Background:
This profile looks at potential contaminants that may be associated with sewage treatment works and historical sewage farms. Sewage is a complex mixture of suspended and dissolved materials. Less than 0.1% of sewage consists of suspended solid material, the remainder is water. The chemical composition of incoming industrial effluents varies and may include heavy metals, solvents and pesticides.
This profile looks at potential contaminants that may be associated with sewage treatment works and historical sewage farms. Sewage is a complex mixture of suspended and dissolved materials. Less than 0.1% of sewage consists of suspended solid material, the remainder is water. The chemical composition of incoming industrial effluents varies and may include heavy metals, solvents and pesticides.
Potential Processes and Operations:
Several physical and biological treatment processes are undertaken at a sewage works or farm. The main principle is to separate the solid material from the liquid through different treatment steps such as screening, settling (sedimentation), filtration and aeration. Chemical additives may be used.
Several physical and biological treatment processes are undertaken at a sewage works or farm. The main principle is to separate the solid material from the liquid through different treatment steps such as screening, settling (sedimentation), filtration and aeration. Chemical additives may be used.
Sludges produced during separation need treatment to make final sludge disposal easier and safer and these treatment steps may include digestion, heat treatment, chemical conditioning, de-watering and heat drying.
Potential Contaminants of Concern:
| Contaminant type | Main group of contaminants | Location | |||||
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| Sewage works | Sewage farms | Sludge treatment/storage | Detritus storage/disposal | Pipework channels | Chemical storage | ||
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Organic |
Volatile organic compounds (VOCs) |
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| Halogenated hydrocarbons |
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| Non-halogenated hydrocarbons |
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| Polycyclic aromatic hydrocarbons (PAHs) |
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| Dioxins and furans |
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| Polychlorinated biphenyls (PCBs) | |||||||
| Pesticides and herbicides |
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| Organometallic compounds |
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| Explosives |
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Per- and polyfluoroalkyl substances (PFAS) |
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| Persistent organic pollutants (POPs) | • | • | • | • | |||
| Inorganic | Metals |
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| Non-metals and common inorganic substances |
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| Asbestos |
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| Cyanides |
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| Radionuclides |
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| Other potential contaminants of concern |
Microorganisms (pathogens) (e.g. Salmonella and Typhus bacteria) may be present. See original Industry Profile for additional information. Original profile does not include personal care products and pharmaceuticals which are a challenge for sewage treatment works.
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Original Industry Profile:
Further Information Sources:- British Water
- European Bureau for Research on Industrial Transformation and Emissions - Waste Treatment (2018)
-
PFAS Site Profile 11 - Wastewater Treatment Works (due to be published in summer 2026)
- US EPA - Biosolids
None.
