New and repaired water mains must be chlorinated, flushed, and tested before they can be put into public supply. Chlorine is a highly toxic chemical that can cause severe respiratory distress and chemical burns even at low concentrations. The chlorination process also generates large volumes of heavily chlorinated wastewater that must be dechlorinated before discharge. This talk covers the safety controls for water main disinfection.
Key Hazards
Chlorine gas inhalation causing severe respiratory distress and lung damage
Chemical burns from concentrated sodium hypochlorite solution contact
Environmental pollution from discharging chlorinated water into watercourses
Pressurised fluid release from fittings failing during the flushing process
Control Measures
Review the COSHH assessment for sodium hypochlorite and all chlorination chemicals before use.
Wear chemical goggles, nitrile gloves, and a face shield when handling concentrated chlorine solution.
Mix chlorine solutions in a well-ventilated area and add chemical to water, never water to chemical.
Monitor chlorine vapour levels at the dosing and discharge points using a chlorine gas detector.
Dechlorinate all waste flushing water before discharging to any watercourse or surface drain.
Obtain an environmental permit or consent from the Environment Agency for all discharge operations.
Ensure emergency eyewash and safety shower are available at the chemical mixing location.
Brief all operatives on the chlorine emergency procedure and first aid for chemical contact.
Store chlorine chemicals in a secure, ventilated, bunded area away from other chemicals.
Emergency / Rescue
If chlorine solution contacts eyes or skin, flush with clean water for at least 20 minutes using the emergency shower or eyewash. If chlorine gas is inhaled, move to fresh air immediately. Call 999 for severe exposure.
Remember
Wear chemical goggles, gloves, and face shield when handling concentrated chlorine solutions
Always add chemical to water, never water to chemical, to prevent violent reactions
Monitor chlorine vapour levels at dosing and discharge points throughout the operation
Dechlorinate all waste flushing water before discharging to any watercourse or drain
Emergency eyewash and safety shower must be available at the mixing location
Applicable Legislation: COSHH 2002 · Water Supply (Water Quality) Regulations 2016 · Environmental Permitting Regulations 2016 · Health and Safety at Work etc. Act 1974