Spiraling Success: New BANDGUARD Screens and SPIROWASH units Weather Storms in £43M Sewage Treatment Upgrade

At a crucial stage of a £43M upgrade, with an additional 430 liters per second (l/s) coming in from a treatment plant in a neighboring town, the last thing a contractor would want is for not one, not two, but three back-to-back storm events. Yet for one leading solution provider to the water industry, it provided the ultimate test for new inlet screens.

This important STW has been expanded from 570 l/s to 980 l/s – plus the 430 l/s, which are pumped from (pe 50,000) a nearby Shire to create a total flow of 1410 l/s.

Working to reduce steel and concrete use where possible, the client wanted to reuse the existing inlet structure; removing the need for any modifications to the existing or new civils. Using 3D digital models to increase on-site productivity, and with the benefit of SPIRAC’s vertical, space-saving screens able to reach 2m down (rather than a restrictive 1m), the inlet was meticulously planned out in the virtual space. This of course makes it so much easier and economical to fine-tune a design, rather than have equipment arrive on site, only for it to be sent away again for modifications.

Designed for 570 l/s, the old screens were not surprisingly struggling with flows up to 900 l/s, even when modified to a high-speed mode. Stormwater events sometimes saw everything having to go through the works one way or another, causing numerous blockages and thus considerable ongoing maintenance for downstream equipment.

In what is a first for our client, the new 30,000m² nature-based wetland will accommodate diluted wastewater from heavy or prolonged rainfall events, allowing pollutants and nutrients, such as phosphorus, to be broken down naturally, and taken up by bacteria and thousands of plants. By reducing the reliance on energy-heavy treatment processes, the wetland will help create wildlife diversity in the area.