

Andrew Haywood, Utility and Industrial Sales Manager states "In discussion with United Utilities and Nomenca a  temporary solution was offered for Huyton. A side stream treatment plant was required whilst  investigative work was undertaken of an existing asset which needed to be taken off line. A range of temporary, above ground, portable, off–site build tertiary "submerged aerated filters” were proposed. Using the clients specified loading rates, 5 modules were proposed, each designed to treat 1 Ml per day.”

Modular Design – keeping whole life costs low

The modular packaged treatment plants, including the blower panels, are built off-site at the WPL factory prior to transportation to ensure quality control and keep whole life costs low. This means fewer workers are required on-site, which minimises health and safety concerns, and installation can be completed in one day.

Flow challenge

The 5 modular SAF tanks were arranged in parallel due to the restricted footprint, but equal flow control still had to be mounted to each SAFWPL advised Nomenca on each SAF tank limitation based on UU specification.  This allowed Nomenca to design a 5 way flow splitter using a novel submerged orifice to restrict flow to the tanks.

Time challenge

Timings were a major challenge for the project as the blowers were on a particularly long lead-time. However, by working closely with suppliers the project was delivered on time and to budget within a limited time frame.

Limited Footprint

The due diligence for delivering, offloading and positioning the 5 modular SAF tanks on site, was WPL’s responsibility. All tanks were off-loaded on the limited footprint, installed and set to work under automatic control within the agreed contract times, much to the satisfaction of the client.

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