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After conducting a study of Salisbury Sewage Works, in support of an Odour Impact Assessment, we thought to share the layout for the greater good. Salisbury Waste Water Treatment Works (WWtW) take Foul and a good deal of Surface Water from Salisbury and surrounding settlements.
From Wikipedia: Salisbury is a cathedral city in Wiltshire, England, with a population of 40,302,[1] at the confluence of the rivers Avon, Nadder and Bourne. The city is approximately 20 miles (32 km) from Southampton and 30 miles (48 km) from Bath.
Location of Wessex Water Sewage Treatment Works
Bio logical filter is a bed of solid media for bacteria to attach on its surfaces. Wastewater is irrigated on the solid media . It is called a biological filter to emphasise that the filtration process is not mechanical straining of solids, but removal of organic substances by use of bacterial action.
Primary Settlement Tank (PST) The Primary Settlement or sedimentation tanks are designed to reduce the velocity of the wastewater flow, allowing heavier organic solids (called raw sludge) to settle. They are the first stage of treatment after the removal of rags and grit in the inlet works.
A tank in which settle able solids or humus is separated from the effluent flowing through it.
These provide buffer capacity in the event of a storm. A lot of rain water will flow through the plant during rainy periods, and if heavy the plant will not be able to keep up, and so sewage must be stored. Notes: Other Items not positioned include screens, macerators, dewatering, and various pumping stations.
Please click below image to enlarge annotated layout plan.
The below section was written by a machine.
The Salisbury Sewage Treatment Works (STW) is a critical piece of regional infrastructure operated by Wessex Water. Understanding the internal layout and processing stages of this facility is essential for developers and planners conducting high-precision environmental assessments in the Wiltshire area. This technical mapping resource provides clarity on the spatial distribution of treatment processes, which directly influences localized environmental factors such as air quality and water chemistry.
In the context of an odour impact assessment, the precise location of "active" sources—such as inlet works, primary settlement tanks, and sludge handling areas—is paramount. By utilizing detailed layout data, consultants can produce more accurate dispersion models that reflect the facility's actual footprint. This data is also vital for projects requiring a Environmental Impact Assessment (EIA) where the proximity of sensitive residential receptors must be scientifically evaluated against prevailing wind conditions, often utilizing regional datasets like the Yeovilton wind data.
The Salisbury STW discharges treated effluent into the Hampshire Avon catchment, a region highly sensitive to nutrient loading. Detailed knowledge of the plant’s configuration and discharge points is a core requirement for a robust Nutrient Neutrality Assessment and Mitigation Strategy (NNAMS). Developers must understand how their projects interface with local sewerage infrastructure to ensure compliance with nutrient neutrality mandates, particularly regarding the management of phosphates in protected river systems.
This layout should be viewed alongside our broader mapping of Wessex Water sewage treatment works across the South West. For industrial applications, the configuration of the STW also dictates the technical requirements for a discharge consent application or the design of a private effluent treatment plant. At Southwest Environmental Limited, we combine geospatial infrastructure data with over 15 years of industry experience to provide the technical authority required for complex planning and permitting challenges.