While newer technologies, such as ARMStorm for combined sewer overflows and ARMPhos for phosphorus treatment, have seen great success in treating wastewater, passive reed beds remain the most popular natural solution when there is no power on site - as seen with our project at Lower Basildon Wastewater Treatment Works.
Lower Basildon Waste Water Treatment Works (WwTW), operated by Thames Water, is located within Beale Park, seven miles northwest of Reading. Serving a population equivalent of 166 (as of 2011), the system uses gravity to collect sewage and direct it to a coarse screen in a small chamber. The screened sewage then flows to six buried soak-away units, which often flood during high load periods. Historically, the site had no discharge consent. However, in 2011, the Environmental Agency (EA) introduced an indicative groundwater discharge consent of 30/45/5 (BOD/SS/NH3 mg/l). Additionally, a new river discharge consent of 40/60 (BOD/SS mg/l) was set to take effect in March 2014. The existing WwTW could not meet these new standards, prompting Thames Water to plan for a new sewage treatment facility to ensure compliance with future discharge requirements to the River Thames.
The subcontractor was tasked with the outline design, detailed design, and construction of a new sewage works adjacent to the existing site, to be operational by 2026. The project had to be delivered as a 'turnkey' package, adhering to all Thames Water standards. Thames Water contractor Black and Veatch requested ARM Ltd to provide a suitable solution, considering the lack of power availability on-site.
Due to the lack of power, an aerated system was not feasible. ARM Ltd opted for a passive treatment solution, installing a 40 m³ septic tank, followed by a COPASAC chamber (with bypass), a siphon chamber for batch flow generation, and a 684 m² passive vertical flow reed bed system, which discharges into the local watercourse.
The new wastewater treatment system provides Thames Water with a no-power solution that meets the new EA consents, based on load predictions for 2026. This system offers secure treatment with a minimal carbon footprint, blending aesthetically with its location within Beale Park.
The award-winning new system at Lower Basildon provides a sustainable and cost-effective alternative to aerated wetland technology, meaning the treatment works can now meet EA consent levels despite the lack of onsite power.
