WWT/Process Areas/TBT-WWT-005

Chemical Dosing Area Safety

Water & Wastewater Treatment › Process Areas › Chemical Dosing Area Safety

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Chemical dosing areas on water and wastewater treatment works handle corrosive, toxic, and reactive substances for process treatment.
Common dosing chemicals include sodium hypochlorite, ferric sulphate, sodium hydroxide, polyelectrolyte, and sulphuric acid.
COSHH assessments must be prepared for every chemical used, specifying PPE, handling procedures, and emergency response.
Chemical storage must segregate incompatible substances — mixing certain chemicals causes violent reactions, toxic gas release, or fire.
Bulk chemical deliveries create additional hazards including tanker movements, pressurised transfers, and potential for overfilling.
Eye wash stations and emergency showers must be located within the immediate vicinity of all chemical dosing and storage areas.
Chemical-resistant PPE including goggles, face shields, gloves, and aprons must be worn during all handling and dosing operations.
Bunding around chemical storage must contain at least 110% of the largest vessel to prevent spills reaching drains or the environment.
Dosing pump maintenance requires LOTO isolation and drainage of chemical lines before disconnecting any pipework or components.
Chemical-specific spill kits must be available at every dosing area — oil-only absorbents do not work on acid or alkali spills.

Corrosive burns	Acids and alkalis cause severe chemical burns to skin and eyes within seconds of contact — PPE is the immediate barrier.
Incompatible mixing	Mixing certain chemicals produces violent reactions, toxic chlorine gas, or explosive compounds — segregation prevents catastrophic incidents.
Environmental pollution	Chemical spills reaching watercourses cause catastrophic ecological damage — bunding and spill response prevent environmental destruction.

Don't

Read the COSHH assessment for every chemical before handling or working in the dosing area.
Wear chemical-resistant goggles, gloves, face shield, and apron during all handling.
Segregate incompatible chemicals in storage according to their safety data sheets.
Know the location of the nearest eye wash station and emergency shower.
Supervise bulk chemical deliveries to prevent overfilling and tanker incidents.
Maintain bunding around chemical storage at 110% of the largest vessel capacity.
Follow LOTO procedures before maintaining dosing pumps or disconnecting chemical lines.
Keep chemical-specific spill kits stocked and accessible at every dosing area.
Report any chemical leak, spill, or equipment fault to the treatment works manager.
Attend chemical handling training before working in any dosing area on the works.

DON'T handle dosing chemicals without reading the COSHH assessment and wearing full PPE.
DON'T work in dosing areas without chemical-resistant goggles and gloves as a minimum.
DON'T store incompatible chemicals together — they react violently and release toxic gases.
DON'T work in dosing areas without knowing where the eye wash and emergency shower are.
DON'T leave bulk deliveries unsupervised — overfills cause major chemical spills.
DON'T allow bunding to become damaged or compromised — it contains the entire spill volume.
DON'T work on dosing pumps without LOTO isolation and chemical line drainage.
DON'T use oil-only spill kits on acid or alkali spills — use the correct chemical kit.
DON'T ignore small leaks — they indicate equipment failure that will worsen rapidly.
DON'T enter dosing areas without chemical handling training appropriate to the substances.

See also: COSHH Awareness | Wastewater Treatment Works Safety Awareness

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