Chemical Industry
The history of brine extraction and its role in producing water treatment chemicals
Brine extraction in Britain, particularly in Cheshire, has a long industrial heritage that dates back to at least the Roman period and expanded markedly during the 18th and 19th centuries with industrialisation. Salt beds laid down by ancient seas underlie large parts of Cheshire; their accessibility and the demand for salt and related chemicals drove the development of brine pumping and refining technologies.
Key historical milestones
Early salt production: Surface salt pans and natural brine springs were exploited in Roman and medieval times. By the 1600s–1700s, commercial saltworks developed around natural springs and coastal evaporation sites.
Industrial Revolution expansion: From the late 18th century, Cheshire became a major centre for salt production. Advancements in steam power and deep-well pumping allowed extraction of large volumes of brine from subterranean rock salt seams.
Chemical industry birth: In the 19th century, the Solvay process, Leblanc process and later improvements transformed salt (sodium chloride) and brine derivatives into a wider range of chemical products. Chlor-alkali chemistry—electrolysis of brine to produce chlorine and caustic soda (sodium hydroxide)—became a foundation for many industrial chemical chains, including the manufacture of water treatment chemicals.
20th century modernisation: Electrolytic cell technology matured (mercury-cell, diaphragm-cell and membrane-cell processes), enabling higher-purity outputs and larger-scale production. Companies consolidated, and integrated chemical complexes developed adjacent to brine extraction sites to reduce transport costs and secure feedstock supply.
Post-war diversification and environmental pressure: The mid- to late 20th century saw diversification into a wider suite of chlorine-derived and sodium-derived compounds used in textiles, paper, plastics and water treatment. Increasing environmental regulation prompted shifts away from mercury cells and encouraged cleaner technologies.
Recent decades: Ownership changes, privatisation, and globalisation concentrated production in fewer, more efficient sites. Major operators in Cheshire built extensive brine extraction, purification and electrochemical processing plants that supply both commodity chemicals and specialist water-treatment products.
How brine becomes water treatment chemicals — the processing chain
Brine extraction
Solution mining / pumped brine: Freshwater is injected into salt beds to dissolve rock salt, creating a brine that is pumped to the surface. Alternatively, natural groundwater-saturated brine may be pumped from wells.
Mechanical pumping from saturated seams: In some sites, mechanical pumps bring naturally occurring brine to surface.
Brine quality control: Extracted brine contains dissolved salts (primarily sodium chloride) and impurities (gypsum, magnesium, organic matter). Initial on-site screening and sampling determine treatment needs.
Brine purification
Filtration and settling: Large particulates and suspended solids are removed by settling tanks and filtration.
Precipitation and ion exchange: Calcium and magnesium hardness are removed where necessary (e.g., via lime softening or chemical precipitation) to avoid fouling downstream electrolytic cells.
Evaporation/crystallisation (where applicable): For salt production, brine may be concentrated and evaporated to crystallise common salt, separating it from mother liquor for further processing.
Electrolysis (chlor-alkali process)
Cell types: Brine is fed to electrochemical cells—modern plants use membrane cells to split sodium chloride solution into chlorine gas at the anode and hydroxide ions at the cathode, producing hydrogen gas as a by-product and sodium hydroxide solution (caustic soda).
Product handling: Chlorine is captured, dried and compressed or liquified for use in downstream synthesis. Caustic soda is concentrated, stored, and transported as a liquid or solid (via evaporation to flakes or pellets).
Energy and environmental considerations: Electrolysis is energy-intensive. Technology upgrades focus on energy efficiency, reduced emissions and safer handling (replacing older mercury or diaphragm cells with membrane cells).
Further chemical synthesis and conversion
Chlorine derivatives: Chlorine is a feedstock for a wide range of chemicals—chlorinated solvents (historically), PVC (via ethylene dichloride and vinyl chloride monomer), and bleaching agents. For water treatment specifically, chlorine is used directly as a disinfectant (gaseous chlorine, sodium hypochlorite from chlorination of caustic solution, or bleaching powder).
Sodium hypochlorite and calcium hypochlorite: Chlorine can be reacted with caustic soda to form sodium hypochlorite, a common on-site water disinfectant. Calcium hypochlorite may be manufactured by further reaction and solidification routes.