Australian Drinking Water Guidelines Resources

Vulnerability 
Class 1

Fully protected catchment and large storage reservoir ⁽¹⁾

(> I GL)

Negligible or preferably none.

No sewage treatment plants.

No on-site sewage management systems within the protected part of the catchment.

Natural bushland protection is supported by enforced regulation and land planning controls.

Proactive surveillance and management regime to reduce impact of feral animals (where practical).

Low intensity/low risk activities may be allowed in the outer catchment, but active source protection (e.g. ranger surveillance) is practised to ensure negligible contamination risk.

Supply is drawn from a large reservoir.⁽¹⁾

The catchment area for the source water is essentially free of humans or ruminant livestock as sources of enteric pathogens (including protozoa, viruses and bacteria).

Sources of microbial contaminants include birds (e.g. water fowl) and native and feral animals (predominantly although not exclusively enteric bacteria).

The risks from these contaminants can be mitigated by storing the source water in a large raw water storage reservoir, which allows time for die off and/or settling.

The turbidity of the source water is low enough at the offtake point that it does not compromise effective disinfection.⁽³⁾

Negligible or preferably none.

No activities involving primary or secondary water contact.

Negligible stock animal populations.

No farms.

Limited (monitored and controlled) populations of feral animals.

Vulnerability 
Class 2

Moderately protected catchment with well protected inner catchment

OR

Protected catchment with run of river extraction

OR

with storage reservoirs that hold >1 GL (or more than one year's annual flow)

Public access, such as recreational activities

Stock animals

Minimal.

No sewage treatment plants.

Low density rural developments with well-managed on-site sewage management systems.

Active source protection (e.g. ranger surveillance) is practiced to minimise contamination risk.

Stock are fully fenced out of main feeder streams to the reservoir, and these streams are lined with vegetated buffer zones.

Natural bushland inner catchment area, low-density rural outer catchment area. Protection supported by enforced regulation in the inner catchment area.

Supply may be from a large or small reservoir or run of the river.⁽¹⁾

The catchment area for the source water has minimal sources of enteric pathogens derived from humans or livestock (including protozoa, viruses and bacteria).

Higher concentrations of indicator bacteria than a Category 1 source water are likely to be observed at the offtake point because of:

• the absence of a large raw water storage reservoir (in some cases) that would assist with the die off and/or settling of any pathogens that may be present
• some minor sources of human habitation (e.g. rural subdivisions) and livestock contamination are present in remote parts of the catchment, but they are sufficiently distant from the offtake point, or are well buffered by the presence of riparian vegetation, to not present a major microbial risk.

Land-based public access such as for recreation (camping, biking, four-wheel driving).

Primary and secondary water contact activities.

Low population size and density.

No sources of intensive animal husbandry (e.g. diaries, feedlots, piggeries).

Vulnerability 
Class 3

Poorly protected
outer catchment
with moderate
protection of the
inner catchment

Public access,
such as for
recreational
activities

Stock animals

Moderate population size and density.

May include limited sewered urban areas and sewage treatment plants within the outer catchment area.

Medium density rural development in outer catchment, possibly including some limited areas of urban development (e.g. small towns, satellite suburbs).

Human settlements excluded from inner catchment area.

Limited catchment management interventions (e.g. stream fencing, on-site sewage management system inspection and maintenance programs, stream frontage riparian buffers, planning overlays and other planning controls). 

Source protection supported by active surveillance in the inner catchment area.

Major sewer overflows or sewage treatment plants failures into source water are reportable to the downstream water treatment plant operator.

Supply may be from a large or small reservoir or be run of the river.⁽¹⁾

The catchment area for the source water has multiple sources of faecal contamination from humans (e.g. urban subdivisions, contributing stormwater runoff, or through the presence of onsite wastewater treatment systems) and livestock are present in a large proportion of the outer catchment and may have access to main feeder streams.

The inner catchment area, and any raw water storage that may be present, are protected from faecal contamination.

Moderate level of land-based public access such as for recreation (camping, biking, four wheel driving).

Secondary and primary water contact activities.

Vulnerability 
Class 4

Unprotected catchment

OR

Moderately protected and poorly protected catchments with no protected inner catchment

Public access,
such as for
recreational
activities

Stock animals

High density urban areas and large population size (e.g. large towns, suburbs).

Includes sewered urban areas and sewage treatment plants within the catchment area

Limited management interventions in the outer and inner catchment areas ⁽²⁾ (e.g. stream fencing, on-site sewage management system inspection and maintenance programs, stream frontage riparian buffers, and planning controls.)

Major sewer overflows or sewage treatment plant failures into source water are reportable to the downstream water treatment plant operator.

Supply may be sourced from a large or small reservoir or run of the river.⁽¹⁾

The catchment area for the source water has multiple sources of faecal contamination from both human and agricultural activities.

The inner catchment area is not protected and recreational activities (primary or secondary water contact) are permitted throughout the catchment or on any raw water storage that may be present.

There are limited protection measures applied.

Land-based public access such as for recreation (camping, biking, four-wheel driving) in both the outer and inner catchment⁽²⁾ (away from urban developments).

May include water-based recreation on reservoirs.

Potentially high densities in both outer and inner catchment areas⁽²⁾ (away from urban developments).

There are sources of intensive animal husbandry (e.g. dairies, feedlots, piggeries) within the catchment area.

Accepted industry norms.²

Performance depends on design, management and operational effectiveness and good supporting practices. On-line monitoring of filtered water turbidities; maintaining turbidities below defined critical limits measured by nephelometric turbidity units (NTU) (e.g. <0.2 NTU); minimising turbidity spikes and controlling filter backwash and recycling procedures are consistent with achieving higher LRVs.

Lack of sedimentation in direct filtration reduces maximum removals by 0.5-1 LRV.

Published validation protocol.³

Maintaining individual filter turbidities below defined critical limits (e.g. ≤ 0.1 NTU).

Daily Membrane Integrity Test (MIT) to manufacturer’s specification for the required LRV.

UF typically achieves higher LRVs.

Published inactivation data and validation protocol.⁴

Virus
C.t_99.99 6 mg.min/L at pH 7, 10°C, turbidity <2 NTU⁵
C.t_99.99 16 mg.min/L at pH 8, 10°C and turbidity <2 NTU⁵

Bacteria
C.t_99.99 <1 mg.min/L at pH 6-9, 10°C-15°C, and turbidity ≤1NTU.⁵

For bacteria and viruses, a default of 15 mg.min/L is given as an acceptable value in the Guidelines

(See also Information Sheet 1.3).

Published inactivation data.⁶

Virus
C.t_99.99 3100 mg.min/L at pH 7, 10°C, turbidity ≤2NTU⁵
C.t_99.99 3970 mg.min/L at pH 8, 10°C, turbidity ≤2NTU⁵
C.t_99.99 6870 mg.min/L at pH 9, 10°C, turbidity ≤2NTU⁵

Bacteria
C.t_99.99 360 mg.min/L at pH 8-9, ≥5°C, turbidity ≤1NTU⁵

(See also Information Sheet 1.4).

Published inactivation data and validation protocol.⁷

UV dose of 186 mJ/cm² can provide 4 log inactivation of viruses and 22 mJ/cm² can provide 4 log inactivation of protozoa and bacteria.

(See also Information Sheet 1.7)

Published inactivation data and validation protocol.⁸

Virus
C.t_99.99 ≥1.2 mg.min/L at pH 6-9, ≥5°C, turbidity ≤1NTU

Protozoa⁵
C.t_99.99 ≥64 mg.min/L at pH 6-9, ≥5°C, turbidity ≤1NTU

Bacteria⁵
C.t_99.99 ≥0.04 mg.min/L at pH 6-9, ≥5°C, turbidity ≤1NTU⁵

(See also Information Sheet 1.6)

1.5-2

2.5-4

1.5-2

2.5-4

1.5-2

2.5-4

Published validation protocol.⁹

Validated LRVs limited by sensitivity of operational monitoring.

Based on on-line operational monitoring of EC or TOC.

Based on on-line or off-line operational monitoring of sulphate or fluorescent dyes.

Online, continuous chlorine residual analyser, flow and pH

24-hour monitored alarms on residual monitoring, pH and chlorine dosing equipment

Regular turbidity and temperature monitoring, and chlorine demand calculations. Increase frequency on changing water quality

Appropriate electronic or hard copy monitoring records

Online, continuous chlorine residual analyser, flow and pH

24-hour monitored alarms on residual monitoring, pH and chlorine dosing equipment

Regular turbidity and temperature monitoring, and chlorine demand calculations. Increase frequency on changing water quality

Appropriate electronic or hard copy monitoring records