Industry glossary
Terms you will meet in the documents, systems and scenarios.
Critical control point
A treatment or distribution step where control is essential to prevent or remove a hazard, monitored against a target, alert level and critical limit.
Free chlorine residual
The concentration of chlorine remaining in water after disinfection, measured in milligrams per litre, that continues to protect against contamination.
Turbidity
A measure of the cloudiness of water caused by suspended particles, reported in nephelometric turbidity units (NTU).
Contact time
The product of disinfectant concentration and the time water is in contact with it, used to verify that disinfection is adequate.
Filter-to-waste
The period after a backwash when filtered water is sent to waste until turbidity falls below the required level.
Activated sludge
A wastewater treatment process in which aerated micro-organisms consume organic matter and nutrients before being settled and partly returned.
Sludge volume index
A measure of how well activated sludge settles, calculated from the settled volume and the mixed liquor suspended solids.
Trade waste
Any liquid waste other than domestic sewage discharged to the sewer from commercial or industrial premises under an approval.
Confined space
An enclosed or partly enclosed space not designed for continuous occupancy with a risk from atmosphere, engulfment or restricted entry, such as a manhole or wet well.
Piezometer
An instrument installed in a dam embankment or foundation to measure water pressure, used to monitor seepage and dam safety.