The Water Pollution Act (1977) defined a ‘trade effluent’ as an effluent, “which is discharged from premises used for carrying on any trade or industry (including mining) but does not include domestic sewage or storm water”.
- All ‘trade effluents’ must be licensed.
- Discharges of domestic-type wastewater (sewage) from commercial and industrial premises to municipal sewers is generally not subject to licence but a licence would be required if the discharge is directly to a surface water.
- Discharges of other-type wastewater (eg. canteen, process water, commercial floor cleaning etc.) from commercial and industrial premises is normally subject to licence to for discharges to either sewer or surface water.
- A licence is not required for domestic sewage not exceeding a volume of 5m3 in any period of 24 hours that is discharged to an aquifer from a septic tank or other disposal unit by means of a percolation area, soakage pit or other method.
- A licence is required for discharge of domestic sewage from a septic tank where the discharge is direct to surface waters and, in all cases where the discharge exceeds 5m3 in 24 hours.
- Many industrial processes do not generate ‘process wastewater’ or effluent but may discharge other waters, eg. uncontaminated cooling water, boiler make-up or blow-down water. These would regarded as wastewater may contains various treatment chemical additives.
In general, the licencing authorities do not grant licences for discharges of uncontaminated storm water (rain water) to either municipal sewers or watercourses since such discharges are non-polluting.
- However, a licencing authority may decide that storm water from paved areas where there is a risk of pollution (e.g., loading or unloading of liquid materials or chemical substances) should be licensed.