R

Rainwater harvesting

Process of collecting and storing rainwater (3)

Raw water

Water that has not yet been treated (1)

Representative sample

Sample that has all the characteristics of the matter that it was taken from (12)

Residual chlorine

(in water treatment) the amount of chlorine left in water after all the pollutants have reacted with it (5)

Resilience

Ability to withstand shock, stress or a natural hazard (5)

Retention time

(in wastewater treatment) the time that effluent spends in a given environment, e.g. in a sedimentation tank or a stabilisation pond (11)

Risk

The chance of a hazard occurring (8)

Risk assessment

Process by which the likelihood of harm from a potential hazard is assessed (8)

Run-off

Rainwater that ‘runs off’ the land i.e. flows over the land surface (3)